Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 3871 insertions, 0 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
new file mode 100644
index 000000000..712948e97
--- /dev/null
+++ b/fs/proc/base.c
@@ -0,0 +1,3871 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  linux/fs/proc/base.c
+ *
+ *  Copyright (C) 1991, 1992 Linus Torvalds
+ *
+ *  proc base directory handling functions
+ *
+ *  1999, Al Viro. Rewritten. Now it covers the whole per-process part.
+ *  Instead of using magical inumbers to determine the kind of object
+ *  we allocate and fill in-core inodes upon lookup. They don't even
+ *  go into icache. We cache the reference to task_struct upon lookup too.
+ *  Eventually it should become a filesystem in its own. We don't use the
+ *  rest of procfs anymore.
+ *
+ *
+ *  Changelog:
+ *  17-Jan-2005
+ *  Allan Bezerra
+ *  Bruna Moreira <bruna.moreira@indt.org.br>
+ *  Edjard Mota <edjard.mota@indt.org.br>
+ *  Ilias Biris <ilias.biris@indt.org.br>
+ *  Mauricio Lin <mauricio.lin@indt.org.br>
+ *
+ *  Embedded Linux Lab - 10LE Instituto Nokia de Tecnologia - INdT
+ *
+ *  A new process specific entry (smaps) included in /proc. It shows the
+ *  size of rss for each memory area. The maps entry lacks information
+ *  about physical memory size (rss) for each mapped file, i.e.,
+ *  rss information for executables and library files.
+ *  This additional information is useful for any tools that need to know
+ *  about physical memory consumption for a process specific library.
+ *
+ *  Changelog:
+ *  21-Feb-2005
+ *  Embedded Linux Lab - 10LE Instituto Nokia de Tecnologia - INdT
+ *  Pud inclusion in the page table walking.
+ *
+ *  ChangeLog:
+ *  10-Mar-2005
+ *  10LE Instituto Nokia de Tecnologia - INdT:
+ *  A better way to walks through the page table as suggested by Hugh Dickins.
+ *
+ *  Simo Piiroinen <simo.piiroinen@nokia.com>:
+ *  Smaps information related to shared, private, clean and dirty pages.
+ *
+ *  Paul Mundt <paul.mundt@nokia.com>:
+ *  Overall revision about smaps.
+ */
+
+#include <linux/uaccess.h>
+
+#include <linux/errno.h>
+#include <linux/time.h>
+#include <linux/proc_fs.h>
+#include <linux/stat.h>
+#include <linux/task_io_accounting_ops.h>
+#include <linux/init.h>
+#include <linux/capability.h>
+#include <linux/file.h>
+#include <linux/fdtable.h>
+#include <linux/generic-radix-tree.h>
+#include <linux/string.h>
+#include <linux/seq_file.h>
+#include <linux/namei.h>
+#include <linux/mnt_namespace.h>
+#include <linux/mm.h>
+#include <linux/swap.h>
+#include <linux/rcupdate.h>
+#include <linux/kallsyms.h>
+#include <linux/stacktrace.h>
+#include <linux/resource.h>
+#include <linux/module.h>
+#include <linux/mount.h>
+#include <linux/security.h>
+#include <linux/ptrace.h>
+#include <linux/tracehook.h>
+#include <linux/printk.h>
+#include <linux/cache.h>
+#include <linux/cgroup.h>
+#include <linux/cpuset.h>
+#include <linux/audit.h>
+#include <linux/poll.h>
+#include <linux/nsproxy.h>
+#include <linux/oom.h>
+#include <linux/elf.h>
+#include <linux/pid_namespace.h>
+#include <linux/user_namespace.h>
+#include <linux/fs_struct.h>
+#include <linux/slab.h>
+#include <linux/sched/autogroup.h>
+#include <linux/sched/mm.h>
+#include <linux/sched/coredump.h>
+#include <linux/sched/debug.h>
+#include <linux/sched/stat.h>
+#include <linux/posix-timers.h>
+#include <linux/time_namespace.h>
+#include <linux/resctrl.h>
+#include <trace/events/oom.h>
+#include "internal.h"
+#include "fd.h"
+
+#include "../../lib/kstrtox.h"
+
+/* NOTE:
+ *	Implementing inode permission operations in /proc is almost
+ *	certainly an error.  Permission checks need to happen during
+ *	each system call not at open time.  The reason is that most of
+ *	what we wish to check for permissions in /proc varies at runtime.
+ *
+ *	The classic example of a problem is opening file descriptors
+ *	in /proc for a task before it execs a suid executable.
+ */
+
+static u8 nlink_tid __ro_after_init;
+static u8 nlink_tgid __ro_after_init;
+
+struct pid_entry {
+	const char *name;
+	unsigned int len;
+	umode_t mode;
+	const struct inode_operations *iop;
+	const struct file_operations *fop;
+	union proc_op op;
+};
+
+#define NOD(NAME, MODE, IOP, FOP, OP) {			\
+	.name = (NAME),					\
+	.len  = sizeof(NAME) - 1,			\
+	.mode = MODE,					\
+	.iop  = IOP,					\
+	.fop  = FOP,					\
+	.op   = OP,					\
+}
+
+#define DIR(NAME, MODE, iops, fops)	\
+	NOD(NAME, (S_IFDIR|(MODE)), &iops, &fops, {} )
+#define LNK(NAME, get_link)					\
+	NOD(NAME, (S_IFLNK|S_IRWXUGO),				\
+		&proc_pid_link_inode_operations, NULL,		\
+		{ .proc_get_link = get_link } )
+#define REG(NAME, MODE, fops)				\
+	NOD(NAME, (S_IFREG|(MODE)), NULL, &fops, {})
+#define ONE(NAME, MODE, show)				\
+	NOD(NAME, (S_IFREG|(MODE)),			\
+		NULL, &proc_single_file_operations,	\
+		{ .proc_show = show } )
+#define ATTR(LSM, NAME, MODE)				\
+	NOD(NAME, (S_IFREG|(MODE)),			\
+		NULL, &proc_pid_attr_operations,	\
+		{ .lsm = LSM })
+
+/*
+ * Count the number of hardlinks for the pid_entry table, excluding the .
+ * and .. links.
+ */
+static unsigned int __init pid_entry_nlink(const struct pid_entry *entries,
+	unsigned int n)
+{
+	unsigned int i;
+	unsigned int count;
+
+	count = 2;
+	for (i = 0; i < n; ++i) {
+		if (S_ISDIR(entries[i].mode))
+			++count;
+	}
+
+	return count;
+}
+
+static int get_task_root(struct task_struct *task, struct path *root)
+{
+	int result = -ENOENT;
+
+	task_lock(task);
+	if (task->fs) {
+		get_fs_root(task->fs, root);
+		result = 0;
+	}
+	task_unlock(task);
+	return result;
+}
+
+static int proc_cwd_link(struct dentry *dentry, struct path *path)
+{
+	struct task_struct *task = get_proc_task(d_inode(dentry));
+	int result = -ENOENT;
+
+	if (task) {
+		task_lock(task);
+		if (task->fs) {
+			get_fs_pwd(task->fs, path);
+			result = 0;
+		}
+		task_unlock(task);
+		put_task_struct(task);
+	}
+	return result;
+}
+
+static int proc_root_link(struct dentry *dentry, struct path *path)
+{
+	struct task_struct *task = get_proc_task(d_inode(dentry));
+	int result = -ENOENT;
+
+	if (task) {
+		result = get_task_root(task, path);
+		put_task_struct(task);
+	}
+	return result;
+}
+
+/*
+ * If the user used setproctitle(), we just get the string from
+ * user space at arg_start, and limit it to a maximum of one page.
+ */
+static ssize_t get_mm_proctitle(struct mm_struct *mm, char __user *buf,
+				size_t count, unsigned long pos,
+				unsigned long arg_start)
+{
+	char *page;
+	int ret, got;
+
+	if (pos >= PAGE_SIZE)
+		return 0;
+
+	page = (char *)__get_free_page(GFP_KERNEL);
+	if (!page)
+		return -ENOMEM;
+
+	ret = 0;
+	got = access_remote_vm(mm, arg_start, page, PAGE_SIZE, FOLL_ANON);
+	if (got > 0) {
+		int len = strnlen(page, got);
+
+		/* Include the NUL character if it was found */
+		if (len < got)
+			len++;
+
+		if (len > pos) {
+			len -= pos;
+			if (len > count)
+				len = count;
+			len -= copy_to_user(buf, page+pos, len);
+			if (!len)
+				len = -EFAULT;
+			ret = len;
+		}
+	}
+	free_page((unsigned long)page);
+	return ret;
+}
+
+static ssize_t get_mm_cmdline(struct mm_struct *mm, char __user *buf,
+			      size_t count, loff_t *ppos)
+{
+	unsigned long arg_start, arg_end, env_start, env_end;
+	unsigned long pos, len;
+	char *page, c;
+
+	/* Check if process spawned far enough to have cmdline. */
+	if (!mm->env_end)
+		return 0;
+
+	spin_lock(&mm->arg_lock);
+	arg_start = mm->arg_start;
+	arg_end = mm->arg_end;
+	env_start = mm->env_start;
+	env_end = mm->env_end;
+	spin_unlock(&mm->arg_lock);
+
+	if (arg_start >= arg_end)
+		return 0;
+
+	/*
+	 * We allow setproctitle() to overwrite the argument
+	 * strings, and overflow past the original end. But
+	 * only when it overflows into the environment area.
+	 */
+	if (env_start != arg_end || env_end < env_start)
+		env_start = env_end = arg_end;
+	len = env_end - arg_start;
+
+	/* We're not going to care if "*ppos" has high bits set */
+	pos = *ppos;
+	if (pos >= len)
+		return 0;
+	if (count > len - pos)
+		count = len - pos;
+	if (!count)
+		return 0;
+
+	/*
+	 * Magical special case: if the argv[] end byte is not
+	 * zero, the user has overwritten it with setproctitle(3).
+	 *
+	 * Possible future enhancement: do this only once when
+	 * pos is 0, and set a flag in the 'struct file'.
+	 */
+	if (access_remote_vm(mm, arg_end-1, &c, 1, FOLL_ANON) == 1 && c)
+		return get_mm_proctitle(mm, buf, count, pos, arg_start);
+
+	/*
+	 * For the non-setproctitle() case we limit things strictly
+	 * to the [arg_start, arg_end[ range.
+	 */
+	pos += arg_start;
+	if (pos < arg_start || pos >= arg_end)
+		return 0;
+	if (count > arg_end - pos)
+		count = arg_end - pos;
+
+	page = (char *)__get_free_page(GFP_KERNEL);
+	if (!page)
+		return -ENOMEM;
+
+	len = 0;
+	while (count) {
+		int got;
+		size_t size = min_t(size_t, PAGE_SIZE, count);
+
+		got = access_remote_vm(mm, pos, page, size, FOLL_ANON);
+		if (got <= 0)
+			break;
+		got -= copy_to_user(buf, page, got);
+		if (unlikely(!got)) {
+			if (!len)
+				len = -EFAULT;
+			break;
+		}
+		pos += got;
+		buf += got;
+		len += got;
+		count -= got;
+	}
+
+	free_page((unsigned long)page);
+	return len;
+}
+
+static ssize_t get_task_cmdline(struct task_struct *tsk, char __user *buf,
+				size_t count, loff_t *pos)
+{
+	struct mm_struct *mm;
+	ssize_t ret;
+
+	mm = get_task_mm(tsk);
+	if (!mm)
+		return 0;
+
+	ret = get_mm_cmdline(mm, buf, count, pos);
+	mmput(mm);
+	return ret;
+}
+
+static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf,
+				     size_t count, loff_t *pos)
+{
+	struct task_struct *tsk;
+	ssize_t ret;
+
+	BUG_ON(*pos < 0);
+
+	tsk = get_proc_task(file_inode(file));
+	if (!tsk)
+		return -ESRCH;
+	ret = get_task_cmdline(tsk, buf, count, pos);
+	put_task_struct(tsk);
+	if (ret > 0)
+		*pos += ret;
+	return ret;
+}
+
+static const struct file_operations proc_pid_cmdline_ops = {
+	.read	= proc_pid_cmdline_read,
+	.llseek	= generic_file_llseek,
+};
+
+#ifdef CONFIG_KALLSYMS
+/*
+ * Provides a wchan file via kallsyms in a proper one-value-per-file format.
+ * Returns the resolved symbol.  If that fails, simply return the address.
+ */
+static int proc_pid_wchan(struct seq_file *m, struct pid_namespace *ns,
+			  struct pid *pid, struct task_struct *task)
+{
+	unsigned long wchan;
+	char symname[KSYM_NAME_LEN];
+
+	if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
+		goto print0;
+
+	wchan = get_wchan(task);
+	if (wchan && !lookup_symbol_name(wchan, symname)) {
+		seq_puts(m, symname);
+		return 0;
+	}
+
+print0:
+	seq_putc(m, '0');
+	return 0;
+}
+#endif /* CONFIG_KALLSYMS */
+
+static int lock_trace(struct task_struct *task)
+{
+	int err = down_read_killable(&task->signal->exec_update_lock);
+	if (err)
+		return err;
+	if (!ptrace_may_access(task, PTRACE_MODE_ATTACH_FSCREDS)) {
+		up_read(&task->signal->exec_update_lock);
+		return -EPERM;
+	}
+	return 0;
+}
+
+static void unlock_trace(struct task_struct *task)
+{
+	up_read(&task->signal->exec_update_lock);
+}
+
+#ifdef CONFIG_STACKTRACE
+
+#define MAX_STACK_TRACE_DEPTH	64
+
+static int proc_pid_stack(struct seq_file *m, struct pid_namespace *ns,
+			  struct pid *pid, struct task_struct *task)
+{
+	unsigned long *entries;
+	int err;
+
+	/*
+	 * The ability to racily run the kernel stack unwinder on a running task
+	 * and then observe the unwinder output is scary; while it is useful for
+	 * debugging kernel issues, it can also allow an attacker to leak kernel
+	 * stack contents.
+	 * Doing this in a manner that is at least safe from races would require
+	 * some work to ensure that the remote task can not be scheduled; and
+	 * even then, this would still expose the unwinder as local attack
+	 * surface.
+	 * Therefore, this interface is restricted to root.
