1 files changed, 381 insertions, 0 deletions
diff --git a/fs/proc/fd.c b/fs/proc/fd.c
new file mode 100644
index 000000000..913bef0d2
--- /dev/null
+++ b/fs/proc/fd.c
@@ -0,0 +1,381 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/sched/signal.h>
+#include <linux/errno.h>
+#include <linux/dcache.h>
+#include <linux/path.h>
+#include <linux/fdtable.h>
+#include <linux/namei.h>
+#include <linux/pid.h>
+#include <linux/ptrace.h>
+#include <linux/security.h>
+#include <linux/file.h>
+#include <linux/seq_file.h>
+#include <linux/fs.h>
+
+#include <linux/proc_fs.h>
+
+#include "../mount.h"
+#include "internal.h"
+#include "fd.h"
+
+static int seq_show(struct seq_file *m, void *v)
+{
+	struct files_struct *files = NULL;
+	int f_flags = 0, ret = -ENOENT;
+	struct file *file = NULL;
+	struct task_struct *task;
+
+	task = get_proc_task(m->private);
+	if (!task)
+		return -ENOENT;
+
+	task_lock(task);
+	files = task->files;
+	if (files) {
+		unsigned int fd = proc_fd(m->private);
+
+		spin_lock(&files->file_lock);
+		file = files_lookup_fd_locked(files, fd);
+		if (file) {
+			struct fdtable *fdt = files_fdtable(files);
+
+			f_flags = file->f_flags;
+			if (close_on_exec(fd, fdt))
+				f_flags |= O_CLOEXEC;
+
+			get_file(file);
+			ret = 0;
+		}
+		spin_unlock(&files->file_lock);
+	}
+	task_unlock(task);
+	put_task_struct(task);
+
+	if (ret)
+		return ret;
+
+	seq_printf(m, "pos:\t%lli\nflags:\t0%o\nmnt_id:\t%i\nino:\t%lu\n",
+		   (long long)file->f_pos, f_flags,
+		   real_mount(file->f_path.mnt)->mnt_id,
+		   file_inode(file)->i_ino);
+
+	/* show_fd_locks() never deferences files so a stale value is safe */
+	show_fd_locks(m, file, files);
+	if (seq_has_overflowed(m))
+		goto out;
+
+	if (file->f_op->show_fdinfo)
+		file->f_op->show_fdinfo(m, file);
+
+out:
+	fput(file);
+	return 0;
+}
+
+static int proc_fdinfo_access_allowed(struct inode *inode)
+{
+	bool allowed = false;
+	struct task_struct *task = get_proc_task(inode);
+
+	if (!task)
+		return -ESRCH;
+
+	allowed = ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS);
+	put_task_struct(task);
+
+	if (!allowed)
+		return -EACCES;
+
+	return 0;
+}
+
+static int seq_fdinfo_open(struct inode *inode, struct file *file)
+{
+	int ret = proc_fdinfo_access_allowed(inode);
+
+	if (ret)
+		return ret;
+
+	return single_open(file, seq_show, inode);
+}
+
+static const struct file_operations proc_fdinfo_file_operations = {
+	.open		= seq_fdinfo_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
+static bool tid_fd_mode(struct task_struct *task, unsigned fd, fmode_t *mode)
+{
+	struct file *file;
+
+	rcu_read_lock();
+	file = task_lookup_fd_rcu(task, fd);
+	if (file)
+		*mode = file->f_mode;
+	rcu_read_unlock();
+	return !!file;
+}
+
+static void tid_fd_update_inode(struct task_struct *task, struct inode *inode,
+				fmode_t f_mode)
+{
+	task_dump_owner(task, 0, &inode->i_uid, &inode->i_gid);
+
+	if (S_ISLNK(inode->i_mode)) {
