Adding upstream version 5.10.209.upstream/5.10.209upstream

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

1 files changed, 2109 insertions, 0 deletions

diff --git a/kernel/seccomp.c b/kernel/seccomp.c
new file mode 100644
index 000000000..305f0eca1
--- /dev/null
+++ b/kernel/seccomp.c
@@ -0,0 +1,2109 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * linux/kernel/seccomp.c
+ *
+ * Copyright 2004-2005  Andrea Arcangeli <andrea@cpushare.com>
+ *
+ * Copyright (C) 2012 Google, Inc.
+ * Will Drewry <wad@chromium.org>
+ *
+ * This defines a simple but solid secure-computing facility.
+ *
+ * Mode 1 uses a fixed list of allowed system calls.
+ * Mode 2 allows user-defined system call filters in the form
+ *        of Berkeley Packet Filters/Linux Socket Filters.
+ */
+#define pr_fmt(fmt) "seccomp: " fmt
+
+#include <linux/refcount.h>
+#include <linux/audit.h>
+#include <linux/compat.h>
+#include <linux/coredump.h>
+#include <linux/kmemleak.h>
+#include <linux/nospec.h>
+#include <linux/prctl.h>
+#include <linux/sched.h>
+#include <linux/sched/task_stack.h>
+#include <linux/seccomp.h>
+#include <linux/slab.h>
+#include <linux/syscalls.h>
+#include <linux/sysctl.h>
+
+#ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
+#include <asm/syscall.h>
+#endif
+
+#ifdef CONFIG_SECCOMP_FILTER
+#include <linux/file.h>
+#include <linux/filter.h>
+#include <linux/pid.h>
+#include <linux/ptrace.h>
+#include <linux/capability.h>
+#include <linux/tracehook.h>
+#include <linux/uaccess.h>
+#include <linux/anon_inodes.h>
+#include <linux/lockdep.h>
+
+/*
+ * When SECCOMP_IOCTL_NOTIF_ID_VALID was first introduced, it had the
+ * wrong direction flag in the ioctl number. This is the broken one,
+ * which the kernel needs to keep supporting until all userspaces stop
+ * using the wrong command number.
+ */
+#define SECCOMP_IOCTL_NOTIF_ID_VALID_WRONG_DIR	SECCOMP_IOR(2, __u64)
+
+enum notify_state {
+	SECCOMP_NOTIFY_INIT,
+	SECCOMP_NOTIFY_SENT,
+	SECCOMP_NOTIFY_REPLIED,
+};
+
+struct seccomp_knotif {
+	/* The struct pid of the task whose filter triggered the notification */
+	struct task_struct *task;
+
+	/* The "cookie" for this request; this is unique for this filter. */
+	u64 id;
+
+	/*
+	 * The seccomp data. This pointer is valid the entire time this
+	 * notification is active, since it comes from __seccomp_filter which
+	 * eclipses the entire lifecycle here.
+	 */
+	const struct seccomp_data *data;
+
+	/*
+	 * Notification states. When SECCOMP_RET_USER_NOTIF is returned, a
+	 * struct seccomp_knotif is created and starts out in INIT. Once the
+	 * handler reads the notification off of an FD, it transitions to SENT.
+	 * If a signal is received the state transitions back to INIT and
+	 * another message is sent. When the userspace handler replies, state
+	 * transitions to REPLIED.
+	 */
+	enum notify_state state;
+
+	/* The return values, only valid when in SECCOMP_NOTIFY_REPLIED */
+	int error;
+	long val;
+	u32 flags;
+
+	/*
+	 * Signals when this has changed states, such as the listener
+	 * dying, a new seccomp addfd message, or changing to REPLIED
+	 */
+	struct completion ready;
+
+	struct list_head list;
+
+	/* outstanding addfd requests */
+	struct list_head addfd;
+};
+
+/**
+ * struct seccomp_kaddfd - container for seccomp_addfd ioctl messages
+ *
+ * @file: A reference to the file to install in the other task
+ * @fd: The fd number to install it at. If the fd number is -1, it means the
+ *      installing process should allocate the fd as normal.
+ * @flags: The flags for the new file descriptor. At the moment, only O_CLOEXEC
+ *         is allowed.
+ * @ret: The return value of the installing process. It is set to the fd num
+ *       upon success (>= 0).
+ * @completion: Indicates that the installing process has completed fd
+ *              installation, or gone away (either due to successful
+ *              reply, or signal)
+ *
+ */
+struct seccomp_kaddfd {
+	struct file *file;
+	int fd;
+	unsigned int flags;
+
+	/* To only be set on reply */
+	int ret;
+	struct completion completion;
+	struct list_head list;
+};
+
+/**
+ * struct notification - container for seccomp userspace notifications. Since
+ * most seccomp filters will not have notification listeners attached and this
+ * structure is fairly large, we store the notification-specific stuff in a
+ * separate structure.