+	 */
+	if (!file_ns_capable(m->file, &init_user_ns, CAP_SYS_ADMIN))
+		return -EACCES;
+
+	entries = kmalloc_array(MAX_STACK_TRACE_DEPTH, sizeof(*entries),
+				GFP_KERNEL);
+	if (!entries)
+		return -ENOMEM;
+
+	err = lock_trace(task);
+	if (!err) {
+		unsigned int i, nr_entries;
+
+		nr_entries = stack_trace_save_tsk(task, entries,
+						  MAX_STACK_TRACE_DEPTH, 0);
+
+		for (i = 0; i < nr_entries; i++) {
+			seq_printf(m, "[<0>] %pB\n", (void *)entries[i]);
+		}
+
+		unlock_trace(task);
+	}
+	kfree(entries);
+
+	return err;
+}
+#endif
+
+#ifdef CONFIG_SCHED_INFO
+/*
+ * Provides /proc/PID/schedstat
+ */
+static int proc_pid_schedstat(struct seq_file *m, struct pid_namespace *ns,
+			      struct pid *pid, struct task_struct *task)
+{
+	if (unlikely(!sched_info_on()))
+		seq_puts(m, "0 0 0\n");
+	else
+		seq_printf(m, "%llu %llu %lu\n",
+		   (unsigned long long)task->se.sum_exec_runtime,
+		   (unsigned long long)task->sched_info.run_delay,
+		   task->sched_info.pcount);
+
+	return 0;
+}
+#endif
+
+#ifdef CONFIG_LATENCYTOP
+static int lstats_show_proc(struct seq_file *m, void *v)
+{
+	int i;
+	struct inode *inode = m->private;
+	struct task_struct *task = get_proc_task(inode);
+
+	if (!task)
+		return -ESRCH;
+	seq_puts(m, "Latency Top version : v0.1\n");
+	for (i = 0; i < LT_SAVECOUNT; i++) {
+		struct latency_record *lr = &task->latency_record[i];
+		if (lr->backtrace[0]) {
+			int q;
+			seq_printf(m, "%i %li %li",
+				   lr->count, lr->time, lr->max);
+			for (q = 0; q < LT_BACKTRACEDEPTH; q++) {
+				unsigned long bt = lr->backtrace[q];
+
+				if (!bt)
+					break;
+				seq_printf(m, " %ps", (void *)bt);
+			}
+			seq_putc(m, '\n');
+		}
+
+	}
+	put_task_struct(task);
+	return 0;
+}
+
+static int lstats_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, lstats_show_proc, inode);
+}
+
+static ssize_t lstats_write(struct file *file, const char __user *buf,
+			    size_t count, loff_t *offs)
+{
+	struct task_struct *task = get_proc_task(file_inode(file));
+
+	if (!task)
+		return -ESRCH;
+	clear_tsk_latency_tracing(task);
+	put_task_struct(task);
+
+	return count;
+}
+
+static const struct file_operations proc_lstats_operations = {
+	.open		= lstats_open,
+	.read		= seq_read,
+	.write		= lstats_write,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
+#endif
+
+static int proc_oom_score(struct seq_file *m, struct pid_namespace *ns,
+			  struct pid *pid, struct task_struct *task)
+{
+	unsigned long totalpages = totalram_pages() + total_swap_pages;
+	unsigned long points = 0;
+	long badness;
+
+	badness = oom_badness(task, totalpages);
+	/*
+	 * Special case OOM_SCORE_ADJ_MIN for all others scale the
+	 * badness value into [0, 2000] range which we have been
+	 * exporting for a long time so userspace might depend on it.
+	 */
+	if (badness != LONG_MIN)
+		points = (1000 + badness * 1000 / (long)totalpages) * 2 / 3;
+
+	seq_printf(m, "%lu\n", points);
+
+	return 0;
+}
+
+struct limit_names {
+	const char *name;
+	const char *unit;
+};
+
+static const struct limit_names lnames[RLIM_NLIMITS] = {
+	[RLIMIT_CPU] = {"Max cpu time", "seconds"},
+	[RLIMIT_FSIZE] = {"Max file size", "bytes"},
+	[RLIMIT_DATA] = {"Max data size", "bytes"},
+	[RLIMIT_STACK] = {"Max stack size", "bytes"},
+	[RLIMIT_CORE] = {"Max core file size", "bytes"},
+	[RLIMIT_RSS] = {"Max resident set", "bytes"},
+	[RLIMIT_NPROC] = {"Max processes", "processes"},
+	[RLIMIT_NOFILE] = {"Max open files", "files"},
+	[RLIMIT_MEMLOCK] = {"Max locked memory", "bytes"},
+	[RLIMIT_AS] = {"Max address space", "bytes"},
+	[RLIMIT_LOCKS] = {"Max file locks", "locks"},
+	[RLIMIT_SIGPENDING] = {"Max pending signals", "signals"},
+	[RLIMIT_MSGQUEUE] = {"Max msgqueue size", "bytes"},
+	[RLIMIT_NICE] = {"Max nice priority", NULL},
+	[RLIMIT_RTPRIO] = {"Max realtime priority", NULL},
+	[RLIMIT_RTTIME] = {"Max realtime timeout", "us"},
+};
+
+/* Display limits for a process */
+static int proc_pid_limits(struct seq_file *m, struct pid_namespace *ns,
+			   struct pid *pid, struct task_struct *task)
+{
+	unsigned int i;
+	unsigned long flags;
+
+	struct rlimit rlim[RLIM_NLIMITS];
+
+	if (!lock_task_sighand(task, &flags))
+		return 0;
+	memcpy(rlim, task->signal->rlim, sizeof(struct rlimit) * RLIM_NLIMITS);
+	unlock_task_sighand(task, &flags);
+
+	/*
+	 * print the file header
+	 */
+	seq_puts(m, "Limit                     "
+		"Soft Limit           "
+		"Hard Limit           "
+		"Units     \n");
+
+	for (i = 0; i < RLIM_NLIMITS; i++) {
+		if (rlim[i].rlim_cur == RLIM_INFINITY)
+			seq_printf(m, "%-25s %-20s ",
+				   lnames[i].name, "unlimited");
+		else
+			seq_printf(m, "%-25s %-20lu ",
+				   lnames[i].name, rlim[i].rlim_cur);
+
+		if (rlim[i].rlim_max == RLIM_INFINITY)
+			seq_printf(m, "%-20s ", "unlimited");
+		else
+			seq_printf(m, "%-20lu ", rlim[i].rlim_max);
+
+		if (lnames[i].unit)
+			seq_printf(m, "%-10s\n", lnames[i].unit);
+		else
+			seq_putc(m, '\n');
+	}
+
+	return 0;
+}
+
+#ifdef CONFIG_HAVE_ARCH_TRACEHOOK
+static int proc_pid_syscall(struct seq_file *m, struct pid_namespace *ns,
+			    struct pid *pid, struct task_struct *task)
+{
+	struct syscall_info info;
+	u64 *args = &info.data.args[0];
+	int res;
+
+	res = lock_trace(task);
+	if (res)
+		return res;
+
+	if (task_current_syscall(task, &info))
+		seq_puts(m, "running\n");
+	else if (info.data.nr < 0)
+		seq_printf(m, "%d 0x%llx 0x%llx\n",
+			   info.data.nr, info.sp, info.data.instruction_pointer);
+	else
+		seq_printf(m,
+		       "%d 0x%llx 0x%llx 0x%llx 0x%llx 0x%llx 0x%llx 0x%llx 0x%llx\n",
+		       info.data.nr,
+		       args[0], args[1], args[2], args[3], args[4], args[5],
+		       info.sp, info.data.instruction_pointer);
+	unlock_trace(task);
+
+	return 0;
+}
+#endif /* CONFIG_HAVE_ARCH_TRACEHOOK */
+
+/************************************************************************/
+/*                       Here the fs part begins                        */
+/************************************************************************/
+
+/* permission checks */
+static int proc_fd_access_allowed(struct inode *inode)
+{
+	struct task_struct *task;
+	int allowed = 0;
+	/* Allow access to a task's file descriptors if it is us or we
+	 * may use ptrace attach to the process and find out that
+	 * information.
+	 */
+	task = get_proc_task(inode);
+	if (task) {
+		allowed = ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS);
+		put_task_struct(task);
+	}
+	return allowed;
+}
+
+int proc_setattr(struct dentry *dentry, struct iattr *attr)
+{
+	int error;
+	struct inode *inode = d_inode(dentry);
+
+	if (attr->ia_valid & ATTR_MODE)
+		return -EPERM;
+
+	error = setattr_prepare(dentry, attr);
+	if (error)
+		return error;
+
+	setattr_copy(inode, attr);
+	mark_inode_dirty(inode);
+	return 0;
+}
+
+/*
+ * May current process learn task's sched/cmdline info (for hide_pid_min=1)
+ * or euid/egid (for hide_pid_min=2)?
+ */
+static bool has_pid_permissions(struct proc_fs_info *fs_info,
+				 struct task_struct *task,
+				 enum proc_hidepid hide_pid_min)
+{
+	/*
+	 * If 'hidpid' mount option is set force a ptrace check,
+	 * we indicate that we are using a filesystem syscall
+	 * by passing PTRACE_MODE_READ_FSCREDS
+	 */
+	if (fs_info->hide_pid == HIDEPID_NOT_PTRACEABLE)
+		return ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS);
+
+	if (fs_info->hide_pid < hide_pid_min)
+		return true;
+	if (in_group_p(fs_info->pid_gid))
+		return true;
+	return ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS);
+}
+
+
+static int proc_pid_permission(struct inode *inode, int mask)
+{
+	struct proc_fs_info *fs_info = proc_sb_info(inode->i_sb);
+	struct task_struct *task;
+	bool has_perms;
+
+	task = get_proc_task(inode);
+	if (!task)
+		return -ESRCH;
+	has_perms = has_pid_permissions(fs_info, task, HIDEPID_NO_ACCESS);
+	put_task_struct(task);
+
+	if (!has_perms) {
+		if (fs_info->hide_pid == HIDEPID_INVISIBLE) {
+			/*
+			 * Let's make getdents(), stat(), and open()
+			 * consistent with each other.  If a process
+			 * may not stat() a file, it shouldn't be seen
+			 * in procfs at all.
+			 */
+			return -ENOENT;
+		}
+
+		return -EPERM;
+	}
+	return generic_permission(inode, mask);
+}
+
+
+
+static const struct inode_operations proc_def_inode_operations = {
+	.setattr	= proc_setattr,
+};
+
+static int proc_single_show(struct seq_file *m, void *v)
+{
+	struct inode *inode = m->private;
+	struct pid_namespace *ns = proc_pid_ns(inode->i_sb);
+	struct pid *pid = proc_pid(inode);
+	struct task_struct *task;
+	int ret;
+
+	task = get_pid_task(pid, PIDTYPE_PID);
+	if (!task)
+		return -ESRCH;
+
+	ret = PROC_I(inode)->op.proc_show(m, ns, pid, task);
+
+	put_task_struct(task);
+	return ret;
+}
+
+static int proc_single_open(struct inode *inode, struct file *filp)
+{
+	return single_open(filp, proc_single_show, inode);
+}
+
+static const struct file_operations proc_single_file_operations = {
+	.open		= proc_single_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
+
+struct mm_struct *proc_mem_open(struct inode *inode, unsigned int mode)
+{
+	struct task_struct *task = get_proc_task(inode);
+	struct mm_struct *mm = ERR_PTR(-ESRCH);
+
+	if (task) {
+		mm = mm_access(task, mode | PTRACE_MODE_FSCREDS);
+		put_task_struct(task);
+
+		if (!IS_ERR_OR_NULL(mm)) {
+			/* ensure this mm_struct can't be freed */
+			mmgrab(mm);
+			/* but do not pin its memory */
+			mmput(mm);
+		}
+	}
+
+	return mm;
+}
+
+static int __mem_open(struct inode *inode, struct file *file, unsigned int mode)
+{
+	struct mm_struct *mm = proc_mem_open(inode, mode);
+
+	if (IS_ERR(mm))
+		return PTR_ERR(mm);
+
+	file->private_data = mm;
+	return 0;
+}
+
+static int mem_open(struct inode *inode, struct file *file)
+{
+	int ret = __mem_open(inode, file, PTRACE_MODE_ATTACH);
+
+	/* OK to pass negative loff_t, we can catch out-of-range */
+	file->f_mode |= FMODE_UNSIGNED_OFFSET;
+
+	return ret;
+}
+
+static ssize_t mem_rw(struct file *file, char __user *buf,
+			size_t count, loff_t *ppos, int write)
+{
+	struct mm_struct *mm = file->private_data;
+	unsigned long addr = *ppos;
+	ssize_t copied;
+	char *page;
+	unsigned int flags;
+
+	if (!mm)
+		return 0;
+
+	page = (char *)__get_free_page(GFP_KERNEL);
+	if (!page)
+		return -ENOMEM;
+
+	copied = 0;
+	if (!mmget_not_zero(mm))
+		goto free;
+
+	flags = FOLL_FORCE | (write ? FOLL_WRITE : 0);
+
+	while (count > 0) {
+		size_t this_len = min_t(size_t, count, PAGE_SIZE);
+
+		if (write && copy_from_user(page, buf, this_len)) {
+			copied = -EFAULT;
+			break;
+		}
+
+		this_len = access_remote_vm(mm, addr, page, this_len, flags);
+		if (!this_len) {
+			if (!copied)
+				copied = -EIO;
+			break;
+		}
+
+		if (!write && copy_to_user(buf, page, this_len)) {
+			copied = -EFAULT;
+			break;
+		}
+
+		buf += this_len;
+		addr += this_len;
+		copied += this_len;
+		count -= this_len;
+	}
+	*ppos = addr;
+
+	mmput(mm);
+free:
+	free_page((unsigned long) page);
+	return copied;
+}
+
+static ssize_t mem_read(struct file *file, char __user *buf,
+			size_t count, loff_t *ppos)
+{
+	return mem_rw(file, buf, count, ppos, 0);
+}
+
+static ssize_t mem_write(struct file *file, const char __user *buf,
+			 size_t count, loff_t *ppos)
+{
+	return mem_rw(file, (char __user*)buf, count, ppos, 1);
+}
+
+loff_t mem_lseek(struct file *file, loff_t offset, int orig)
+{
+	switch (orig) {
+	case 0:
+		file->f_pos = offset;
+		break;
+	case 1:
+		file->f_pos += offset;
+		break;
+	default:
+		return -EINVAL;
+	}
+	force_successful_syscall_return();
+	return file->f_pos;
+}
+
+static int mem_release(struct inode *inode, struct file *file)
+{
+	struct mm_struct *mm = file->private_data;
+	if (mm)
+		mmdrop(mm);
+	return 0;
+}
+
+static const struct file_operations proc_mem_operations = {
+	.llseek		= mem_lseek,
+	.read		= mem_read,
+	.write		= mem_write,
+	.open		= mem_open,
+	.release	= mem_release,
+};
+
+static int environ_open(struct inode *inode, struct file *file)
+{
+	return __mem_open(inode, file, PTRACE_MODE_READ);
+}
+
+static ssize_t environ_read(struct file *file, char __user *buf,
+			size_t count, loff_t *ppos)
+{
+	char *page;
+	unsigned long src = *ppos;
+	int ret = 0;
+	struct mm_struct *mm = file->private_data;
+	unsigned long env_start, env_end;
+
+	/* Ensure the process spawned far enough to have an environment. */
+	if (!mm || !mm->env_end)
+		return 0;
+
+	page = (char *)__get_free_page(GFP_KERNEL);
+	if (!page)
+		return -ENOMEM;
+
+	ret = 0;
+	if (!mmget_not_zero(mm))
+		goto free;
+
+	spin_lock(&mm->arg_lock);
+	env_start = mm->env_start;
+	env_end = mm->env_end;
+	spin_unlock(&mm->arg_lock);
+
+	while (count > 0) {
+		size_t this_len, max_len;
+		int retval;
+
+		if (src >= (env_end - env_start))
+			break;
+
+		this_len = env_end - (env_start + src);
+
+		max_len = min_t(size_t, PAGE_SIZE, count);
+		this_len = min(max_len, this_len);
+
+		retval = access_remote_vm(mm, (env_start + src), page, this_len, FOLL_ANON);
+
+		if (retval <= 0) {
+			ret = retval;
+			break;
+		}
+
+		if (copy_to_user(buf, page, retval)) {
+			ret = -EFAULT;
+			break;
+		}
+
+		ret += retval;
+		src += retval;
+		buf += retval;
+		count -= retval;
+	}
+	*ppos = src;
+	mmput(mm);
+
+free:
+	free_page((unsigned long) page);
+	return ret;
+}
+
+static const struct file_operations proc_environ_operations = {
+	.open		= environ_open,
+	.read		= environ_read,
+	.llseek		= generic_file_llseek,
+	.release	= mem_release,
+};
+
+static int auxv_open(struct inode *inode, struct file *file)
+{
+	return __mem_open(inode, file, PTRACE_MODE_READ_FSCREDS);
+}
+
+static ssize_t auxv_read(struct file *file, char __user *buf,
+			size_t count, loff_t *ppos)
+{
+	struct mm_struct *mm = file->private_data;
+	unsigned int nwords = 0;
+
+	if (!mm)
+		return 0;
+	do {
+		nwords += 2;
+	} while (mm->saved_auxv[nwords - 2] != 0); /* AT_NULL */
+	return simple_read_from_buffer(buf, count, ppos, mm->saved_auxv,
+				       nwords * sizeof(mm->saved_auxv[0]));
+}
+
+static const struct file_operations proc_auxv_operations = {
+	.open		= auxv_open,
+	.read		= auxv_read,
+	.llseek		= generic_file_llseek,
+	.release	= mem_release,
+};
+
+static ssize_t oom_adj_read(struct file *file, char __user *buf, size_t count,
+			    loff_t *ppos)
+{
+	struct task_struct *task = get_proc_task(file_inode(file));
+	char buffer[PROC_NUMBUF];
+	int oom_adj = OOM_ADJUST_MIN;
+	size_t len;
+
+	if (!task)
+		return -ESRCH;
+	if (task->signal->oom_score_adj == OOM_SCORE_ADJ_MAX)
+		oom_adj = OOM_ADJUST_MAX;
+	else
+		oom_adj = (task->signal->oom_score_adj * -OOM_DISABLE) /
+			  OOM_SCORE_ADJ_MAX;
+	put_task_struct(task);
+	if (oom_adj > OOM_ADJUST_MAX)
+		oom_adj = OOM_ADJUST_MAX;
+	len = snprintf(buffer, sizeof(buffer), "%d\n", oom_adj);
+	return simple_read_from_buffer(buf, count, ppos, buffer, len);
+}
+
+static int __set_oom_adj(struct file *file, int oom_adj, bool legacy)
+{
+	struct mm_struct *mm = NULL;
+	struct task_struct *task;
+	int err = 0;
+
+	task = get_proc_task(file_inode(file));
+	if (!task)
+		return -ESRCH;
+
+	mutex_lock(&oom_adj_mutex);
+	if (legacy) {
+		if (oom_adj < task->signal->oom_score_adj &&
+				!capable(CAP_SYS_RESOURCE)) {
+			err = -EACCES;
+			goto err_unlock;
+		}
+		/*
+		 * /proc/pid/oom_adj is provided for legacy purposes, ask users to use
+		 * /proc/pid/oom_score_adj instead.