+		unsigned i_mode = S_IFLNK;
+		if (f_mode & FMODE_READ)
+			i_mode |= S_IRUSR | S_IXUSR;
+		if (f_mode & FMODE_WRITE)
+			i_mode |= S_IWUSR | S_IXUSR;
+		inode->i_mode = i_mode;
+	}
+	security_task_to_inode(task, inode);
+}
+
+static int tid_fd_revalidate(struct dentry *dentry, unsigned int flags)
+{
+	struct task_struct *task;
+	struct inode *inode;
+	unsigned int fd;
+
+	if (flags & LOOKUP_RCU)
+		return -ECHILD;
+
+	inode = d_inode(dentry);
+	task = get_proc_task(inode);
+	fd = proc_fd(inode);
+
+	if (task) {
+		fmode_t f_mode;
+		if (tid_fd_mode(task, fd, &f_mode)) {
+			tid_fd_update_inode(task, inode, f_mode);
+			put_task_struct(task);
+			return 1;
+		}
+		put_task_struct(task);
+	}
+	return 0;
+}
+
+static const struct dentry_operations tid_fd_dentry_operations = {
+	.d_revalidate	= tid_fd_revalidate,
+	.d_delete	= pid_delete_dentry,
+};
+
+static int proc_fd_link(struct dentry *dentry, struct path *path)
+{
+	struct task_struct *task;
+	int ret = -ENOENT;
+
+	task = get_proc_task(d_inode(dentry));
+	if (task) {
+		unsigned int fd = proc_fd(d_inode(dentry));
+		struct file *fd_file;
+
+		fd_file = fget_task(task, fd);
+		if (fd_file) {
+			*path = fd_file->f_path;
+			path_get(&fd_file->f_path);
+			ret = 0;
+			fput(fd_file);
+		}
+		put_task_struct(task);
+	}
+
+	return ret;
+}
+
+struct fd_data {
+	fmode_t mode;
+	unsigned fd;
+};
+
+static struct dentry *proc_fd_instantiate(struct dentry *dentry,
+	struct task_struct *task, const void *ptr)
+{
+	const struct fd_data *data = ptr;
+	struct proc_inode *ei;
+	struct inode *inode;
+
+	inode = proc_pid_make_inode(dentry->d_sb, task, S_IFLNK);
+	if (!inode)
+		return ERR_PTR(-ENOENT);
+
+	ei = PROC_I(inode);
+	ei->fd = data->fd;
+
+	inode->i_op = &proc_pid_link_inode_operations;
+	inode->i_size = 64;
+
+	ei->op.proc_get_link = proc_fd_link;
+	tid_fd_update_inode(task, inode, data->mode);
+
+	d_set_d_op(dentry, &tid_fd_dentry_operations);
+	return d_splice_alias(inode, dentry);
+}
+
+static struct dentry *proc_lookupfd_common(struct inode *dir,
+					   struct dentry *dentry,
+					   instantiate_t instantiate)
+{
+	struct task_struct *task = get_proc_task(dir);
+	struct fd_data data = {.fd = name_to_int(&dentry->d_name)};
+	struct dentry *result = ERR_PTR(-ENOENT);
+
+	if (!task)
+		goto out_no_task;
+	if (data.fd == ~0U)
+		goto out;
+	if (!tid_fd_mode(task, data.fd, &data.mode))
+		goto out;
+
+	result = instantiate(dentry, task, &data);
+out:
+	put_task_struct(task);
+out_no_task:
+	return result;
+}
+
+static int proc_readfd_common(struct file *file, struct dir_context *ctx,
+			      instantiate_t instantiate)
+{
+	struct task_struct *p = get_proc_task(file_inode(file));
+	unsigned int fd;
+
+	if (!p)
+		return -ENOENT;
+
+	if (!dir_emit_dots(file, ctx))
+		goto out;
+
+	rcu_read_lock();
+	for (fd = ctx->pos - 2;; fd++) {
+		struct file *f;
+		struct fd_data data;
+		char name[10 + 1];
+		unsigned int len;
+