+ *
+ * @request: A semaphore that users of this notification can wait on for
+ *           changes. Actual reads and writes are still controlled with
+ *           filter->notify_lock.
+ * @next_id: The id of the next request.
+ * @notifications: A list of struct seccomp_knotif elements.
+ */
+struct notification {
+	struct semaphore request;
+	u64 next_id;
+	struct list_head notifications;
+};
+
+/**
+ * struct seccomp_filter - container for seccomp BPF programs
+ *
+ * @refs: Reference count to manage the object lifetime.
+ *	  A filter's reference count is incremented for each directly
+ *	  attached task, once for the dependent filter, and if
+ *	  requested for the user notifier. When @refs reaches zero,
+ *	  the filter can be freed.
+ * @users: A filter's @users count is incremented for each directly
+ *         attached task (filter installation, fork(), thread_sync),
+ *	   and once for the dependent filter (tracked in filter->prev).
+ *	   When it reaches zero it indicates that no direct or indirect
+ *	   users of that filter exist. No new tasks can get associated with
+ *	   this filter after reaching 0. The @users count is always smaller
+ *	   or equal to @refs. Hence, reaching 0 for @users does not mean
+ *	   the filter can be freed.
+ * @log: true if all actions except for SECCOMP_RET_ALLOW should be logged
+ * @prev: points to a previously installed, or inherited, filter
+ * @prog: the BPF program to evaluate
+ * @notif: the struct that holds all notification related information
+ * @notify_lock: A lock for all notification-related accesses.
+ * @wqh: A wait queue for poll if a notifier is in use.
+ *
+ * seccomp_filter objects are organized in a tree linked via the @prev
+ * pointer.  For any task, it appears to be a singly-linked list starting
+ * with current->seccomp.filter, the most recently attached or inherited filter.
+ * However, multiple filters may share a @prev node, by way of fork(), which
+ * results in a unidirectional tree existing in memory.  This is similar to
+ * how namespaces work.
+ *
+ * seccomp_filter objects should never be modified after being attached
+ * to a task_struct (other than @refs).
+ */
+struct seccomp_filter {
+	refcount_t refs;
+	refcount_t users;
+	bool log;
+	struct seccomp_filter *prev;
+	struct bpf_prog *prog;
+	struct notification *notif;
+	struct mutex notify_lock;
+	wait_queue_head_t wqh;
+};
+
+/* Limit any path through the tree to 256KB worth of instructions. */
+#define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter))
+
+/*
+ * Endianness is explicitly ignored and left for BPF program authors to manage
+ * as per the specific architecture.
+ */
+static void populate_seccomp_data(struct seccomp_data *sd)
+{
+	/*
+	 * Instead of using current_pt_reg(), we're already doing the work
+	 * to safely fetch "current", so just use "task" everywhere below.
+	 */
+	struct task_struct *task = current;
+	struct pt_regs *regs = task_pt_regs(task);
+	unsigned long args[6];
+
+	sd->nr = syscall_get_nr(task, regs);
+	sd->arch = syscall_get_arch(task);
+	syscall_get_arguments(task, regs, args);
+	sd->args[0] = args[0];
+	sd->args[1] = args[1];
+	sd->args[2] = args[2];
+	sd->args[3] = args[3];
+	sd->args[4] = args[4];
+	sd->args[5] = args[5];
+	sd->instruction_pointer = KSTK_EIP(task);
+}
+
+/**
+ *	seccomp_check_filter - verify seccomp filter code
+ *	@filter: filter to verify
+ *	@flen: length of filter
+ *
+ * Takes a previously checked filter (by bpf_check_classic) and
+ * redirects all filter code that loads struct sk_buff data
+ * and related data through seccomp_bpf_load.  It also
+ * enforces length and alignment checking of those loads.
+ *
+ * Returns 0 if the rule set is legal or -EINVAL if not.