+		 */
+		pr_warn_once("%s (%d): /proc/%d/oom_adj is deprecated, please use /proc/%d/oom_score_adj instead.\n",
+			  current->comm, task_pid_nr(current), task_pid_nr(task),
+			  task_pid_nr(task));
+	} else {
+		if ((short)oom_adj < task->signal->oom_score_adj_min &&
+				!capable(CAP_SYS_RESOURCE)) {
+			err = -EACCES;
+			goto err_unlock;
+		}
+	}
+
+	/*
+	 * Make sure we will check other processes sharing the mm if this is
+	 * not vfrok which wants its own oom_score_adj.
+	 * pin the mm so it doesn't go away and get reused after task_unlock
+	 */
+	if (!task->vfork_done) {
+		struct task_struct *p = find_lock_task_mm(task);
+
+		if (p) {
+			if (test_bit(MMF_MULTIPROCESS, &p->mm->flags)) {
+				mm = p->mm;
+				mmgrab(mm);
+			}
+			task_unlock(p);
+		}
+	}
+
+	task->signal->oom_score_adj = oom_adj;
+	if (!legacy && has_capability_noaudit(current, CAP_SYS_RESOURCE))
+		task->signal->oom_score_adj_min = (short)oom_adj;
+	trace_oom_score_adj_update(task);
+
+	if (mm) {
+		struct task_struct *p;
+
+		rcu_read_lock();
+		for_each_process(p) {
+			if (same_thread_group(task, p))
+				continue;
+
+			/* do not touch kernel threads or the global init */
+			if (p->flags & PF_KTHREAD || is_global_init(p))
+				continue;
+
+			task_lock(p);
+			if (!p->vfork_done && process_shares_mm(p, mm)) {
+				p->signal->oom_score_adj = oom_adj;
+				if (!legacy && has_capability_noaudit(current, CAP_SYS_RESOURCE))
+					p->signal->oom_score_adj_min = (short)oom_adj;
+			}
+			task_unlock(p);
+		}
+		rcu_read_unlock();
+		mmdrop(mm);
+	}
+err_unlock:
+	mutex_unlock(&oom_adj_mutex);
+	put_task_struct(task);
+	return err;
+}
+
+/*
+ * /proc/pid/oom_adj exists solely for backwards compatibility with previous
+ * kernels.  The effective policy is defined by oom_score_adj, which has a
+ * different scale: oom_adj grew exponentially and oom_score_adj grows linearly.
+ * Values written to oom_adj are simply mapped linearly to oom_score_adj.
+ * Processes that become oom disabled via oom_adj will still be oom disabled
+ * with this implementation.
+ *
+ * oom_adj cannot be removed since existing userspace binaries use it.
+ */
+static ssize_t oom_adj_write(struct file *file, const char __user *buf,
+			     size_t count, loff_t *ppos)
+{
+	char buffer[PROC_NUMBUF];
+	int oom_adj;
+	int err;
+
+	memset(buffer, 0, sizeof(buffer));
+	if (count > sizeof(buffer) - 1)
+		count = sizeof(buffer) - 1;
+	if (copy_from_user(buffer, buf, count)) {
+		err = -EFAULT;
+		goto out;
+	}
+
+	err = kstrtoint(strstrip(buffer), 0, &oom_adj);
+	if (err)
+		goto out;
+	if ((oom_adj < OOM_ADJUST_MIN || oom_adj > OOM_ADJUST_MAX) &&
+	     oom_adj != OOM_DISABLE) {
+		err = -EINVAL;
+		goto out;
+	}
+
+	/*
+	 * Scale /proc/pid/oom_score_adj appropriately ensuring that a maximum
+	 * value is always attainable.
+	 */
+	if (oom_adj == OOM_ADJUST_MAX)
+		oom_adj = OOM_SCORE_ADJ_MAX;
+	else
+		oom_adj = (oom_adj * OOM_SCORE_ADJ_MAX) / -OOM_DISABLE;
+
+	err = __set_oom_adj(file, oom_adj, true);
+out:
+	return err < 0 ? err : count;
+}
+
+static const struct file_operations proc_oom_adj_operations = {
+	.read		= oom_adj_read,
+	.write		= oom_adj_write,
+	.llseek		= generic_file_llseek,
+};
+
+static ssize_t oom_score_adj_read(struct file *file, char __user *buf,
+					size_t count, loff_t *ppos)
+{
+	struct task_struct *task = get_proc_task(file_inode(file));
+	char buffer[PROC_NUMBUF];
+	short oom_score_adj = OOM_SCORE_ADJ_MIN;
+	size_t len;
+
+	if (!task)
+		return -ESRCH;
+	oom_score_adj = task->signal->oom_score_adj;
+	put_task_struct(task);
+	len = snprintf(buffer, sizeof(buffer), "%hd\n", oom_score_adj);
+	return simple_read_from_buffer(buf, count, ppos, buffer, len);
+}
+
+static ssize_t oom_score_adj_write(struct file *file, const char __user *buf,
+					size_t count, loff_t *ppos)
+{
+	char buffer[PROC_NUMBUF];
+	int oom_score_adj;
+	int err;
+
+	memset(buffer, 0, sizeof(buffer));
+	if (count > sizeof(buffer) - 1)
+		count = sizeof(buffer) - 1;
+	if (copy_from_user(buffer, buf, count)) {
+		err = -EFAULT;
+		goto out;
+	}
+
+	err = kstrtoint(strstrip(buffer), 0, &oom_score_adj);
+	if (err)
+		goto out;
+	if (oom_score_adj < OOM_SCORE_ADJ_MIN ||
+			oom_score_adj > OOM_SCORE_ADJ_MAX) {
+		err = -EINVAL;
+		goto out;
+	}
+
+	err = __set_oom_adj(file, oom_score_adj, false);
+out:
+	return err < 0 ? err : count;
+}
+
+static const struct file_operations proc_oom_score_adj_operations = {
+	.read		= oom_score_adj_read,
+	.write		= oom_score_adj_write,
+	.llseek		= default_llseek,
+};
+
+#ifdef CONFIG_AUDIT
+#define TMPBUFLEN 11
+static ssize_t proc_loginuid_read(struct file * file, char __user * buf,
+				  size_t count, loff_t *ppos)
+{
+	struct inode * inode = file_inode(file);
+	struct task_struct *task = get_proc_task(inode);
+	ssize_t length;
+	char tmpbuf[TMPBUFLEN];
+
+	if (!task)
+		return -ESRCH;
+	length = scnprintf(tmpbuf, TMPBUFLEN, "%u",
+			   from_kuid(file->f_cred->user_ns,
+				     audit_get_loginuid(task)));
+	put_task_struct(task);
+	return simple_read_from_buffer(buf, count, ppos, tmpbuf, length);
+}
+
+static ssize_t proc_loginuid_write(struct file * file, const char __user * buf,
+				   size_t count, loff_t *ppos)
+{
+	struct inode * inode = file_inode(file);
+	uid_t loginuid;
+	kuid_t kloginuid;
+	int rv;
+
+	/* Don't let kthreads write their own loginuid */
+	if (current->flags & PF_KTHREAD)
+		return -EPERM;
+
+	rcu_read_lock();
+	if (current != pid_task(proc_pid(inode), PIDTYPE_PID)) {
+		rcu_read_unlock();
+		return -EPERM;
+	}
+	rcu_read_unlock();
+
+	if (*ppos != 0) {
+		/* No partial writes. */
+		return -EINVAL;
+	}
+
+	rv = kstrtou32_from_user(buf, count, 10, &loginuid);
+	if (rv < 0)
+		return rv;
+
+	/* is userspace tring to explicitly UNSET the loginuid? */
+	if (loginuid == AUDIT_UID_UNSET) {
+		kloginuid = INVALID_UID;
+	} else {
+		kloginuid = make_kuid(file->f_cred->user_ns, loginuid);
+		if (!uid_valid(kloginuid))
+			return -EINVAL;
+	}
+
+	rv = audit_set_loginuid(kloginuid);
+	if (rv < 0)
+		return rv;
+	return count;
+}
+
+static const struct file_operations proc_loginuid_operations = {
+	.read		= proc_loginuid_read,
+	.write		= proc_loginuid_write,
+	.llseek		= generic_file_llseek,
+};
+
+static ssize_t proc_sessionid_read(struct file * file, char __user * buf,
+				  size_t count, loff_t *ppos)
+{
+	struct inode * inode = file_inode(file);
+	struct task_struct *task = get_proc_task(inode);
+	ssize_t length;
+	char tmpbuf[TMPBUFLEN];
+
+	if (!task)
+		return -ESRCH;
+	length = scnprintf(tmpbuf, TMPBUFLEN, "%u",
+				audit_get_sessionid(task));
+	put_task_struct(task);
+	return simple_read_from_buffer(buf, count, ppos, tmpbuf, length);
+}
+
+static const struct file_operations proc_sessionid_operations = {
+	.read		= proc_sessionid_read,
+	.llseek		= generic_file_llseek,
+};
+#endif
+
+#ifdef CONFIG_FAULT_INJECTION
+static ssize_t proc_fault_inject_read(struct file * file, char __user * buf,
+				      size_t count, loff_t *ppos)
+{
+	struct task_struct *task = get_proc_task(file_inode(file));
+	char buffer[PROC_NUMBUF];
+	size_t len;
+	int make_it_fail;
+
+	if (!task)
+		return -ESRCH;
+	make_it_fail = task->make_it_fail;
+	put_task_struct(task);
+
+	len = snprintf(buffer, sizeof(buffer), "%i\n", make_it_fail);
+
+	return simple_read_from_buffer(buf, count, ppos, buffer, len);
+}
+
+static ssize_t proc_fault_inject_write(struct file * file,
+			const char __user * buf, size_t count, loff_t *ppos)
+{
+	struct task_struct *task;
+	char buffer[PROC_NUMBUF];
+	int make_it_fail;
+	int rv;
+
+	if (!capable(CAP_SYS_RESOURCE))
+		return -EPERM;
+	memset(buffer, 0, sizeof(buffer));
+	if (count > sizeof(buffer) - 1)
+		count = sizeof(buffer) - 1;
+	if (copy_from_user(buffer, buf, count))
+		return -EFAULT;
+	rv = kstrtoint(strstrip(buffer), 0, &make_it_fail);
+	if (rv < 0)
+		return rv;
+	if (make_it_fail < 0 || make_it_fail > 1)
+		return -EINVAL;
+
+	task = get_proc_task(file_inode(file));
+	if (!task)
+		return -ESRCH;
+	task->make_it_fail = make_it_fail;
+	put_task_struct(task);
+
+	return count;
+}
+
+static const struct file_operations proc_fault_inject_operations = {
+	.read		= proc_fault_inject_read,
+	.write		= proc_fault_inject_write,
+	.llseek		= generic_file_llseek,
+};
+
+static ssize_t proc_fail_nth_write(struct file *file, const char __user *buf,
+				   size_t count, loff_t *ppos)
+{
+	struct task_struct *task;
+	int err;
+	unsigned int n;
+
+	err = kstrtouint_from_user(buf, count, 0, &n);
+	if (err)
+		return err;
+
+	task = get_proc_task(file_inode(file));
+	if (!task)
+		return -ESRCH;
+	task->fail_nth = n;
+	put_task_struct(task);
+
+	return count;
+}
+
+static ssize_t proc_fail_nth_read(struct file *file, char __user *buf,
+				  size_t count, loff_t *ppos)
+{
+	struct task_struct *task;
+	char numbuf[PROC_NUMBUF];
+	ssize_t len;
+
+	task = get_proc_task(file_inode(file));
+	if (!task)
+		return -ESRCH;
+	len = snprintf(numbuf, sizeof(numbuf), "%u\n", task->fail_nth);
+	put_task_struct(task);
+	return simple_read_from_buffer(buf, count, ppos, numbuf, len);
+}
+
+static const struct file_operations proc_fail_nth_operations = {
+	.read		= proc_fail_nth_read,
+	.write		= proc_fail_nth_write,
+};
+#endif
+
+
+#ifdef CONFIG_SCHED_DEBUG
+/*
+ * Print out various scheduling related per-task fields:
+ */
+static int sched_show(struct seq_file *m, void *v)
+{
+	struct inode *inode = m->private;
+	struct pid_namespace *ns = proc_pid_ns(inode->i_sb);
+	struct task_struct *p;
+
+	p = get_proc_task(inode);
+	if (!p)
+		return -ESRCH;
+	proc_sched_show_task(p, ns, m);
+
+	put_task_struct(p);
+
+	return 0;
+}
+
+static ssize_t
+sched_write(struct file *file, const char __user *buf,
+	    size_t count, loff_t *offset)
+{
+	struct inode *inode = file_inode(file);
+	struct task_struct *p;
+
+	p = get_proc_task(inode);
+	if (!p)
+		return -ESRCH;
+	proc_sched_set_task(p);
+
+	put_task_struct(p);
+
+	return count;
+}
+
+static int sched_open(struct inode *inode, struct file *filp)
+{
+	return single_open(filp, sched_show, inode);
+}
+
+static const struct file_operations proc_pid_sched_operations = {
+	.open		= sched_open,
+	.read		= seq_read,
+	.write		= sched_write,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
+#endif
+
+#ifdef CONFIG_SCHED_AUTOGROUP
+/*
+ * Print out autogroup related information:
+ */
+static int sched_autogroup_show(struct seq_file *m, void *v)
+{
+	struct inode *inode = m->private;
+	struct task_struct *p;
+
+	p = get_proc_task(inode);
+	if (!p)
+		return -ESRCH;
+	proc_sched_autogroup_show_task(p, m);
+
+	put_task_struct(p);
+
+	return 0;
+}
+
+static ssize_t
+sched_autogroup_write(struct file *file, const char __user *buf,
+	    size_t count, loff_t *offset)
+{
+	struct inode *inode = file_inode(file);
+	struct task_struct *p;
+	char buffer[PROC_NUMBUF];
+	int nice;
+	int err;
+
+	memset(buffer, 0, sizeof(buffer));
+	if (count > sizeof(buffer) - 1)
+		count = sizeof(buffer) - 1;
+	if (copy_from_user(buffer, buf, count))
+		return -EFAULT;
+
+	err = kstrtoint(strstrip(buffer), 0, &nice);
+	if (err < 0)
+		return err;
+
+	p = get_proc_task(inode);
+	if (!p)
+		return -ESRCH;
+
+	err = proc_sched_autogroup_set_nice(p, nice);
+	if (err)
+		count = err;
+
+	put_task_struct(p);
+
+	return count;
+}
+
+static int sched_autogroup_open(struct inode *inode, struct file *filp)
+{
+	int ret;
+
+	ret = single_open(filp, sched_autogroup_show, NULL);
+	if (!ret) {
+		struct seq_file *m = filp->private_data;
+
+		m->private = inode;
+	}
+	return ret;
+}
+
+static const struct file_operations proc_pid_sched_autogroup_operations = {
+	.open		= sched_autogroup_open,