+		f = task_lookup_next_fd_rcu(p, &fd);
+		ctx->pos = fd + 2LL;
+		if (!f)
+			break;
+		data.mode = f->f_mode;
+		rcu_read_unlock();
+		data.fd = fd;
+
+		len = snprintf(name, sizeof(name), "%u", fd);
+		if (!proc_fill_cache(file, ctx,
+				     name, len, instantiate, p,
+				     &data))
+			goto out;
+		cond_resched();
+		rcu_read_lock();
+	}
+	rcu_read_unlock();
+out:
+	put_task_struct(p);
+	return 0;
+}
+
+static int proc_readfd(struct file *file, struct dir_context *ctx)
+{
+	return proc_readfd_common(file, ctx, proc_fd_instantiate);
+}
+
+const struct file_operations proc_fd_operations = {
+	.read		= generic_read_dir,
+	.iterate_shared	= proc_readfd,
+	.llseek		= generic_file_llseek,
+};
+
+static struct dentry *proc_lookupfd(struct inode *dir, struct dentry *dentry,
+				    unsigned int flags)
+{
+	return proc_lookupfd_common(dir, dentry, proc_fd_instantiate);
+}
+
+/*
+ * /proc/pid/fd needs a special permission handler so that a process can still
+ * access /proc/self/fd after it has executed a setuid().
+ */
+int proc_fd_permission(struct user_namespace *mnt_userns,
+		       struct inode *inode, int mask)
+{
+	struct task_struct *p;
+	int rv;
+
+	rv = generic_permission(&init_user_ns, inode, mask);
+	if (rv == 0)
+		return rv;
+
+	rcu_read_lock();
+	p = pid_task(proc_pid(inode), PIDTYPE_PID);
+	if (p && same_thread_group(p, current))
+		rv = 0;
+	rcu_read_unlock();
+
+	return rv;
+}
+
+const struct inode_operations proc_fd_inode_operations = {
+	.lookup		= proc_lookupfd,
+	.permission	= proc_fd_permission,
+	.setattr	= proc_setattr,
+};
+
+static struct dentry *proc_fdinfo_instantiate(struct dentry *dentry,
+	struct task_struct *task, const void *ptr)
+{
+	const struct fd_data *data = ptr;
+	struct proc_inode *ei;
+	struct inode *inode;
+
+	inode = proc_pid_make_inode(dentry->d_sb, task, S_IFREG | S_IRUGO);
+	if (!inode)
+		return ERR_PTR(-ENOENT);
+
+	ei = PROC_I(inode);
+	ei->fd = data->fd;
+
+	inode->i_fop = &proc_fdinfo_file_operations;
+	tid_fd_update_inode(task, inode, 0);
+
+	d_set_d_op(dentry, &tid_fd_dentry_operations);
+	return d_splice_alias(inode, dentry);
+}
+
+static struct dentry *
+proc_lookupfdinfo(struct inode *dir, struct dentry *dentry, unsigned int flags)
+{
+	return proc_lookupfd_common(dir, dentry, proc_fdinfo_instantiate);
+}
+
+static int proc_readfdinfo(struct file *file, struct dir_context *ctx)
+{
+	return proc_readfd_common(file, ctx,
+				  proc_fdinfo_instantiate);
+}
+
+static int proc_open_fdinfo(struct inode *inode, struct file *file)
+{
+	int ret = proc_fdinfo_access_allowed(inode);
+
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+const struct inode_operations proc_fdinfo_inode_operations = {
+	.lookup		= proc_lookupfdinfo,
+	.setattr	= proc_setattr,
+};
+
+const struct file_operations proc_fdinfo_operations = {
+	.open		= proc_open_fdinfo,
+	.read		= generic_read_dir,
+	.iterate_shared	= proc_readfdinfo,
+	.llseek		= generic_file_llseek,
+};