+ */
+static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen)
+{
+	int pc;
+	for (pc = 0; pc < flen; pc++) {
+		struct sock_filter *ftest = &filter[pc];
+		u16 code = ftest->code;
+		u32 k = ftest->k;
+
+		switch (code) {
+		case BPF_LD | BPF_W | BPF_ABS:
+			ftest->code = BPF_LDX | BPF_W | BPF_ABS;
+			/* 32-bit aligned and not out of bounds. */
+			if (k >= sizeof(struct seccomp_data) || k & 3)
+				return -EINVAL;
+			continue;
+		case BPF_LD | BPF_W | BPF_LEN:
+			ftest->code = BPF_LD | BPF_IMM;
+			ftest->k = sizeof(struct seccomp_data);
+			continue;
+		case BPF_LDX | BPF_W | BPF_LEN:
+			ftest->code = BPF_LDX | BPF_IMM;
+			ftest->k = sizeof(struct seccomp_data);
+			continue;
+		/* Explicitly include allowed calls. */
+		case BPF_RET | BPF_K:
+		case BPF_RET | BPF_A:
+		case BPF_ALU | BPF_ADD | BPF_K:
+		case BPF_ALU | BPF_ADD | BPF_X:
+		case BPF_ALU | BPF_SUB | BPF_K:
+		case BPF_ALU | BPF_SUB | BPF_X:
+		case BPF_ALU | BPF_MUL | BPF_K:
+		case BPF_ALU | BPF_MUL | BPF_X:
+		case BPF_ALU | BPF_DIV | BPF_K:
+		case BPF_ALU | BPF_DIV | BPF_X:
+		case BPF_ALU | BPF_AND | BPF_K:
+		case BPF_ALU | BPF_AND | BPF_X:
+		case BPF_ALU | BPF_OR | BPF_K:
+		case BPF_ALU | BPF_OR | BPF_X:
+		case BPF_ALU | BPF_XOR | BPF_K:
+		case BPF_ALU | BPF_XOR | BPF_X:
+		case BPF_ALU | BPF_LSH | BPF_K:
+		case BPF_ALU | BPF_LSH | BPF_X:
+		case BPF_ALU | BPF_RSH | BPF_K:
+		case BPF_ALU | BPF_RSH | BPF_X:
+		case BPF_ALU | BPF_NEG:
+		case BPF_LD | BPF_IMM:
+		case BPF_LDX | BPF_IMM:
+		case BPF_MISC | BPF_TAX:
+		case BPF_MISC | BPF_TXA:
+		case BPF_LD | BPF_MEM:
+		case BPF_LDX | BPF_MEM:
+		case BPF_ST:
+		case BPF_STX:
+		case BPF_JMP | BPF_JA:
+		case BPF_JMP | BPF_JEQ | BPF_K:
+		case BPF_JMP | BPF_JEQ | BPF_X:
+		case BPF_JMP | BPF_JGE | BPF_K:
+		case BPF_JMP | BPF_JGE | BPF_X:
+		case BPF_JMP | BPF_JGT | BPF_K:
+		case BPF_JMP | BPF_JGT | BPF_X:
+		case BPF_JMP | BPF_JSET | BPF_K:
+		case BPF_JMP | BPF_JSET | BPF_X:
+			continue;
+		default:
+			return -EINVAL;
+		}
+	}
+	return 0;
+}
+
+/**
+ * seccomp_run_filters - evaluates all seccomp filters against @sd
+ * @sd: optional seccomp data to be passed to filters
+ * @match: stores struct seccomp_filter that resulted in the return value,
+ *         unless filter returned SECCOMP_RET_ALLOW, in which case it will
+ *         be unchanged.
+ *
+ * Returns valid seccomp BPF response codes.
+ */
+#define ACTION_ONLY(ret) ((s32)((ret) & (SECCOMP_RET_ACTION_FULL)))
+static u32 seccomp_run_filters(const struct seccomp_data *sd,
+			       struct seccomp_filter **match)
+{
+	u32 ret = SECCOMP_RET_ALLOW;
+	/* Make sure cross-thread synced filter points somewhere sane. */
+	struct seccomp_filter *f =
+			READ_ONCE(current->seccomp.filter);
+
+	/* Ensure unexpected behavior doesn't result in failing open. */
+	if (WARN_ON(f == NULL))
+		return SECCOMP_RET_KILL_PROCESS;
+
+	/*
+	 * All filters in the list are evaluated and the lowest BPF return
+	 * value always takes priority (ignoring the DATA).
+	 */
+	for (; f; f = f->prev) {
+		u32 cur_ret = bpf_prog_run_pin_on_cpu(f->prog, sd);
+
+		if (ACTION_ONLY(cur_ret) < ACTION_ONLY(ret)) {
+			ret = cur_ret;
+			*match = f;
+		}
+	}
+	return ret;
+}
+#endif /* CONFIG_SECCOMP_FILTER */
+
+static inline bool seccomp_may_assign_mode(unsigned long seccomp_mode)
+{
+	assert_spin_locked(&current->sighand->siglock);
+
+	if (current->seccomp.mode && current->seccomp.mode != seccomp_mode)
+		return false;
+
+	return true;
+}
+
+void __weak arch_seccomp_spec_mitigate(struct task_struct *task) { }
+
+static inline void seccomp_assign_mode(struct task_struct *task,
+				       unsigned long seccomp_mode,
+				       unsigned long flags)
+{
+	assert_spin_locked(&task->sighand->siglock);
+
+	task->seccomp.mode = seccomp_mode;
+	/*
+	 * Make sure TIF_SECCOMP cannot be set before the mode (and
+	 * filter) is set.