+	.read		= seq_read,
+	.write		= sched_autogroup_write,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
+#endif /* CONFIG_SCHED_AUTOGROUP */
+
+#ifdef CONFIG_TIME_NS
+static int timens_offsets_show(struct seq_file *m, void *v)
+{
+	struct task_struct *p;
+
+	p = get_proc_task(file_inode(m->file));
+	if (!p)
+		return -ESRCH;
+	proc_timens_show_offsets(p, m);
+
+	put_task_struct(p);
+
+	return 0;
+}
+
+static ssize_t timens_offsets_write(struct file *file, const char __user *buf,
+				    size_t count, loff_t *ppos)
+{
+	struct inode *inode = file_inode(file);
+	struct proc_timens_offset offsets[2];
+	char *kbuf = NULL, *pos, *next_line;
+	struct task_struct *p;
+	int ret, noffsets;
+
+	/* Only allow < page size writes at the beginning of the file */
+	if ((*ppos != 0) || (count >= PAGE_SIZE))
+		return -EINVAL;
+
+	/* Slurp in the user data */
+	kbuf = memdup_user_nul(buf, count);
+	if (IS_ERR(kbuf))
+		return PTR_ERR(kbuf);
+
+	/* Parse the user data */
+	ret = -EINVAL;
+	noffsets = 0;
+	for (pos = kbuf; pos; pos = next_line) {
+		struct proc_timens_offset *off = &offsets[noffsets];
+		char clock[10];
+		int err;
+
+		/* Find the end of line and ensure we don't look past it */
+		next_line = strchr(pos, '\n');
+		if (next_line) {
+			*next_line = '\0';
+			next_line++;
+			if (*next_line == '\0')
+				next_line = NULL;
+		}
+
+		err = sscanf(pos, "%9s %lld %lu", clock,
+				&off->val.tv_sec, &off->val.tv_nsec);
+		if (err != 3 || off->val.tv_nsec >= NSEC_PER_SEC)
+			goto out;
+
+		clock[sizeof(clock) - 1] = 0;
+		if (strcmp(clock, "monotonic") == 0 ||
+		    strcmp(clock, __stringify(CLOCK_MONOTONIC)) == 0)
+			off->clockid = CLOCK_MONOTONIC;
+		else if (strcmp(clock, "boottime") == 0 ||
+			 strcmp(clock, __stringify(CLOCK_BOOTTIME)) == 0)
+			off->clockid = CLOCK_BOOTTIME;
+		else
+			goto out;
+
+		noffsets++;
+		if (noffsets == ARRAY_SIZE(offsets)) {
+			if (next_line)
+				count = next_line - kbuf;
+			break;
+		}
+	}
+
+	ret = -ESRCH;
+	p = get_proc_task(inode);
+	if (!p)
+		goto out;
+	ret = proc_timens_set_offset(file, p, offsets, noffsets);
+	put_task_struct(p);
+	if (ret)
+		goto out;
+
+	ret = count;
+out:
+	kfree(kbuf);
+	return ret;
+}
+
+static int timens_offsets_open(struct inode *inode, struct file *filp)
+{
+	return single_open(filp, timens_offsets_show, inode);
+}
+
+static const struct file_operations proc_timens_offsets_operations = {
+	.open		= timens_offsets_open,
+	.read		= seq_read,
+	.write		= timens_offsets_write,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+#endif /* CONFIG_TIME_NS */
+
+static ssize_t comm_write(struct file *file, const char __user *buf,
+				size_t count, loff_t *offset)
+{
+	struct inode *inode = file_inode(file);
+	struct task_struct *p;
+	char buffer[TASK_COMM_LEN];
+	const size_t maxlen = sizeof(buffer) - 1;
+
+	memset(buffer, 0, sizeof(buffer));
+	if (copy_from_user(buffer, buf, count > maxlen ? maxlen : count))
+		return -EFAULT;
+
+	p = get_proc_task(inode);
+	if (!p)
+		return -ESRCH;
+
+	if (same_thread_group(current, p))
+		set_task_comm(p, buffer);
+	else
+		count = -EINVAL;
+
+	put_task_struct(p);
+
+	return count;
+}
+
+static int comm_show(struct seq_file *m, void *v)
+{
+	struct inode *inode = m->private;
+	struct task_struct *p;
+
+	p = get_proc_task(inode);
+	if (!p)
+		return -ESRCH;
+
+	proc_task_name(m, p, false);
+	seq_putc(m, '\n');
+
+	put_task_struct(p);
+
+	return 0;
+}
+
+static int comm_open(struct inode *inode, struct file *filp)
+{
+	return single_open(filp, comm_show, inode);
+}
+
+static const struct file_operations proc_pid_set_comm_operations = {
+	.open		= comm_open,
+	.read		= seq_read,
+	.write		= comm_write,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
+static int proc_exe_link(struct dentry *dentry, struct path *exe_path)
+{
+	struct task_struct *task;
+	struct file *exe_file;
+
+	task = get_proc_task(d_inode(dentry));
+	if (!task)
+		return -ENOENT;
+	exe_file = get_task_exe_file(task);
+	put_task_struct(task);
+	if (exe_file) {
+		*exe_path = exe_file->f_path;
+		path_get(&exe_file->f_path);
+		fput(exe_file);
+		return 0;
+	} else
+		return -ENOENT;
+}
+
+static const char *proc_pid_get_link(struct dentry *dentry,
+				     struct inode *inode,
+				     struct delayed_call *done)
+{
+	struct path path;
+	int error = -EACCES;
+
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+
+	/* Are we allowed to snoop on the tasks file descriptors? */
+	if (!proc_fd_access_allowed(inode))
+		goto out;
+
+	error = PROC_I(inode)->op.proc_get_link(dentry, &path);
+	if (error)
+		goto out;
+
+	error = nd_jump_link(&path);
+out:
+	return ERR_PTR(error);
+}
+
+static int do_proc_readlink(struct path *path, char __user *buffer, int buflen)
+{
+	char *tmp = (char *)__get_free_page(GFP_KERNEL);
+	char *pathname;
+	int len;
+
+	if (!tmp)
+		return -ENOMEM;
+
+	pathname = d_path(path, tmp, PAGE_SIZE);
+	len = PTR_ERR(pathname);
+	if (IS_ERR(pathname))
+		goto out;
+	len = tmp + PAGE_SIZE - 1 - pathname;
+
+	if (len > buflen)
+		len = buflen;
+	if (copy_to_user(buffer, pathname, len))
+		len = -EFAULT;
+ out:
+	free_page((unsigned long)tmp);
+	return len;
+}
+
+static int proc_pid_readlink(struct dentry * dentry, char __user * buffer, int buflen)
+{
+	int error = -EACCES;
+	struct inode *inode = d_inode(dentry);
+	struct path path;
+
+	/* Are we allowed to snoop on the tasks file descriptors? */
+	if (!proc_fd_access_allowed(inode))
+		goto out;
+
+	error = PROC_I(inode)->op.proc_get_link(dentry, &path);
+	if (error)
+		goto out;
+
+	error = do_proc_readlink(&path, buffer, buflen);
+	path_put(&path);
+out:
+	return error;
+}
+
+const struct inode_operations proc_pid_link_inode_operations = {
+	.readlink	= proc_pid_readlink,
+	.get_link	= proc_pid_get_link,
+	.setattr	= proc_setattr,
+};
+
+
+/* building an inode */
+
+void task_dump_owner(struct task_struct *task, umode_t mode,
+		     kuid_t *ruid, kgid_t *rgid)
+{
+	/* Depending on the state of dumpable compute who should own a
+	 * proc file for a task.
+	 */
+	const struct cred *cred;
+	kuid_t uid;
+	kgid_t gid;
+
+	if (unlikely(task->flags & PF_KTHREAD)) {
+		*ruid = GLOBAL_ROOT_UID;
+		*rgid = GLOBAL_ROOT_GID;
+		return;
+	}
+
+	/* Default to the tasks effective ownership */
+	rcu_read_lock();
+	cred = __task_cred(task);
+	uid = cred->euid;
+	gid = cred->egid;
+	rcu_read_unlock();
+
+	/*
+	 * Before the /proc/pid/status file was created the only way to read
+	 * the effective uid of a /process was to stat /proc/pid.  Reading
+	 * /proc/pid/status is slow enough that procps and other packages
+	 * kept stating /proc/pid.  To keep the rules in /proc simple I have
+	 * made this apply to all per process world readable and executable
+	 * directories.
+	 */
+	if (mode != (S_IFDIR|S_IRUGO|S_IXUGO)) {
+		struct mm_struct *mm;
+		task_lock(task);
+		mm = task->mm;
+		/* Make non-dumpable tasks owned by some root */
+		if (mm) {
+			if (get_dumpable(mm) != SUID_DUMP_USER) {
+				struct user_namespace *user_ns = mm->user_ns;
+
+				uid = make_kuid(user_ns, 0);
+				if (!uid_valid(uid))
+					uid = GLOBAL_ROOT_UID;
+
+				gid = make_kgid(user_ns, 0);
+				if (!gid_valid(gid))
+					gid = GLOBAL_ROOT_GID;
+			}
+		} else {
+			uid = GLOBAL_ROOT_UID;
+			gid = GLOBAL_ROOT_GID;
+		}
+		task_unlock(task);
+	}
+	*ruid = uid;
+	*rgid = gid;
+}
+
+void proc_pid_evict_inode(struct proc_inode *ei)
+{
+	struct pid *pid = ei->pid;
+
+	if (S_ISDIR(ei->vfs_inode.i_mode)) {
+		spin_lock(&pid->lock);
+		hlist_del_init_rcu(&ei->sibling_inodes);
+		spin_unlock(&pid->lock);
+	}
+
+	put_pid(pid);
+}
+
+struct inode *proc_pid_make_inode(struct super_block *sb,
+				  struct task_struct *task, umode_t mode)
+{
+	struct inode * inode;
+	struct proc_inode *ei;
+	struct pid *pid;
+
+	/* We need a new inode */
+
+	inode = new_inode(sb);
+	if (!inode)
+		goto out;
+
+	/* Common stuff */
+	ei = PROC_I(inode);
+	inode->i_mode = mode;
+	inode->i_ino = get_next_ino();
+	inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
+	inode->i_op = &proc_def_inode_operations;
+
+	/*
+	 * grab the reference to task.
+	 */
+	pid = get_task_pid(task, PIDTYPE_PID);
+	if (!pid)
+		goto out_unlock;
+
+	/* Let the pid remember us for quick removal */
+	ei->pid = pid;
+
+	task_dump_owner(task, 0, &inode->i_uid, &inode->i_gid);
+	security_task_to_inode(task, inode);
+
+out:
+	return inode;
+
+out_unlock:
+	iput(inode);
+	return NULL;
+}
+
+/*
+ * Generating an inode and adding it into @pid->inodes, so that task will
+ * invalidate inode's dentry before being released.
+ *
+ * This helper is used for creating dir-type entries under '/proc' and
+ * '/proc/<tgid>/task'. Other entries(eg. fd, stat) under '/proc/<tgid>'
+ * can be released by invalidating '/proc/<tgid>' dentry.
+ * In theory, dentries under '/proc/<tgid>/task' can also be released by
+ * invalidating '/proc/<tgid>' dentry, we reserve it to handle single
+ * thread exiting situation: Any one of threads should invalidate its
+ * '/proc/<tgid>/task/<pid>' dentry before released.
+ */
+static struct inode *proc_pid_make_base_inode(struct super_block *sb,
+				struct task_struct *task, umode_t mode)
+{
+	struct inode *inode;
+	struct proc_inode *ei;
+	struct pid *pid;
+
+	inode = proc_pid_make_inode(sb, task, mode);
+	if (!inode)
+		return NULL;
+
+	/* Let proc_flush_pid find this directory inode */
+	ei = PROC_I(inode);
+	pid = ei->pid;
+	spin_lock(&pid->lock);
+	hlist_add_head_rcu(&ei->sibling_inodes, &pid->inodes);
+	spin_unlock(&pid->lock);
+
+	return inode;
+}
+
+int pid_getattr(const struct path *path, struct kstat *stat,
+		u32 request_mask, unsigned int query_flags)
+{
+	struct inode *inode = d_inode(path->dentry);
+	struct proc_fs_info *fs_info = proc_sb_info(inode->i_sb);
+	struct task_struct *task;
+
+	generic_fillattr(inode, stat);
+
+	stat->uid = GLOBAL_ROOT_UID;
+	stat->gid = GLOBAL_ROOT_GID;
+	rcu_read_lock();
+	task = pid_task(proc_pid(inode), PIDTYPE_PID);
+	if (task) {
+		if (!has_pid_permissions(fs_info, task, HIDEPID_INVISIBLE)) {
+			rcu_read_unlock();
+			/*
+			 * This doesn't prevent learning whether PID exists,
+			 * it only makes getattr() consistent with readdir().
+			 */
+			return -ENOENT;
+		}
+		task_dump_owner(task, inode->i_mode, &stat->uid, &stat->gid);
+	}
+	rcu_read_unlock();
+	return 0;
+}
+
+/* dentry stuff */
+
+/*
+ * Set <pid>/... inode ownership (can change due to setuid(), etc.)
+ */
+void pid_update_inode(struct task_struct *task, struct inode *inode)
+{
+	task_dump_owner(task, inode->i_mode, &inode->i_uid, &inode->i_gid);
+
+	inode->i_mode &= ~(S_ISUID | S_ISGID);
+	security_task_to_inode(task, inode);
+}
+
+/*
+ * Rewrite the inode's ownerships here because the owning task may have
+ * performed a setuid(), etc.
+ *
+ */
+static int pid_revalidate(struct dentry *dentry, unsigned int flags)
+{
+	struct inode *inode;
+	struct task_struct *task;
+
+	if (flags & LOOKUP_RCU)
+		return -ECHILD;
+
+	inode = d_inode(dentry);
+	task = get_proc_task(inode);
+
+	if (task) {
+		pid_update_inode(task, inode);
+		put_task_struct(task);
+		return 1;
+	}
+	return 0;
+}
+
+static inline bool proc_inode_is_dead(struct inode *inode)
+{
+	return !proc_pid(inode)->tasks[PIDTYPE_PID].first;
+}
+
+int pid_delete_dentry(const struct dentry *dentry)
+{
+	/* Is the task we represent dead?
+	 * If so, then don't put the dentry on the lru list,
+	 * kill it immediately.
+	 */
+	return proc_inode_is_dead(d_inode(dentry));
+}
+
+const struct dentry_operations pid_dentry_operations =
+{
+	.d_revalidate	= pid_revalidate,
+	.d_delete	= pid_delete_dentry,
+};
+
+/* Lookups */
+
+/*
+ * Fill a directory entry.