+	 */
+	smp_mb__before_atomic();
+	/* Assume default seccomp processes want spec flaw mitigation. */
+	if ((flags & SECCOMP_FILTER_FLAG_SPEC_ALLOW) == 0)
+		arch_seccomp_spec_mitigate(task);
+	set_tsk_thread_flag(task, TIF_SECCOMP);
+}
+
+#ifdef CONFIG_SECCOMP_FILTER
+/* Returns 1 if the parent is an ancestor of the child. */
+static int is_ancestor(struct seccomp_filter *parent,
+		       struct seccomp_filter *child)
+{
+	/* NULL is the root ancestor. */
+	if (parent == NULL)
+		return 1;
+	for (; child; child = child->prev)
+		if (child == parent)
+			return 1;
+	return 0;
+}
+
+/**
+ * seccomp_can_sync_threads: checks if all threads can be synchronized
+ *
+ * Expects sighand and cred_guard_mutex locks to be held.
+ *
+ * Returns 0 on success, -ve on error, or the pid of a thread which was
+ * either not in the correct seccomp mode or did not have an ancestral
+ * seccomp filter.
+ */
+static inline pid_t seccomp_can_sync_threads(void)
+{
+	struct task_struct *thread, *caller;
+
+	BUG_ON(!mutex_is_locked(&current->signal->cred_guard_mutex));
+	assert_spin_locked(&current->sighand->siglock);
+
+	/* Validate all threads being eligible for synchronization. */
+	caller = current;
+	for_each_thread(caller, thread) {
+		pid_t failed;
+
+		/* Skip current, since it is initiating the sync. */
+		if (thread == caller)
+			continue;
+
+		if (thread->seccomp.mode == SECCOMP_MODE_DISABLED ||
+		    (thread->seccomp.mode == SECCOMP_MODE_FILTER &&
+		     is_ancestor(thread->seccomp.filter,
+				 caller->seccomp.filter)))
+			continue;
+
+		/* Return the first thread that cannot be synchronized. */
+		failed = task_pid_vnr(thread);
+		/* If the pid cannot be resolved, then return -ESRCH */
+		if (WARN_ON(failed == 0))
+			failed = -ESRCH;
+		return failed;
+	}
+
+	return 0;
+}
+
+static inline void seccomp_filter_free(struct seccomp_filter *filter)
+{
+	if (filter) {
+		bpf_prog_destroy(filter->prog);
+		kfree(filter);
+	}
+}
+
+static void __seccomp_filter_orphan(struct seccomp_filter *orig)
+{
+	while (orig && refcount_dec_and_test(&orig->users)) {
+		if (waitqueue_active(&orig->wqh))
+			wake_up_poll(&orig->wqh, EPOLLHUP);
+		orig = orig->prev;
+	}
+}
+
+static void __put_seccomp_filter(struct seccomp_filter *orig)
+{
+	/* Clean up single-reference branches iteratively. */
+	while (orig && refcount_dec_and_test(&orig->refs)) {
+		struct seccomp_filter *freeme = orig;
+		orig = orig->prev;
+		seccomp_filter_free(freeme);
+	}
+}
+
+static void __seccomp_filter_release(struct seccomp_filter *orig)
+{
+	/* Notify about any unused filters in the task's former filter tree. */
+	__seccomp_filter_orphan(orig);
+	/* Finally drop all references to the task's former tree. */
+	__put_seccomp_filter(orig);
+}
+
+/**
+ * seccomp_filter_release - Detach the task from its filter tree,
+ *			    drop its reference count, and notify
+ *			    about unused filters
+ *
+ * This function should only be called when the task is exiting as
+ * it detaches it from its filter tree. As such, READ_ONCE() and
+ * barriers are not needed here, as would normally be needed.
+ */
+void seccomp_filter_release(struct task_struct *tsk)
+{
+	struct seccomp_filter *orig = tsk->seccomp.filter;
+
+	/* Detach task from its filter tree. */
+	tsk->seccomp.filter = NULL;
+	__seccomp_filter_release(orig);
+}
+
+/**
+ * seccomp_sync_threads: sets all threads to use current's filter
+ *
+ * Expects sighand and cred_guard_mutex locks to be held, and for
+ * seccomp_can_sync_threads() to have returned success already
+ * without dropping the locks.