+ *
+ * If possible create the dcache entry and derive our inode number and
+ * file type from dcache entry.
+ *
+ * Since all of the proc inode numbers are dynamically generated, the inode
+ * numbers do not exist until the inode is cache.  This means creating the
+ * the dcache entry in readdir is necessary to keep the inode numbers
+ * reported by readdir in sync with the inode numbers reported
+ * by stat.
+ */
+bool proc_fill_cache(struct file *file, struct dir_context *ctx,
+	const char *name, unsigned int len,
+	instantiate_t instantiate, struct task_struct *task, const void *ptr)
+{
+	struct dentry *child, *dir = file->f_path.dentry;
+	struct qstr qname = QSTR_INIT(name, len);
+	struct inode *inode;
+	unsigned type = DT_UNKNOWN;
+	ino_t ino = 1;
+
+	child = d_hash_and_lookup(dir, &qname);
+	if (!child) {
+		DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
+		child = d_alloc_parallel(dir, &qname, &wq);
+		if (IS_ERR(child))
+			goto end_instantiate;
+		if (d_in_lookup(child)) {
+			struct dentry *res;
+			res = instantiate(child, task, ptr);
+			d_lookup_done(child);
+			if (unlikely(res)) {
+				dput(child);
+				child = res;
+				if (IS_ERR(child))
+					goto end_instantiate;
+			}
+		}
+	}
+	inode = d_inode(child);
+	ino = inode->i_ino;
+	type = inode->i_mode >> 12;
+	dput(child);
+end_instantiate:
+	return dir_emit(ctx, name, len, ino, type);
+}
+
+/*
+ * dname_to_vma_addr - maps a dentry name into two unsigned longs
+ * which represent vma start and end addresses.
+ */
+static int dname_to_vma_addr(struct dentry *dentry,
+			     unsigned long *start, unsigned long *end)
+{
+	const char *str = dentry->d_name.name;
+	unsigned long long sval, eval;
+	unsigned int len;
+
+	if (str[0] == '0' && str[1] != '-')
+		return -EINVAL;
+	len = _parse_integer(str, 16, &sval);
+	if (len & KSTRTOX_OVERFLOW)
+		return -EINVAL;
+	if (sval != (unsigned long)sval)
+		return -EINVAL;
+	str += len;
+
+	if (*str != '-')
+		return -EINVAL;
+	str++;
+
+	if (str[0] == '0' && str[1])
+		return -EINVAL;
+	len = _parse_integer(str, 16, &eval);
+	if (len & KSTRTOX_OVERFLOW)
+		return -EINVAL;
+	if (eval != (unsigned long)eval)
+		return -EINVAL;
+	str += len;
+
+	if (*str != '\0')
+		return -EINVAL;
+
+	*start = sval;
+	*end = eval;
+
+	return 0;
+}
+
+static int map_files_d_revalidate(struct dentry *dentry, unsigned int flags)
+{
+	unsigned long vm_start, vm_end;
+	bool exact_vma_exists = false;
+	struct mm_struct *mm = NULL;
+	struct task_struct *task;
+	struct inode *inode;
+	int status = 0;
+
+	if (flags & LOOKUP_RCU)
+		return -ECHILD;
+
+	inode = d_inode(dentry);
+	task = get_proc_task(inode);
+	if (!task)
+		goto out_notask;
+
+	mm = mm_access(task, PTRACE_MODE_READ_FSCREDS);
+	if (IS_ERR_OR_NULL(mm))
+		goto out;
+
+	if (!dname_to_vma_addr(dentry, &vm_start, &vm_end)) {
+		status = mmap_read_lock_killable(mm);
+		if (!status) {
+			exact_vma_exists = !!find_exact_vma(mm, vm_start,
+							    vm_end);
+			mmap_read_unlock(mm);
+		}
+	}
+
+	mmput(mm);
+
+	if (exact_vma_exists) {
+		task_dump_owner(task, 0, &inode->i_uid, &inode->i_gid);
+
+		security_task_to_inode(task, inode);
+		status = 1;
+	}
+
+out:
+	put_task_struct(task);
+
+out_notask:
+	return status;
+}
+
+static const struct dentry_operations tid_map_files_dentry_operations = {
+	.d_revalidate	= map_files_d_revalidate,
+	.d_delete	= pid_delete_dentry,
+};
+
+static int map_files_get_link(struct dentry *dentry, struct path *path)
+{
+	unsigned long vm_start, vm_end;
+	struct vm_area_struct *vma;
+	struct task_struct *task;
+	struct mm_struct *mm;
+	int rc;
+
+	rc = -ENOENT;
+	task = get_proc_task(d_inode(dentry));
+	if (!task)
+		goto out;
+
+	mm = get_task_mm(task);
+	put_task_struct(task);
+	if (!mm)
+		goto out;
+
+	rc = dname_to_vma_addr(dentry, &vm_start, &vm_end);
+	if (rc)
+		goto out_mmput;
+
+	rc = mmap_read_lock_killable(mm);
+	if (rc)
+		goto out_mmput;
+
+	rc = -ENOENT;
+	vma = find_exact_vma(mm, vm_start, vm_end);
+	if (vma && vma->vm_file) {
+		*path = vma->vm_file->f_path;
+		path_get(path);
+		rc = 0;
+	}
+	mmap_read_unlock(mm);
+
+out_mmput:
+	mmput(mm);
+out:
+	return rc;
+}
+
+struct map_files_info {
+	unsigned long	start;
+	unsigned long	end;
+	fmode_t		mode;
+};
+
+/*
+ * Only allow CAP_SYS_ADMIN and CAP_CHECKPOINT_RESTORE to follow the links, due
+ * to concerns about how the symlinks may be used to bypass permissions on
+ * ancestor directories in the path to the file in question.
+ */
+static const char *
+proc_map_files_get_link(struct dentry *dentry,
+			struct inode *inode,
+		        struct delayed_call *done)
+{
+	if (!checkpoint_restore_ns_capable(&init_user_ns))
+		return ERR_PTR(-EPERM);
+
+	return proc_pid_get_link(dentry, inode, done);
+}
+
+/*
+ * Identical to proc_pid_link_inode_operations except for get_link()
+ */
+static const struct inode_operations proc_map_files_link_inode_operations = {
+	.readlink	= proc_pid_readlink,
+	.get_link	= proc_map_files_get_link,
+	.setattr	= proc_setattr,
+};
+
+static struct dentry *
+proc_map_files_instantiate(struct dentry *dentry,
+			   struct task_struct *task, const void *ptr)
+{
+	fmode_t mode = (fmode_t)(unsigned long)ptr;
+	struct proc_inode *ei;
+	struct inode *inode;
+
+	inode = proc_pid_make_inode(dentry->d_sb, task, S_IFLNK |
+				    ((mode & FMODE_READ ) ? S_IRUSR : 0) |
+				    ((mode & FMODE_WRITE) ? S_IWUSR : 0));
+	if (!inode)
+		return ERR_PTR(-ENOENT);
+
+	ei = PROC_I(inode);
+	ei->op.proc_get_link = map_files_get_link;
+
+	inode->i_op = &proc_map_files_link_inode_operations;
+	inode->i_size = 64;
+
+	d_set_d_op(dentry, &tid_map_files_dentry_operations);
+	return d_splice_alias(inode, dentry);
+}
+
+static struct dentry *proc_map_files_lookup(struct inode *dir,
+		struct dentry *dentry, unsigned int flags)
+{
+	unsigned long vm_start, vm_end;
+	struct vm_area_struct *vma;
+	struct task_struct *task;
+	struct dentry *result;
+	struct mm_struct *mm;
+
+	result = ERR_PTR(-ENOENT);
+	task = get_proc_task(dir);
+	if (!task)
+		goto out;
+
+	result = ERR_PTR(-EACCES);
+	if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
+		goto out_put_task;
+
+	result = ERR_PTR(-ENOENT);
+	if (dname_to_vma_addr(dentry, &vm_start, &vm_end))
+		goto out_put_task;
+
+	mm = get_task_mm(task);
+	if (!mm)
+		goto out_put_task;
+
+	result = ERR_PTR(-EINTR);
+	if (mmap_read_lock_killable(mm))
+		goto out_put_mm;
+
+	result = ERR_PTR(-ENOENT);
+	vma = find_exact_vma(mm, vm_start, vm_end);
+	if (!vma)
+		goto out_no_vma;
+
+	if (vma->vm_file)
+		result = proc_map_files_instantiate(dentry, task,
+				(void *)(unsigned long)vma->vm_file->f_mode);
+
+out_no_vma:
+	mmap_read_unlock(mm);
+out_put_mm:
+	mmput(mm);
+out_put_task:
+	put_task_struct(task);
+out:
+	return result;
+}
+
+static const struct inode_operations proc_map_files_inode_operations = {
+	.lookup		= proc_map_files_lookup,
+	.permission	= proc_fd_permission,
+	.setattr	= proc_setattr,
+};
+
+static int
+proc_map_files_readdir(struct file *file, struct dir_context *ctx)
+{
+	struct vm_area_struct *vma;
+	struct task_struct *task;
+	struct mm_struct *mm;
+	unsigned long nr_files, pos, i;
+	GENRADIX(struct map_files_info) fa;
+	struct map_files_info *p;
+	int ret;
+
+	genradix_init(&fa);
+
+	ret = -ENOENT;
+	task = get_proc_task(file_inode(file));
+	if (!task)
+		goto out;
+
+	ret = -EACCES;
+	if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
+		goto out_put_task;
+
+	ret = 0;
+	if (!dir_emit_dots(file, ctx))
+		goto out_put_task;
+
+	mm = get_task_mm(task);
+	if (!mm)
+		goto out_put_task;
+
+	ret = mmap_read_lock_killable(mm);
+	if (ret) {
+		mmput(mm);
+		goto out_put_task;
+	}
+
+	nr_files = 0;
+
+	/*
+	 * We need two passes here:
+	 *
+	 *  1) Collect vmas of mapped files with mmap_lock taken
+	 *  2) Release mmap_lock and instantiate entries
+	 *
+	 * otherwise we get lockdep complained, since filldir()
+	 * routine might require mmap_lock taken in might_fault().
+	 */
+
+	for (vma = mm->mmap, pos = 2; vma; vma = vma->vm_next) {
+		if (!vma->vm_file)
+			continue;
+		if (++pos <= ctx->pos)
+			continue;
+
+		p = genradix_ptr_alloc(&fa, nr_files++, GFP_KERNEL);
+		if (!p) {
+			ret = -ENOMEM;
+			mmap_read_unlock(mm);
+			mmput(mm);
+			goto out_put_task;
+		}
+
+		p->start = vma->vm_start;
+		p->end = vma->vm_end;
+		p->mode = vma->vm_file->f_mode;
+	}
+	mmap_read_unlock(mm);
+	mmput(mm);
+
+	for (i = 0; i < nr_files; i++) {
+		char buf[4 * sizeof(long) + 2];	/* max: %lx-%lx\0 */
+		unsigned int len;
+
+		p = genradix_ptr(&fa, i);
+		len = snprintf(buf, sizeof(buf), "%lx-%lx", p->start, p->end);
+		if (!proc_fill_cache(file, ctx,
+				      buf, len,
+				      proc_map_files_instantiate,
+				      task,
+				      (void *)(unsigned long)p->mode))
+			break;
+		ctx->pos++;
+	}
+
+out_put_task:
+	put_task_struct(task);
+out:
+	genradix_free(&fa);
+	return ret;
+}
+
+static const struct file_operations proc_map_files_operations = {
+	.read		= generic_read_dir,
+	.iterate_shared	= proc_map_files_readdir,
+	.llseek		= generic_file_llseek,
+};
+
+#if defined(CONFIG_CHECKPOINT_RESTORE) && defined(CONFIG_POSIX_TIMERS)
+struct timers_private {
+	struct pid *pid;
+	struct task_struct *task;
+	struct sighand_struct *sighand;
+	struct pid_namespace *ns;
+	unsigned long flags;
+};
+
+static void *timers_start(struct seq_file *m, loff_t *pos)
+{
+	struct timers_private *tp = m->private;
+
+	tp->task = get_pid_task(tp->pid, PIDTYPE_PID);
+	if (!tp->task)
+		return ERR_PTR(-ESRCH);
+
+	tp->sighand = lock_task_sighand(tp->task, &tp->flags);
+	if (!tp->sighand)
+		return ERR_PTR(-ESRCH);
+
+	return seq_list_start(&tp->task->signal->posix_timers, *pos);
+}
+
+static void *timers_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	struct timers_private *tp = m->private;
+	return seq_list_next(v, &tp->task->signal->posix_timers, pos);
+}
+
+static void timers_stop(struct seq_file *m, void *v)
+{
+	struct timers_private *tp = m->private;
+
+	if (tp->sighand) {
+		unlock_task_sighand(tp->task, &tp->flags);
+		tp->sighand = NULL;
+	}
+
+	if (tp->task) {
+		put_task_struct(tp->task);
+		tp->task = NULL;
+	}
+}
+
+static int show_timer(struct seq_file *m, void *v)
+{
+	struct k_itimer *timer;
+	struct timers_private *tp = m->private;
+	int notify;
+	static const char * const nstr[] = {
+		[SIGEV_SIGNAL] = "signal",
+		[SIGEV_NONE] = "none",
+		[SIGEV_THREAD] = "thread",
+	};
+
+	timer = list_entry((struct list_head *)v, struct k_itimer, list);
+	notify = timer->it_sigev_notify;
+
+	seq_printf(m, "ID: %d\n", timer->it_id);
+	seq_printf(m, "signal: %d/%px\n",
+		   timer->sigq->info.si_signo,
+		   timer->sigq->info.si_value.sival_ptr);
+	seq_printf(m, "notify: %s/%s.%d\n",
+		   nstr[notify & ~SIGEV_THREAD_ID],
+		   (notify & SIGEV_THREAD_ID) ? "tid" : "pid",
+		   pid_nr_ns(timer->it_pid, tp->ns));
+	seq_printf(m, "ClockID: %d\n", timer->it_clock);
+
+	return 0;
+}
+
+static const struct seq_operations proc_timers_seq_ops = {
+	.start	= timers_start,
+	.next	= timers_next,
+	.stop	= timers_stop,
+	.show	= show_timer,
+};
+
+static int proc_timers_open(struct inode *inode, struct file *file)
+{
+	struct timers_private *tp;
+
+	tp = __seq_open_private(file, &proc_timers_seq_ops,
+			sizeof(struct timers_private));
+	if (!tp)
+		return -ENOMEM;
+
+	tp->pid = proc_pid(inode);
+	tp->ns = proc_pid_ns(inode->i_sb);
+	return 0;
+}
+
+static const struct file_operations proc_timers_operations = {
+	.open		= proc_timers_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= seq_release_private,
+};
+#endif
+
+static ssize_t timerslack_ns_write(struct file *file, const char __user *buf,
+					size_t count, loff_t *offset)
+{
+	struct inode *inode = file_inode(file);
+	struct task_struct *p;
+	u64 slack_ns;
+	int err;
+
+	err = kstrtoull_from_user(buf, count, 10, &slack_ns);
+	if (err < 0)
+		return err;
+
+	p = get_proc_task(inode);
+	if (!p)
+		return -ESRCH;
+
+	if (p != current) {
+		rcu_read_lock();
+		if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) {
+			rcu_read_unlock();
+			count = -EPERM;
+			goto out;
+		}
+		rcu_read_unlock();
+
+		err = security_task_setscheduler(p);
+		if (err) {
+			count = err;
+			goto out;
+		}
+	}
+
+	task_lock(p);
+	if (slack_ns == 0)
+		p->timer_slack_ns = p->default_timer_slack_ns;
+	else
+		p->timer_slack_ns = slack_ns;
+	task_unlock(p);
+
+out:
+	put_task_struct(p);
+
+	return count;
+}
+
+static int timerslack_ns_show(struct seq_file *m, void *v)
+{
+	struct inode *inode = m->private;
+	struct task_struct *p;
+	int err = 0;
+
+	p = get_proc_task(inode);
+	if (!p)
+		return -ESRCH;
+
+	if (p != current) {
+		rcu_read_lock();
+		if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) {
+			rcu_read_unlock();
+			err = -EPERM;
+			goto out;
+		}
+		rcu_read_unlock();
+
+		err = security_task_getscheduler(p);
+		if (err)
+			goto out;
+	}
+
+	task_lock(p);
+	seq_printf(m, "%llu\n", p->timer_slack_ns);
+	task_unlock(p);
+
+out:
+	put_task_struct(p);
+
+	return err;
+}
+
+static int timerslack_ns_open(struct inode *inode, struct file *filp)
+{
+	return single_open(filp, timerslack_ns_show, inode);
+}
+
+static const struct file_operations proc_pid_set_timerslack_ns_operations = {
+	.open		= timerslack_ns_open,
+	.read		= seq_read,
+	.write		= timerslack_ns_write,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
+static struct dentry *proc_pident_instantiate(struct dentry *dentry,
+	struct task_struct *task, const void *ptr)
+{
+	const struct pid_entry *p = ptr;
+	struct inode *inode;
+	struct proc_inode *ei;
+
+	inode = proc_pid_make_inode(dentry->d_sb, task, p->mode);
+	if (!inode)
+		return ERR_PTR(-ENOENT);
+
+	ei = PROC_I(inode);
+	if (S_ISDIR(inode->i_mode))
+		set_nlink(inode, 2);	/* Use getattr to fix if necessary */
+	if (p->iop)
+		inode->i_op = p->iop;
+	if (p->fop)
+		inode->i_fop = p->fop;
+	ei->op = p->op;
+	pid_update_inode(task, inode);
+	d_set_d_op(dentry, &pid_dentry_operations);
+	return d_splice_alias(inode, dentry);
+}
+
+static struct dentry *proc_pident_lookup(struct inode *dir, 
+					 struct dentry *dentry,
+					 const struct pid_entry *p,
+					 const struct pid_entry *end)
+{
+	struct task_struct *task = get_proc_task(dir);
+	struct dentry *res = ERR_PTR(-ENOENT);
+
+	if (!task)
+		goto out_no_task;
+
+	/*
+	 * Yes, it does not scale. And it should not. Don't add
+	 * new entries into /proc/<tgid>/ without very good reasons.
+	 */
+	for (; p < end; p++) {
+		if (p->len != dentry->d_name.len)
+			continue;
+		if (!memcmp(dentry->d_name.name, p->name, p->len)) {
+			res = proc_pident_instantiate(dentry, task, p);
+			break;
+		}
+	}
+	put_task_struct(task);
+out_no_task:
+	return res;
+}
+
+static int proc_pident_readdir(struct file *file, struct dir_context *ctx,
+		const struct pid_entry *ents, unsigned int nents)
+{
+	struct task_struct *task = get_proc_task(file_inode(file));
+	const struct pid_entry *p;
+
+	if (!task)
+		return -ENOENT;
+
+	if (!dir_emit_dots(file, ctx))
+		goto out;
+
+	if (ctx->pos >= nents + 2)
+		goto out;
+
+	for (p = ents + (ctx->pos - 2); p < ents + nents; p++) {
+		if (!proc_fill_cache(file, ctx, p->name, p->len,
+				proc_pident_instantiate, task, p))
+			break;
+		ctx->pos++;
+	}
+out:
+	put_task_struct(task);
+	return 0;
+}
+
+#ifdef CONFIG_SECURITY
+static int proc_pid_attr_open(struct inode *inode, struct file *file)
+{
+	file->private_data = NULL;
+	__mem_open(inode, file, PTRACE_MODE_READ_FSCREDS);
+	return 0;
+}
+
+static ssize_t proc_pid_attr_read(struct file * file, char __user * buf,
+				  size_t count, loff_t *ppos)
+{
+	struct inode * inode = file_inode(file);
+	char *p = NULL;
+	ssize_t length;
+	struct task_struct *task = get_proc_task(inode);
+
+	if (!task)
+		return -ESRCH;
+
+	length = security_getprocattr(task, PROC_I(inode)->op.lsm,
+				      (char*)file->f_path.dentry->d_name.name,
+				      &p);
+	put_task_struct(task);
+	if (length > 0)
+		length = simple_read_from_buffer(buf, count, ppos, p, length);
+	kfree(p);
+	return length;
+}
+
+static ssize_t proc_pid_attr_write(struct file * file, const char __user * buf,
+				   size_t count, loff_t *ppos)
+{
+	struct inode * inode = file_inode(file);
+	struct task_struct *task;
+	void *page;
+	int rv;
+
+	/* A task may only write when it was the opener. */
+	if (file->private_data != current->mm)
+		return -EPERM;
+
+	rcu_read_lock();
+	task = pid_task(proc_pid(inode), PIDTYPE_PID);
+	if (!task) {
+		rcu_read_unlock();
+		return -ESRCH;
+	}
+	/* A task may only write its own attributes. */
+	if (current != task) {
+		rcu_read_unlock();
+		return -EACCES;
+	}
+	/* Prevent changes to overridden credentials. */
+	if (current_cred() != current_real_cred()) {
+		rcu_read_unlock();
+		return -EBUSY;
+	}
+	rcu_read_unlock();
+
+	if (count > PAGE_SIZE)
+		count = PAGE_SIZE;
+
+	/* No partial writes. */
+	if (*ppos != 0)
+		return -EINVAL;
+
+	page = memdup_user(buf, count);
+	if (IS_ERR(page)) {
+		rv = PTR_ERR(page);
+		goto out;
+	}
+
+	/* Guard against adverse ptrace interaction */
+	rv = mutex_lock_interruptible(&current->signal->cred_guard_mutex);
+	if (rv < 0)
+		goto out_free;
+
+	rv = security_setprocattr(PROC_I(inode)->op.lsm,
+				  file->f_path.dentry->d_name.name, page,
+				  count);
+	mutex_unlock(&current->signal->cred_guard_mutex);
+out_free:
+	kfree(page);
+out:
+	return rv;
+}
+
+static const struct file_operations proc_pid_attr_operations = {
+	.open		= proc_pid_attr_open,
+	.read		= proc_pid_attr_read,
+	.write		= proc_pid_attr_write,
+	.llseek		= generic_file_llseek,
+	.release	= mem_release,
+};
+
+#define LSM_DIR_OPS(LSM) \
+static int proc_##LSM##_attr_dir_iterate(struct file *filp, \
+			     struct dir_context *ctx) \
+{ \
+	return proc_pident_readdir(filp, ctx, \
+				   LSM##_attr_dir_stuff, \
+				   ARRAY_SIZE(LSM##_attr_dir_stuff)); \
+} \
+\
+static const struct file_operations proc_##LSM##_attr_dir_ops = { \
+	.read		= generic_read_dir, \
+	.iterate	= proc_##LSM##_attr_dir_iterate, \
+	.llseek		= default_llseek, \
+}; \
+\
+static struct dentry *proc_##LSM##_attr_dir_lookup(struct inode *dir, \
+				struct dentry *dentry, unsigned int flags) \
+{ \
+	return proc_pident_lookup(dir, dentry, \
+				  LSM##_attr_dir_stuff, \
+				  LSM##_attr_dir_stuff + ARRAY_SIZE(LSM##_attr_dir_stuff)); \
+} \
+\
+static const struct inode_operations proc_##LSM##_attr_dir_inode_ops = { \
+	.lookup		= proc_##LSM##_attr_dir_lookup, \
+	.getattr	= pid_getattr, \
+	.setattr	= proc_setattr, \
+}
+
+#ifdef CONFIG_SECURITY_SMACK
+static const struct pid_entry smack_attr_dir_stuff[] = {
+	ATTR("smack", "current",	0666),
+};
+LSM_DIR_OPS(smack);
+#endif
+
+#ifdef CONFIG_SECURITY_APPARMOR
+static const struct pid_entry apparmor_attr_dir_stuff[] = {
+	ATTR("apparmor", "current",	0666),
+	ATTR("apparmor", "prev",	0444),
+	ATTR("apparmor", "exec",	0666),
+};
+LSM_DIR_OPS(apparmor);
+#endif
+
+static const struct pid_entry attr_dir_stuff[] = {
+	ATTR(NULL, "current",		0666),
+	ATTR(NULL, "prev",		0444),
+	ATTR(NULL, "exec",		0666),
+	ATTR(NULL, "fscreate",		0666),
+	ATTR(NULL, "keycreate",		0666),
+	ATTR(NULL, "sockcreate",	0666),
+#ifdef CONFIG_SECURITY_SMACK
+	DIR("smack",			0555,
+	    proc_smack_attr_dir_inode_ops, proc_smack_attr_dir_ops),
+#endif
+#ifdef CONFIG_SECURITY_APPARMOR
+	DIR("apparmor",			0555,
+	    proc_apparmor_attr_dir_inode_ops, proc_apparmor_attr_dir_ops),
+#endif
+};
+
+static int proc_attr_dir_readdir(struct file *file, struct dir_context *ctx)
+{
+	return proc_pident_readdir(file, ctx, 
+				   attr_dir_stuff, ARRAY_SIZE(attr_dir_stuff));
+}
+
+static const struct file_operations proc_attr_dir_operations = {
+	.read		= generic_read_dir,
+	.iterate_shared	= proc_attr_dir_readdir,
+	.llseek		= generic_file_llseek,
+};
+
+static struct dentry *proc_attr_dir_lookup(struct inode *dir,
+				struct dentry *dentry, unsigned int flags)
+{
+	return proc_pident_lookup(dir, dentry,
+				  attr_dir_stuff,
+				  attr_dir_stuff + ARRAY_SIZE(attr_dir_stuff));
+}
+
+static const struct inode_operations proc_attr_dir_inode_operations = {
+	.lookup		= proc_attr_dir_lookup,
+	.getattr	= pid_getattr,
+	.setattr	= proc_setattr,
+};
+
+#endif
+
+#ifdef CONFIG_ELF_CORE
+static ssize_t proc_coredump_filter_read(struct file *file, char __user *buf,
+					 size_t count, loff_t *ppos)
+{
+	struct task_struct *task = get_proc_task(file_inode(file));
+	struct mm_struct *mm;
+	char buffer[PROC_NUMBUF];
+	size_t len;
+	int ret;
+
+	if (!task)
+		return -ESRCH;
+
+	ret = 0;
+	mm = get_task_mm(task);
+	if (mm) {
+		len = snprintf(buffer, sizeof(buffer), "%08lx\n",
+			       ((mm->flags & MMF_DUMP_FILTER_MASK) >>
+				MMF_DUMP_FILTER_SHIFT));
+		mmput(mm);
+		ret = simple_read_from_buffer(buf, count, ppos, buffer, len);
+	}
+
+	put_task_struct(task);
+
+	return ret;
+}
+
+static ssize_t proc_coredump_filter_write(struct file *file,
+					  const char __user *buf,
+					  size_t count,
+					  loff_t *ppos)
+{
+	struct task_struct *task;
+	struct mm_struct *mm;
+	unsigned int val;
+	int ret;
+	int i;
+	unsigned long mask;
+
+	ret = kstrtouint_from_user(buf, count, 0, &val);
+	if (ret < 0)
+		return ret;
+
+	ret = -ESRCH;
+	task = get_proc_task(file_inode(file));
+	if (!task)
+		goto out_no_task;
+
+	mm = get_task_mm(task);
+	if (!mm)
+		goto out_no_mm;
+	ret = 0;
+
+	for (i = 0, mask = 1; i < MMF_DUMP_FILTER_BITS; i++, mask <<= 1) {
+		if (val & mask)
+			set_bit(i + MMF_DUMP_FILTER_SHIFT, &mm->flags);
+		else
+			clear_bit(i + MMF_DUMP_FILTER_SHIFT, &mm->flags);
+	}
+
+	mmput(mm);
+ out_no_mm:
+	put_task_struct(task);
+ out_no_task:
+	if (ret < 0)
+		return ret;
+	return count;
+}
+
+static const struct file_operations proc_coredump_filter_operations = {
+	.read		= proc_coredump_filter_read,
+	.write		= proc_coredump_filter_write,
+	.llseek		= generic_file_llseek,
+};
+#endif
+
+#ifdef CONFIG_TASK_IO_ACCOUNTING
+static int do_io_accounting(struct task_struct *task, struct seq_file *m, int whole)
+{
+	struct task_io_accounting acct = task->ioac;
+	unsigned long flags;
+	int result;
+
+	result = down_read_killable(&task->signal->exec_update_lock);
+	if (result)
+		return result;
+
+	if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS)) {
+		result = -EACCES;
+		goto out_unlock;
+	}
+
+	if (whole && lock_task_sighand(task, &flags)) {
+		struct task_struct *t = task;
+
+		task_io_accounting_add(&acct, &task->signal->ioac);
+		while_each_thread(task, t)
+			task_io_accounting_add(&acct, &t->ioac);
+
+		unlock_task_sighand(task, &flags);
+	}
+	seq_printf(m,
+		   "rchar: %llu\n"
+		   "wchar: %llu\n"
+		   "syscr: %llu\n"
+		   "syscw: %llu\n"
+		   "read_bytes: %llu\n"
+		   "write_bytes: %llu\n"
+		   "cancelled_write_bytes: %llu\n",
+		   (unsigned long long)acct.rchar,
+		   (unsigned long long)acct.wchar,
+		   (unsigned long long)acct.syscr,
+		   (unsigned long long)acct.syscw,
+		   (unsigned long long)acct.read_bytes,
+		   (unsigned long long)acct.write_bytes,
+		   (unsigned long long)acct.cancelled_write_bytes);
+	result = 0;
+
+out_unlock:
+	up_read(&task->signal->exec_update_lock);
+	return result;
+}
+
+static int proc_tid_io_accounting(struct seq_file *m, struct pid_namespace *ns,
+				  struct pid *pid, struct task_struct *task)
+{
+	return do_io_accounting(task, m, 0);
+}
+
+static int proc_tgid_io_accounting(struct seq_file *m, struct pid_namespace *ns,
+				   struct pid *pid, struct task_struct *task)
+{
+	return do_io_accounting(task, m, 1);
+}
+#endif /* CONFIG_TASK_IO_ACCOUNTING */
+
+#ifdef CONFIG_USER_NS
+static int proc_id_map_open(struct inode *inode, struct file *file,
+	const struct seq_operations *seq_ops)
+{
+	struct user_namespace *ns = NULL;
+	struct task_struct *task;
+	struct seq_file *seq;
+	int ret = -EINVAL;
+
+	task = get_proc_task(inode);
+	if (task) {
+		rcu_read_lock();
+		ns = get_user_ns(task_cred_xxx(task, user_ns));
+		rcu_read_unlock();
+		put_task_struct(task);
+	}
+	if (!ns)
+		goto err;
+
+	ret = seq_open(file, seq_ops);
+	if (ret)
+		goto err_put_ns;
+
+	seq = file->private_data;
+	seq->private = ns;
+
+	return 0;
+err_put_ns:
+	put_user_ns(ns);
+err:
+	return ret;
+}
+
+static int proc_id_map_release(struct inode *inode, struct file *file)
+{
+	struct seq_file *seq = file->private_data;
+	struct user_namespace *ns = seq->private;
+	put_user_ns(ns);
+	return seq_release(inode, file);
+}
+
+static int proc_uid_map_open(struct inode *inode, struct file *file)
+{
+	return proc_id_map_open(inode, file, &proc_uid_seq_operations);
+}
+
+static int proc_gid_map_open(struct inode *inode, struct file *file)
+{
+	return proc_id_map_open(inode, file, &proc_gid_seq_operations);
+}
+
+static int proc_projid_map_open(struct inode *inode, struct file *file)
+{
+	return proc_id_map_open(inode, file, &proc_projid_seq_operations);
+}
+
+static const struct file_operations proc_uid_map_operations = {
+	.open		= proc_uid_map_open,
+	.write		= proc_uid_map_write,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= proc_id_map_release,
+};
+
+static const struct file_operations proc_gid_map_operations = {
+	.open		= proc_gid_map_open,
+	.write		= proc_gid_map_write,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= proc_id_map_release,
+};
+
+static const struct file_operations proc_projid_map_operations = {
+	.open		= proc_projid_map_open,
+	.write		= proc_projid_map_write,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= proc_id_map_release,
+};
+
+static int proc_setgroups_open(struct inode *inode, struct file *file)
+{
+	struct user_namespace *ns = NULL;
+	struct task_struct *task;
+	int ret;
+
+	ret = -ESRCH;
+	task = get_proc_task(inode);
+	if (task) {
+		rcu_read_lock();
+		ns = get_user_ns(task_cred_xxx(task, user_ns));
+		rcu_read_unlock();
+		put_task_struct(task);
+	}
+	if (!ns)
+		goto err;
+
+	if (file->f_mode & FMODE_WRITE) {
+		ret = -EACCES;
+		if (!ns_capable(ns, CAP_SYS_ADMIN))
+			goto err_put_ns;
+	}
+
+	ret = single_open(file, &proc_setgroups_show, ns);
+	if (ret)
+		goto err_put_ns;
+
+	return 0;
+err_put_ns:
+	put_user_ns(ns);