+ *
+ */
+static inline void seccomp_sync_threads(unsigned long flags)
+{
+	struct task_struct *thread, *caller;
+
+	BUG_ON(!mutex_is_locked(&current->signal->cred_guard_mutex));
+	assert_spin_locked(&current->sighand->siglock);
+
+	/* Synchronize all threads. */
+	caller = current;
+	for_each_thread(caller, thread) {
+		/* Skip current, since it needs no changes. */
+		if (thread == caller)
+			continue;
+
+		/* Get a task reference for the new leaf node. */
+		get_seccomp_filter(caller);
+
+		/*
+		 * Drop the task reference to the shared ancestor since
+		 * current's path will hold a reference.  (This also
+		 * allows a put before the assignment.)
+		 */
+		__seccomp_filter_release(thread->seccomp.filter);
+
+		/* Make our new filter tree visible. */
+		smp_store_release(&thread->seccomp.filter,
+				  caller->seccomp.filter);
+		atomic_set(&thread->seccomp.filter_count,
+			   atomic_read(&caller->seccomp.filter_count));
+
+		/*
+		 * Don't let an unprivileged task work around
+		 * the no_new_privs restriction by creating
+		 * a thread that sets it up, enters seccomp,
+		 * then dies.
+		 */
+		if (task_no_new_privs(caller))
+			task_set_no_new_privs(thread);
+
+		/*
+		 * Opt the other thread into seccomp if needed.
+		 * As threads are considered to be trust-realm
+		 * equivalent (see ptrace_may_access), it is safe to
+		 * allow one thread to transition the other.
+		 */
+		if (thread->seccomp.mode == SECCOMP_MODE_DISABLED)
+			seccomp_assign_mode(thread, SECCOMP_MODE_FILTER,
+					    flags);
+	}
+}
+
+/**
+ * seccomp_prepare_filter: Prepares a seccomp filter for use.
+ * @fprog: BPF program to install
+ *
+ * Returns filter on success or an ERR_PTR on failure.
+ */
+static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog)
+{
+	struct seccomp_filter *sfilter;
+	int ret;
+	const bool save_orig = IS_ENABLED(CONFIG_CHECKPOINT_RESTORE);
+
+	if (fprog->len == 0 || fprog->len > BPF_MAXINSNS)
+		return ERR_PTR(-EINVAL);
+
+	BUG_ON(INT_MAX / fprog->len < sizeof(struct sock_filter));
+
+	/*
+	 * Installing a seccomp filter requires that the task has
+	 * CAP_SYS_ADMIN in its namespace or be running with no_new_privs.
+	 * This avoids scenarios where unprivileged tasks can affect the
+	 * behavior of privileged children.
+	 */
+	if (!task_no_new_privs(current) &&
+			!ns_capable_noaudit(current_user_ns(), CAP_SYS_ADMIN))
+		return ERR_PTR(-EACCES);
+
+	/* Allocate a new seccomp_filter */
+	sfilter = kzalloc(sizeof(*sfilter), GFP_KERNEL | __GFP_NOWARN);
+	if (!sfilter)
+		return ERR_PTR(-ENOMEM);
+
+	mutex_init(&sfilter->notify_lock);
+	ret = bpf_prog_create_from_user(&sfilter->prog, fprog,
+					seccomp_check_filter, save_orig);
+	if (ret < 0) {
+		kfree(sfilter);
+		return ERR_PTR(ret);
+	}
+
+	refcount_set(&sfilter->refs, 1);
+	refcount_set(&sfilter->users, 1);
+	init_waitqueue_head(&sfilter->wqh);
+
+	return sfilter;
+}
+
+/**
+ * seccomp_prepare_user_filter - prepares a user-supplied sock_fprog
+ * @user_filter: pointer to the user data containing a sock_fprog.
+ *
+ * Returns 0 on success and non-zero otherwise.
+ */
+static struct seccomp_filter *
+seccomp_prepare_user_filter(const char __user *user_filter)
+{
+	struct sock_fprog fprog;
+	struct seccomp_filter *filter = ERR_PTR(-EFAULT);
+
+#ifdef CONFIG_COMPAT
+	if (in_compat_syscall()) {
+		struct compat_sock_fprog fprog32;
+		if (copy_from_user(&fprog32, user_filter, sizeof(fprog32)))
+			goto out;
+		fprog.len = fprog32.len;
+		fprog.filter = compat_ptr(fprog32.filter);
+	} else /* falls through to the if below. */
+#endif
+	if (copy_from_user(&fprog, user_filter, sizeof(fprog)))
+		goto out;
+	filter = seccomp_prepare_filter(&fprog);
+out:
+	return filter;
+}
+
+/**
+ * seccomp_attach_filter: validate and attach filter
+ * @flags:  flags to change filter behavior
+ * @filter: seccomp filter to add to the current process
+ *
+ * Caller must be holding current->sighand->siglock lock.
+ *
+ * Returns 0 on success, -ve on error, or
+ *   - in TSYNC mode: the pid of a thread which was either not in the correct
+ *     seccomp mode or did not have an ancestral seccomp filter
+ *   - in NEW_LISTENER mode: the fd of the new listener
+ */
+static long seccomp_attach_filter(unsigned int flags,
+				  struct seccomp_filter *filter)
+{
+	unsigned long total_insns;
+	struct seccomp_filter *walker;
+
+	assert_spin_locked(&current->sighand->siglock);
+
+	/* Validate resulting filter length. */
+	total_insns = filter->prog->len;
+	for (walker = current->seccomp.filter; walker; walker = walker->prev)
+		total_insns += walker->prog->len + 4;  /* 4 instr penalty */
+	if (total_insns > MAX_INSNS_PER_PATH)
+		return -ENOMEM;
+
+	/* If thread sync has been requested, check that it is possible. */
+	if (flags & SECCOMP_FILTER_FLAG_TSYNC) {
+		int ret;
+
+		ret = seccomp_can_sync_threads();
+		if (ret) {
+			if (flags & SECCOMP_FILTER_FLAG_TSYNC_ESRCH)
+				return -ESRCH;
+			else
+				return ret;
+		}
+	}
+
+	/* Set log flag, if present. */
+	if (flags & SECCOMP_FILTER_FLAG_LOG)
+		filter->log = true;
+
+	/*
+	 * If there is an existing filter, make it the prev and don't drop its
+	 * task reference.
+	 */
+	filter->prev = current->seccomp.filter;
+	current->seccomp.filter = filter;
+	atomic_inc(&current->seccomp.filter_count);
+
+	/* Now that the new filter is in place, synchronize to all threads. */
+	if (flags & SECCOMP_FILTER_FLAG_TSYNC)
+		seccomp_sync_threads(flags);
+
+	return 0;
+}
+
+static void __get_seccomp_filter(struct seccomp_filter *filter)
+{
+	refcount_inc(&filter->refs);
+}
+
+/* get_seccomp_filter - increments the reference count of the filter on @tsk */
+void get_seccomp_filter(struct task_struct *tsk)
+{
+	struct seccomp_filter *orig = tsk->seccomp.filter;
+	if (!orig)
+		return;
+	__get_seccomp_filter(orig);
+	refcount_inc(&orig->users);
+}
+
+static void seccomp_init_siginfo(kernel_siginfo_t *info, int syscall, int reason)
+{
+	clear_siginfo(info);
+	info->si_signo = SIGSYS;
+	info->si_code = SYS_SECCOMP;
+	info->si_call_addr = (void __user *)KSTK_EIP(current);
+	info->si_errno = reason;
+	info->si_arch = syscall_get_arch(current);
+	info->si_syscall = syscall;
+}
+
+/**
+ * seccomp_send_sigsys - signals the task to allow in-process syscall emulation
+ * @syscall: syscall number to send to userland
+ * @reason: filter-supplied reason code to send to userland (via si_errno)
+ *
+ * Forces a SIGSYS with a code of SYS_SECCOMP and related sigsys info.
+ */
+static void seccomp_send_sigsys(int syscall, int reason)
+{
+	struct kernel_siginfo info;
+	seccomp_init_siginfo(&info, syscall, reason);
+	force_sig_info(&info);
+}
+#endif	/* CONFIG_SECCOMP_FILTER */
+
+/* For use with seccomp_actions_logged */
+#define SECCOMP_LOG_KILL_PROCESS	(1 << 0)
+#define SECCOMP_LOG_KILL_THREAD		(1 << 1)
+#define SECCOMP_LOG_TRAP		(1 << 2)
+#define SECCOMP_LOG_ERRNO		(1 << 3)
+#define SECCOMP_LOG_TRACE		(1 << 4)
+#define SECCOMP_LOG_LOG			(1 << 5)
+#define SECCOMP_LOG_ALLOW		(1 << 6)
+#define SECCOMP_LOG_USER_NOTIF		(1 << 7)
+
+static u32 seccomp_actions_logged = SECCOMP_LOG_KILL_PROCESS |
+				    SECCOMP_LOG_KILL_THREAD  |
+				    SECCOMP_LOG_TRAP  |
+				    SECCOMP_LOG_ERRNO |
+				    SECCOMP_LOG_USER_NOTIF |
+				    SECCOMP_LOG_TRACE |
+				    SECCOMP_LOG_LOG;
+
+static inline void seccomp_log(unsigned long syscall, long signr, u32 action,
+			       bool requested)
+{
+	bool log = false;
+
+	switch (action) {
+	case SECCOMP_RET_ALLOW:
+		break;