+err:
+	return ret;
+}
+
+static int proc_setgroups_release(struct inode *inode, struct file *file)
+{
+	struct seq_file *seq = file->private_data;
+	struct user_namespace *ns = seq->private;
+	int ret = single_release(inode, file);
+	put_user_ns(ns);
+	return ret;
+}
+
+static const struct file_operations proc_setgroups_operations = {
+	.open		= proc_setgroups_open,
+	.write		= proc_setgroups_write,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= proc_setgroups_release,
+};
+#endif /* CONFIG_USER_NS */
+
+static int proc_pid_personality(struct seq_file *m, struct pid_namespace *ns,
+				struct pid *pid, struct task_struct *task)
+{
+	int err = lock_trace(task);
+	if (!err) {
+		seq_printf(m, "%08x\n", task->personality);
+		unlock_trace(task);
+	}
+	return err;
+}
+
+#ifdef CONFIG_LIVEPATCH
+static int proc_pid_patch_state(struct seq_file *m, struct pid_namespace *ns,
+				struct pid *pid, struct task_struct *task)
+{
+	seq_printf(m, "%d\n", task->patch_state);
+	return 0;
+}
+#endif /* CONFIG_LIVEPATCH */
+
+#ifdef CONFIG_STACKLEAK_METRICS
+static int proc_stack_depth(struct seq_file *m, struct pid_namespace *ns,
+				struct pid *pid, struct task_struct *task)
+{
+	unsigned long prev_depth = THREAD_SIZE -
+				(task->prev_lowest_stack & (THREAD_SIZE - 1));
+	unsigned long depth = THREAD_SIZE -
+				(task->lowest_stack & (THREAD_SIZE - 1));
+
+	seq_printf(m, "previous stack depth: %lu\nstack depth: %lu\n",
+							prev_depth, depth);
+	return 0;
+}
+#endif /* CONFIG_STACKLEAK_METRICS */
+
+/*
+ * Thread groups
+ */
+static const struct file_operations proc_task_operations;
+static const struct inode_operations proc_task_inode_operations;
+
+static const struct pid_entry tgid_base_stuff[] = {
+	DIR("task",       S_IRUGO|S_IXUGO, proc_task_inode_operations, proc_task_operations),
+	DIR("fd",         S_IRUSR|S_IXUSR, proc_fd_inode_operations, proc_fd_operations),
+	DIR("map_files",  S_IRUSR|S_IXUSR, proc_map_files_inode_operations, proc_map_files_operations),
+	DIR("fdinfo",     S_IRUSR|S_IXUSR, proc_fdinfo_inode_operations, proc_fdinfo_operations),
+	DIR("ns",	  S_IRUSR|S_IXUGO, proc_ns_dir_inode_operations, proc_ns_dir_operations),
+#ifdef CONFIG_NET
+	DIR("net",        S_IRUGO|S_IXUGO, proc_net_inode_operations, proc_net_operations),
+#endif
+	REG("environ",    S_IRUSR, proc_environ_operations),
+	REG("auxv",       S_IRUSR, proc_auxv_operations),
+	ONE("status",     S_IRUGO, proc_pid_status),
+	ONE("personality", S_IRUSR, proc_pid_personality),
+	ONE("limits",	  S_IRUGO, proc_pid_limits),
+#ifdef CONFIG_SCHED_DEBUG
+	REG("sched",      S_IRUGO|S_IWUSR, proc_pid_sched_operations),
+#endif
+#ifdef CONFIG_SCHED_AUTOGROUP
+	REG("autogroup",  S_IRUGO|S_IWUSR, proc_pid_sched_autogroup_operations),
+#endif
+#ifdef CONFIG_TIME_NS
+	REG("timens_offsets",  S_IRUGO|S_IWUSR, proc_timens_offsets_operations),
+#endif
+	REG("comm",      S_IRUGO|S_IWUSR, proc_pid_set_comm_operations),
+#ifdef CONFIG_HAVE_ARCH_TRACEHOOK
+	ONE("syscall",    S_IRUSR, proc_pid_syscall),
+#endif
+	REG("cmdline",    S_IRUGO, proc_pid_cmdline_ops),
+	ONE("stat",       S_IRUGO, proc_tgid_stat),
+	ONE("statm",      S_IRUGO, proc_pid_statm),
+	REG("maps",       S_IRUGO, proc_pid_maps_operations),
+#ifdef CONFIG_NUMA
+	REG("numa_maps",  S_IRUGO, proc_pid_numa_maps_operations),
+#endif
+	REG("mem",        S_IRUSR|S_IWUSR, proc_mem_operations),
+	LNK("cwd",        proc_cwd_link),
+	LNK("root",       proc_root_link),
+	LNK("exe",        proc_exe_link),
+	REG("mounts",     S_IRUGO, proc_mounts_operations),
+	REG("mountinfo",  S_IRUGO, proc_mountinfo_operations),
+	REG("mountstats", S_IRUSR, proc_mountstats_operations),
+#ifdef CONFIG_PROC_PAGE_MONITOR
+	REG("clear_refs", S_IWUSR, proc_clear_refs_operations),
+	REG("smaps",      S_IRUGO, proc_pid_smaps_operations),
+	REG("smaps_rollup", S_IRUGO, proc_pid_smaps_rollup_operations),
+	REG("pagemap",    S_IRUSR, proc_pagemap_operations),
+#endif
+#ifdef CONFIG_SECURITY
+	DIR("attr",       S_IRUGO|S_IXUGO, proc_attr_dir_inode_operations, proc_attr_dir_operations),
+#endif
+#ifdef CONFIG_KALLSYMS
+	ONE("wchan",      S_IRUGO, proc_pid_wchan),
+#endif
+#ifdef CONFIG_STACKTRACE
+	ONE("stack",      S_IRUSR, proc_pid_stack),
+#endif
+#ifdef CONFIG_SCHED_INFO
+	ONE("schedstat",  S_IRUGO, proc_pid_schedstat),
+#endif
+#ifdef CONFIG_LATENCYTOP
+	REG("latency",  S_IRUGO, proc_lstats_operations),
+#endif
+#ifdef CONFIG_PROC_PID_CPUSET
+	ONE("cpuset",     S_IRUGO, proc_cpuset_show),
+#endif
+#ifdef CONFIG_CGROUPS
+	ONE("cgroup",  S_IRUGO, proc_cgroup_show),
+#endif
+#ifdef CONFIG_PROC_CPU_RESCTRL
+	ONE("cpu_resctrl_groups", S_IRUGO, proc_resctrl_show),
+#endif
+	ONE("oom_score",  S_IRUGO, proc_oom_score),
+	REG("oom_adj",    S_IRUGO|S_IWUSR, proc_oom_adj_operations),
+	REG("oom_score_adj", S_IRUGO|S_IWUSR, proc_oom_score_adj_operations),
+#ifdef CONFIG_AUDIT
+	REG("loginuid",   S_IWUSR|S_IRUGO, proc_loginuid_operations),
+	REG("sessionid",  S_IRUGO, proc_sessionid_operations),
+#endif
+#ifdef CONFIG_FAULT_INJECTION
+	REG("make-it-fail", S_IRUGO|S_IWUSR, proc_fault_inject_operations),
+	REG("fail-nth", 0644, proc_fail_nth_operations),
+#endif
+#ifdef CONFIG_ELF_CORE
+	REG("coredump_filter", S_IRUGO|S_IWUSR, proc_coredump_filter_operations),
+#endif
+#ifdef CONFIG_TASK_IO_ACCOUNTING
+	ONE("io",	S_IRUSR, proc_tgid_io_accounting),
+#endif
+#ifdef CONFIG_USER_NS
+	REG("uid_map",    S_IRUGO|S_IWUSR, proc_uid_map_operations),
+	REG("gid_map",    S_IRUGO|S_IWUSR, proc_gid_map_operations),
+	REG("projid_map", S_IRUGO|S_IWUSR, proc_projid_map_operations),
+	REG("setgroups",  S_IRUGO|S_IWUSR, proc_setgroups_operations),
+#endif
+#if defined(CONFIG_CHECKPOINT_RESTORE) && defined(CONFIG_POSIX_TIMERS)
+	REG("timers",	  S_IRUGO, proc_timers_operations),
+#endif
+	REG("timerslack_ns", S_IRUGO|S_IWUGO, proc_pid_set_timerslack_ns_operations),
+#ifdef CONFIG_LIVEPATCH
+	ONE("patch_state",  S_IRUSR, proc_pid_patch_state),
+#endif
+#ifdef CONFIG_STACKLEAK_METRICS
+	ONE("stack_depth", S_IRUGO, proc_stack_depth),
+#endif
+#ifdef CONFIG_PROC_PID_ARCH_STATUS
+	ONE("arch_status", S_IRUGO, proc_pid_arch_status),
+#endif
+};
+
+static int proc_tgid_base_readdir(struct file *file, struct dir_context *ctx)
+{
+	return proc_pident_readdir(file, ctx,
+				   tgid_base_stuff, ARRAY_SIZE(tgid_base_stuff));
+}
+
+static const struct file_operations proc_tgid_base_operations = {
+	.read		= generic_read_dir,
+	.iterate_shared	= proc_tgid_base_readdir,
+	.llseek		= generic_file_llseek,
+};
+
+struct pid *tgid_pidfd_to_pid(const struct file *file)
+{
+	if (file->f_op != &proc_tgid_base_operations)
+		return ERR_PTR(-EBADF);
+
+	return proc_pid(file_inode(file));
+}
+
+static struct dentry *proc_tgid_base_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
+{
+	return proc_pident_lookup(dir, dentry,
+				  tgid_base_stuff,
+				  tgid_base_stuff + ARRAY_SIZE(tgid_base_stuff));
+}
+
+static const struct inode_operations proc_tgid_base_inode_operations = {
+	.lookup		= proc_tgid_base_lookup,
+	.getattr	= pid_getattr,
+	.setattr	= proc_setattr,
+	.permission	= proc_pid_permission,
+};
+
+/**
+ * proc_flush_pid -  Remove dcache entries for @pid from the /proc dcache.
+ * @pid: pid that should be flushed.
+ *
+ * This function walks a list of inodes (that belong to any proc
+ * filesystem) that are attached to the pid and flushes them from
+ * the dentry cache.
+ *
+ * It is safe and reasonable to cache /proc entries for a task until
+ * that task exits.  After that they just clog up the dcache with
+ * useless entries, possibly causing useful dcache entries to be
+ * flushed instead.  This routine is provided to flush those useless
+ * dcache entries when a process is reaped.
+ *
+ * NOTE: This routine is just an optimization so it does not guarantee
+ *       that no dcache entries will exist after a process is reaped
+ *       it just makes it very unlikely that any will persist.
+ */
+
+void proc_flush_pid(struct pid *pid)
+{
+	proc_invalidate_siblings_dcache(&pid->inodes, &pid->lock);
+}
+
+static struct dentry *proc_pid_instantiate(struct dentry * dentry,
+				   struct task_struct *task, const void *ptr)
+{
+	struct inode *inode;
+
+	inode = proc_pid_make_base_inode(dentry->d_sb, task,
+					 S_IFDIR | S_IRUGO | S_IXUGO);
+	if (!inode)
+		return ERR_PTR(-ENOENT);
+
+	inode->i_op = &proc_tgid_base_inode_operations;
+	inode->i_fop = &proc_tgid_base_operations;
+	inode->i_flags|=S_IMMUTABLE;
+
+	set_nlink(inode, nlink_tgid);
+	pid_update_inode(task, inode);
+
+	d_set_d_op(dentry, &pid_dentry_operations);
+	return d_splice_alias(inode, dentry);
+}
+
+struct dentry *proc_pid_lookup(struct dentry *dentry, unsigned int flags)
+{
+	struct task_struct *task;
+	unsigned tgid;
+	struct proc_fs_info *fs_info;
+	struct pid_namespace *ns;
+	struct dentry *result = ERR_PTR(-ENOENT);
+
+	tgid = name_to_int(&dentry->d_name);
+	if (tgid == ~0U)
+		goto out;
+
+	fs_info = proc_sb_info(dentry->d_sb);
+	ns = fs_info->pid_ns;
+	rcu_read_lock();
+	task = find_task_by_pid_ns(tgid, ns);
+	if (task)
+		get_task_struct(task);
+	rcu_read_unlock();
+	if (!task)
+		goto out;
+
+	/* Limit procfs to only ptraceable tasks */
+	if (fs_info->hide_pid == HIDEPID_NOT_PTRACEABLE) {
+		if (!has_pid_permissions(fs_info, task, HIDEPID_NO_ACCESS))
+			goto out_put_task;
+	}
+
+	result = proc_pid_instantiate(dentry, task, NULL);
+out_put_task:
+	put_task_struct(task);
+out:
+	return result;
+}
+
+/*
+ * Find the first task with tgid >= tgid
+ *
+ */
+struct tgid_iter {
+	unsigned int tgid;
+	struct task_struct *task;
+};
+static struct tgid_iter next_tgid(struct pid_namespace *ns, struct tgid_iter iter)
+{
+	struct pid *pid;
+
+	if (iter.task)
+		put_task_struct(iter.task);
+	rcu_read_lock();
+retry:
+	iter.task = NULL;
+	pid = find_ge_pid(iter.tgid, ns);
+	if (pid) {
+		iter.tgid = pid_nr_ns(pid, ns);
+		iter.task = pid_task(pid, PIDTYPE_TGID);
+		if (!iter.task) {
+			iter.tgid += 1;
+			goto retry;
+		}
+		get_task_struct(iter.task);
+	}
+	rcu_read_unlock();
+	return iter;
+}
+
+#define TGID_OFFSET (FIRST_PROCESS_ENTRY + 2)
+
+/* for the /proc/ directory itself, after non-process stuff has been done */
+int proc_pid_readdir(struct file *file, struct dir_context *ctx)
+{
+	struct tgid_iter iter;
+	struct proc_fs_info *fs_info = proc_sb_info(file_inode(file)->i_sb);
+	struct pid_namespace *ns = proc_pid_ns(file_inode(file)->i_sb);
+	loff_t pos = ctx->pos;
+
+	if (pos >= PID_MAX_LIMIT + TGID_OFFSET)
+		return 0;
+
+	if (pos == TGID_OFFSET - 2) {
+		struct inode *inode = d_inode(fs_info->proc_self);
+		if (!dir_emit(ctx, "self", 4, inode->i_ino, DT_LNK))
+			return 0;
+		ctx->pos = pos = pos + 1;
+	}
+	if (pos == TGID_OFFSET - 1) {
+		struct inode *inode = d_inode(fs_info->proc_thread_self);
+		if (!dir_emit(ctx, "thread-self", 11, inode->i_ino, DT_LNK))
+			return 0;
+		ctx->pos = pos = pos + 1;
+	}
+	iter.tgid = pos - TGID_OFFSET;
+	iter.task = NULL;
+	for (iter = next_tgid(ns, iter);
+	     iter.task;
+	     iter.tgid += 1, iter = next_tgid(ns, iter)) {
+		char name[10 + 1];
+		unsigned int len;
+
+		cond_resched();
+		if (!has_pid_permissions(fs_info, iter.task, HIDEPID_INVISIBLE))
+			continue;
+
+		len = snprintf(name, sizeof(name), "%u", iter.tgid);
+		ctx->pos = iter.tgid + TGID_OFFSET;
+		if (!proc_fill_cache(file, ctx, name, len,
+				     proc_pid_instantiate, iter.task, NULL)) {
+			put_task_struct(iter.task);
+			return 0;
+		}
+	}
+	ctx->pos = PID_MAX_LIMIT + TGID_OFFSET;
+	return 0;
+}
+
+/*
+ * proc_tid_comm_permission is a special permission function exclusively
+ * used for the node /proc/<pid>/task/<tid>/comm.