+	case SECCOMP_RET_TRAP:
+		log = requested && seccomp_actions_logged & SECCOMP_LOG_TRAP;
+		break;
+	case SECCOMP_RET_ERRNO:
+		log = requested && seccomp_actions_logged & SECCOMP_LOG_ERRNO;
+		break;
+	case SECCOMP_RET_TRACE:
+		log = requested && seccomp_actions_logged & SECCOMP_LOG_TRACE;
+		break;
+	case SECCOMP_RET_USER_NOTIF:
+		log = requested && seccomp_actions_logged & SECCOMP_LOG_USER_NOTIF;
+		break;
+	case SECCOMP_RET_LOG:
+		log = seccomp_actions_logged & SECCOMP_LOG_LOG;
+		break;
+	case SECCOMP_RET_KILL_THREAD:
+		log = seccomp_actions_logged & SECCOMP_LOG_KILL_THREAD;
+		break;
+	case SECCOMP_RET_KILL_PROCESS:
+	default:
+		log = seccomp_actions_logged & SECCOMP_LOG_KILL_PROCESS;
+	}
+
+	/*
+	 * Emit an audit message when the action is RET_KILL_*, RET_LOG, or the
+	 * FILTER_FLAG_LOG bit was set. The admin has the ability to silence
+	 * any action from being logged by removing the action name from the
+	 * seccomp_actions_logged sysctl.
+	 */
+	if (!log)
+		return;
+
+	audit_seccomp(syscall, signr, action);
+}
+
+/*
+ * Secure computing mode 1 allows only read/write/exit/sigreturn.
+ * To be fully secure this must be combined with rlimit
+ * to limit the stack allocations too.
+ */
+static const int mode1_syscalls[] = {
+	__NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn,
+	-1, /* negative terminated */
+};
+
+static void __secure_computing_strict(int this_syscall)
+{
+	const int *allowed_syscalls = mode1_syscalls;
+#ifdef CONFIG_COMPAT
+	if (in_compat_syscall())
+		allowed_syscalls = get_compat_mode1_syscalls();
+#endif
+	do {
+		if (*allowed_syscalls == this_syscall)
+			return;
+	} while (*++allowed_syscalls != -1);
+
+#ifdef SECCOMP_DEBUG
+	dump_stack();
+#endif
+	seccomp_log(this_syscall, SIGKILL, SECCOMP_RET_KILL_THREAD, true);
+	do_exit(SIGKILL);
+}
+
+#ifndef CONFIG_HAVE_ARCH_SECCOMP_FILTER
+void secure_computing_strict(int this_syscall)
+{
+	int mode = current->seccomp.mode;
+
+	if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
+	    unlikely(current->ptrace & PT_SUSPEND_SECCOMP))
+		return;
+
+	if (mode == SECCOMP_MODE_DISABLED)
+		return;
+	else if (mode == SECCOMP_MODE_STRICT)
+		__secure_computing_strict(this_syscall);
+	else
+		BUG();
+}
+#else
+
+#ifdef CONFIG_SECCOMP_FILTER
+static u64 seccomp_next_notify_id(struct seccomp_filter *filter)
+{
+	/*
+	 * Note: overflow is ok here, the id just needs to be unique per
+	 * filter.
+	 */
+	lockdep_assert_held(&filter->notify_lock);
+	return filter->notif->next_id++;
+}
+
+static void seccomp_handle_addfd(struct seccomp_kaddfd *addfd)
+{
+	/*
+	 * Remove the notification, and reset the list pointers, indicating
+	 * that it has been handled.
+	 */
+	list_del_init(&addfd->list);
+	addfd->ret = receive_fd_replace(addfd->fd, addfd->file, addfd->flags);
+	complete(&addfd->completion);
+}
+
+static int seccomp_do_user_notification(int this_syscall,
+					struct seccomp_filter *match,
+					const struct seccomp_data *sd)
+{
+	int err;
+	u32 flags = 0;
+	long ret = 0;
+	struct seccomp_knotif n = {};
+	struct seccomp_kaddfd *addfd, *tmp;
+
+	mutex_lock(&match->notify_lock);
+	err = -ENOSYS;
+	if (!match->notif)
+		goto out;
+
+	n.task = current;
+	n.state = SECCOMP_NOTIFY_INIT;
+	n.data = sd;
+	n.id = seccomp_next_notify_id(match);
+	init_completion(&n.ready);
+	list_add(&n.list, &match->notif->notifications);
+	INIT_LIST_HEAD(&n.addfd);
+
+	up(&match->notif->request);
+	wake_up_poll(&match->wqh, EPOLLIN | EPOLLRDNORM);
+
+	/*
+	 * This is where we wait for a reply from userspace.