+ * It bypasses generic permission checks in the case where a task of the same
+ * task group attempts to access the node.
+ * The rationale behind this is that glibc and bionic access this node for
+ * cross thread naming (pthread_set/getname_np(!self)). However, if
+ * PR_SET_DUMPABLE gets set to 0 this node among others becomes uid=0 gid=0,
+ * which locks out the cross thread naming implementation.
+ * This function makes sure that the node is always accessible for members of
+ * same thread group.
+ */
+static int proc_tid_comm_permission(struct inode *inode, int mask)
+{
+	bool is_same_tgroup;
+	struct task_struct *task;
+
+	task = get_proc_task(inode);
+	if (!task)
+		return -ESRCH;
+	is_same_tgroup = same_thread_group(current, task);
+	put_task_struct(task);
+
+	if (likely(is_same_tgroup && !(mask & MAY_EXEC))) {
+		/* This file (/proc/<pid>/task/<tid>/comm) can always be
+		 * read or written by the members of the corresponding
+		 * thread group.
+		 */
+		return 0;
+	}
+
+	return generic_permission(inode, mask);
+}
+
+static const struct inode_operations proc_tid_comm_inode_operations = {
+		.setattr	= proc_setattr,
+		.permission	= proc_tid_comm_permission,
+};
+
+/*
+ * Tasks
+ */
+static const struct pid_entry tid_base_stuff[] = {
+	DIR("fd",        S_IRUSR|S_IXUSR, proc_fd_inode_operations, proc_fd_operations),
+	DIR("fdinfo",    S_IRUSR|S_IXUSR, proc_fdinfo_inode_operations, proc_fdinfo_operations),
+	DIR("ns",	 S_IRUSR|S_IXUGO, proc_ns_dir_inode_operations, proc_ns_dir_operations),
+#ifdef CONFIG_NET
+	DIR("net",        S_IRUGO|S_IXUGO, proc_net_inode_operations, proc_net_operations),
+#endif
+	REG("environ",   S_IRUSR, proc_environ_operations),
+	REG("auxv",      S_IRUSR, proc_auxv_operations),
+	ONE("status",    S_IRUGO, proc_pid_status),
+	ONE("personality", S_IRUSR, proc_pid_personality),
+	ONE("limits",	 S_IRUGO, proc_pid_limits),
+#ifdef CONFIG_SCHED_DEBUG
+	REG("sched",     S_IRUGO|S_IWUSR, proc_pid_sched_operations),
+#endif
+	NOD("comm",      S_IFREG|S_IRUGO|S_IWUSR,
+			 &proc_tid_comm_inode_operations,
+			 &proc_pid_set_comm_operations, {}),
+#ifdef CONFIG_HAVE_ARCH_TRACEHOOK
+	ONE("syscall",   S_IRUSR, proc_pid_syscall),
+#endif
+	REG("cmdline",   S_IRUGO, proc_pid_cmdline_ops),
+	ONE("stat",      S_IRUGO, proc_tid_stat),
+	ONE("statm",     S_IRUGO, proc_pid_statm),
+	REG("maps",      S_IRUGO, proc_pid_maps_operations),
+#ifdef CONFIG_PROC_CHILDREN
+	REG("children",  S_IRUGO, proc_tid_children_operations),
+#endif
+#ifdef CONFIG_NUMA
+	REG("numa_maps", S_IRUGO, proc_pid_numa_maps_operations),
+#endif
+	REG("mem",       S_IRUSR|S_IWUSR, proc_mem_operations),
+	LNK("cwd",       proc_cwd_link),
+	LNK("root",      proc_root_link),
+	LNK("exe",       proc_exe_link),
+	REG("mounts",    S_IRUGO, proc_mounts_operations),
+	REG("mountinfo",  S_IRUGO, proc_mountinfo_operations),
+#ifdef CONFIG_PROC_PAGE_MONITOR
+	REG("clear_refs", S_IWUSR, proc_clear_refs_operations),
+	REG("smaps",     S_IRUGO, proc_pid_smaps_operations),
+	REG("smaps_rollup", S_IRUGO, proc_pid_smaps_rollup_operations),
+	REG("pagemap",    S_IRUSR, proc_pagemap_operations),
+#endif
+#ifdef CONFIG_SECURITY
+	DIR("attr",      S_IRUGO|S_IXUGO, proc_attr_dir_inode_operations, proc_attr_dir_operations),
+#endif
+#ifdef CONFIG_KALLSYMS
+	ONE("wchan",     S_IRUGO, proc_pid_wchan),
+#endif
+#ifdef CONFIG_STACKTRACE
+	ONE("stack",      S_IRUSR, proc_pid_stack),
+#endif
+#ifdef CONFIG_SCHED_INFO
+	ONE("schedstat", S_IRUGO, proc_pid_schedstat),
+#endif
+#ifdef CONFIG_LATENCYTOP
+	REG("latency",  S_IRUGO, proc_lstats_operations),
+#endif
+#ifdef CONFIG_PROC_PID_CPUSET
+	ONE("cpuset",    S_IRUGO, proc_cpuset_show),
+#endif
+#ifdef CONFIG_CGROUPS
+	ONE("cgroup",  S_IRUGO, proc_cgroup_show),
+#endif
+#ifdef CONFIG_PROC_CPU_RESCTRL
+	ONE("cpu_resctrl_groups", S_IRUGO, proc_resctrl_show),
+#endif
+	ONE("oom_score", S_IRUGO, proc_oom_score),
+	REG("oom_adj",   S_IRUGO|S_IWUSR, proc_oom_adj_operations),
+	REG("oom_score_adj", S_IRUGO|S_IWUSR, proc_oom_score_adj_operations),
+#ifdef CONFIG_AUDIT
+	REG("loginuid",  S_IWUSR|S_IRUGO, proc_loginuid_operations),
+	REG("sessionid",  S_IRUGO, proc_sessionid_operations),
+#endif
+#ifdef CONFIG_FAULT_INJECTION
+	REG("make-it-fail", S_IRUGO|S_IWUSR, proc_fault_inject_operations),
+	REG("fail-nth", 0644, proc_fail_nth_operations),
+#endif
+#ifdef CONFIG_TASK_IO_ACCOUNTING
+	ONE("io",	S_IRUSR, proc_tid_io_accounting),
+#endif
+#ifdef CONFIG_USER_NS
+	REG("uid_map",    S_IRUGO|S_IWUSR, proc_uid_map_operations),
+	REG("gid_map",    S_IRUGO|S_IWUSR, proc_gid_map_operations),
+	REG("projid_map", S_IRUGO|S_IWUSR, proc_projid_map_operations),
+	REG("setgroups",  S_IRUGO|S_IWUSR, proc_setgroups_operations),
+#endif
+#ifdef CONFIG_LIVEPATCH
+	ONE("patch_state",  S_IRUSR, proc_pid_patch_state),
+#endif
+#ifdef CONFIG_PROC_PID_ARCH_STATUS
+	ONE("arch_status", S_IRUGO, proc_pid_arch_status),
+#endif
+};
+
+static int proc_tid_base_readdir(struct file *file, struct dir_context *ctx)
+{
+	return proc_pident_readdir(file, ctx,
+				   tid_base_stuff, ARRAY_SIZE(tid_base_stuff));
+}
+
+static struct dentry *proc_tid_base_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
+{
+	return proc_pident_lookup(dir, dentry,
+				  tid_base_stuff,
+				  tid_base_stuff + ARRAY_SIZE(tid_base_stuff));
+}
+
+static const struct file_operations proc_tid_base_operations = {
+	.read		= generic_read_dir,
+	.iterate_shared	= proc_tid_base_readdir,
+	.llseek		= generic_file_llseek,
+};
+
+static const struct inode_operations proc_tid_base_inode_operations = {
+	.lookup		= proc_tid_base_lookup,
+	.getattr	= pid_getattr,
+	.setattr	= proc_setattr,
+};
+
+static struct dentry *proc_task_instantiate(struct dentry *dentry,
+	struct task_struct *task, const void *ptr)
+{
+	struct inode *inode;
+	inode = proc_pid_make_base_inode(dentry->d_sb, task,
+					 S_IFDIR | S_IRUGO | S_IXUGO);
+	if (!inode)
+		return ERR_PTR(-ENOENT);
+
+	inode->i_op = &proc_tid_base_inode_operations;
+	inode->i_fop = &proc_tid_base_operations;
+	inode->i_flags |= S_IMMUTABLE;
+
+	set_nlink(inode, nlink_tid);
+	pid_update_inode(task, inode);
+
+	d_set_d_op(dentry, &pid_dentry_operations);
+	return d_splice_alias(inode, dentry);
+}
+
+static struct dentry *proc_task_lookup(struct inode *dir, struct dentry * dentry, unsigned int flags)
+{
+	struct task_struct *task;
+	struct task_struct *leader = get_proc_task(dir);
+	unsigned tid;
+	struct proc_fs_info *fs_info;
+	struct pid_namespace *ns;
+	struct dentry *result = ERR_PTR(-ENOENT);
+
+	if (!leader)
+		goto out_no_task;
+
+	tid = name_to_int(&dentry->d_name);
+	if (tid == ~0U)
+		goto out;
+
+	fs_info = proc_sb_info(dentry->d_sb);
+	ns = fs_info->pid_ns;
+	rcu_read_lock();
+	task = find_task_by_pid_ns(tid, ns);
+	if (task)
+		get_task_struct(task);
+	rcu_read_unlock();
+	if (!task)
+		goto out;
+	if (!same_thread_group(leader, task))
+		goto out_drop_task;
+
+	result = proc_task_instantiate(dentry, task, NULL);
+out_drop_task:
+	put_task_struct(task);
+out:
+	put_task_struct(leader);
+out_no_task:
+	return result;
+}
+
+/*
+ * Find the first tid of a thread group to return to user space.
+ *
+ * Usually this is just the thread group leader, but if the users
+ * buffer was too small or there was a seek into the middle of the
+ * directory we have more work todo.
+ *
+ * In the case of a short read we start with find_task_by_pid.
+ *
+ * In the case of a seek we start with the leader and walk nr
+ * threads past it.
+ */
+static struct task_struct *first_tid(struct pid *pid, int tid, loff_t f_pos,
+					struct pid_namespace *ns)
+{
+	struct task_struct *pos, *task;
+	unsigned long nr = f_pos;
+
+	if (nr != f_pos)	/* 32bit overflow? */
+		return NULL;
+
+	rcu_read_lock();
+	task = pid_task(pid, PIDTYPE_PID);
+	if (!task)
+		goto fail;
+
+	/* Attempt to start with the tid of a thread */
+	if (tid && nr) {
+		pos = find_task_by_pid_ns(tid, ns);
+		if (pos && same_thread_group(pos, task))
+			goto found;
+	}
+
+	/* If nr exceeds the number of threads there is nothing todo */
+	if (nr >= get_nr_threads(task))
+		goto fail;
+
+	/* If we haven't found our starting place yet start
+	 * with the leader and walk nr threads forward.
+	 */
+	pos = task = task->group_leader;
+	do {
+		if (!nr--)
+			goto found;
+	} while_each_thread(task, pos);
+fail:
+	pos = NULL;
+	goto out;
+found:
+	get_task_struct(pos);
+out:
+	rcu_read_unlock();
+	return pos;
+}
+
+/*
+ * Find the next thread in the thread list.
+ * Return NULL if there is an error or no next thread.
+ *
+ * The reference to the input task_struct is released.
+ */
+static struct task_struct *next_tid(struct task_struct *start)
+{
+	struct task_struct *pos = NULL;
+	rcu_read_lock();
+	if (pid_alive(start)) {
+		pos = next_thread(start);
+		if (thread_group_leader(pos))
+			pos = NULL;
+		else
+			get_task_struct(pos);
+	}
+	rcu_read_unlock();
+	put_task_struct(start);
+	return pos;
+}
+
+/* for the /proc/TGID/task/ directories */
+static int proc_task_readdir(struct file *file, struct dir_context *ctx)
+{
+	struct inode *inode = file_inode(file);
+	struct task_struct *task;
+	struct pid_namespace *ns;
+	int tid;
+
+	if (proc_inode_is_dead(inode))
+		return -ENOENT;
+
+	if (!dir_emit_dots(file, ctx))
+		return 0;
+
+	/* f_version caches the tgid value that the last readdir call couldn't
+	 * return. lseek aka telldir automagically resets f_version to 0.
+	 */
+	ns = proc_pid_ns(inode->i_sb);
+	tid = (int)file->f_version;
+	file->f_version = 0;
+	for (task = first_tid(proc_pid(inode), tid, ctx->pos - 2, ns);
+	     task;
+	     task = next_tid(task), ctx->pos++) {
+		char name[10 + 1];
+		unsigned int len;
+		tid = task_pid_nr_ns(task, ns);
+		len = snprintf(name, sizeof(name), "%u", tid);
+		if (!proc_fill_cache(file, ctx, name, len,
+				proc_task_instantiate, task, NULL)) {
+			/* returning this tgid failed, save it as the first
+			 * pid for the next readir call */
+			file->f_version = (u64)tid;
+			put_task_struct(task);
+			break;
+		}
+	}
+
+	return 0;
+}
+
+static int proc_task_getattr(const struct path *path, struct kstat *stat,
+			     u32 request_mask, unsigned int query_flags)
+{
+	struct inode *inode = d_inode(path->dentry);
+	struct task_struct *p = get_proc_task(inode);
+	generic_fillattr(inode, stat);
+
+	if (p) {
+		stat->nlink += get_nr_threads(p);
+		put_task_struct(p);
+	}
+
+	return 0;
+}
+
+static const struct inode_operations proc_task_inode_operations = {
+	.lookup		= proc_task_lookup,
+	.getattr	= proc_task_getattr,
+	.setattr	= proc_setattr,
+	.permission	= proc_pid_permission,
+};
+
+static const struct file_operations proc_task_operations = {
+	.read		= generic_read_dir,
+	.iterate_shared	= proc_task_readdir,
+	.llseek		= generic_file_llseek,
+};
+
+void __init set_proc_pid_nlink(void)
+{
+	nlink_tid = pid_entry_nlink(tid_base_stuff, ARRAY_SIZE(tid_base_stuff));
+	nlink_tgid = pid_entry_nlink(tgid_base_stuff, ARRAY_SIZE(tgid_base_stuff));
+}