+	 */
+	do {
+		mutex_unlock(&match->notify_lock);
+		err = wait_for_completion_interruptible(&n.ready);
+		mutex_lock(&match->notify_lock);
+		if (err != 0)
+			goto interrupted;
+
+		addfd = list_first_entry_or_null(&n.addfd,
+						 struct seccomp_kaddfd, list);
+		/* Check if we were woken up by a addfd message */
+		if (addfd)
+			seccomp_handle_addfd(addfd);
+
+	}  while (n.state != SECCOMP_NOTIFY_REPLIED);
+
+	ret = n.val;
+	err = n.error;
+	flags = n.flags;
+
+interrupted:
+	/* If there were any pending addfd calls, clear them out */
+	list_for_each_entry_safe(addfd, tmp, &n.addfd, list) {
+		/* The process went away before we got a chance to handle it */
+		addfd->ret = -ESRCH;
+		list_del_init(&addfd->list);
+		complete(&addfd->completion);
+	}
+
+	/*
+	 * Note that it's possible the listener died in between the time when
+	 * we were notified of a response (or a signal) and when we were able to
+	 * re-acquire the lock, so only delete from the list if the
+	 * notification actually exists.
+	 *
+	 * Also note that this test is only valid because there's no way to
+	 * *reattach* to a notifier right now. If one is added, we'll need to
+	 * keep track of the notif itself and make sure they match here.
+	 */
+	if (match->notif)
+		list_del(&n.list);
+out:
+	mutex_unlock(&match->notify_lock);
+
+	/* Userspace requests to continue the syscall. */
+	if (flags & SECCOMP_USER_NOTIF_FLAG_CONTINUE)
+		return 0;
+
+	syscall_set_return_value(current, current_pt_regs(),
+				 err, ret);
+	return -1;
+}
+
+static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
+			    const bool recheck_after_trace)
+{
+	u32 filter_ret, action;
+	struct seccomp_filter *match = NULL;
+	int data;
+	struct seccomp_data sd_local;
+
+	/*
+	 * Make sure that any changes to mode from another thread have
+	 * been seen after TIF_SECCOMP was seen.
+	 */
+	rmb();
+
+	if (!sd) {
+		populate_seccomp_data(&sd_local);
+		sd = &sd_local;
+	}
+
+	filter_ret = seccomp_run_filters(sd, &match);
+	data = filter_ret & SECCOMP_RET_DATA;
+	action = filter_ret & SECCOMP_RET_ACTION_FULL;
+
+	switch (action) {
+	case SECCOMP_RET_ERRNO:
+		/* Set low-order bits as an errno, capped at MAX_ERRNO. */
+		if (data > MAX_ERRNO)
+			data = MAX_ERRNO;
+		syscall_set_return_value(current, current_pt_regs(),
+					 -data, 0);
+		goto skip;
+
+	case SECCOMP_RET_TRAP:
+		/* Show the handler the original registers. */
+		syscall_rollback(current, current_pt_regs());
+		/* Let the filter pass back 16 bits of data. */
+		seccomp_send_sigsys(this_syscall, data);
+		goto skip;
+
+	case SECCOMP_RET_TRACE:
+		/* We've been put in this state by the ptracer already. */
+		if (recheck_after_trace)
+			return 0;
+
+		/* ENOSYS these calls if there is no tracer attached. */
+		if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) {
+			syscall_set_return_value(current,
+						 current_pt_regs(),
+						 -ENOSYS, 0);
+			goto skip;
+		}
+
+		/* Allow the BPF to provide the event message */
+		ptrace_event(PTRACE_EVENT_SECCOMP, data);
+		/*
+		 * The delivery of a fatal signal during event
+		 * notification may silently skip tracer notification,
+		 * which could leave us with a potentially unmodified
+		 * syscall that the tracer would have liked to have
+		 * changed. Since the process is about to die, we just
+		 * force the syscall to be skipped and let the signal
+		 * kill the process and correctly handle any tracer exit
+		 * notifications.
+		 */
+		if (fatal_signal_pending(current))
+			goto skip;
+		/* Check if the tracer forced the syscall to be skipped. */
+		this_syscall = syscall_get_nr(current, current_pt_regs());
+		if (this_syscall < 0)
+			goto skip;
+
+		/*
+		 * Recheck the syscall, since it may have changed. This
+		 * intentionally uses a NULL struct seccomp_data to force
+		 * a reload of all registers. This does not goto skip since
+		 * a skip would have already been reported.
+		 */
+		if (__seccomp_filter(this_syscall, NULL, true))
+			return -1;
+
+		return 0;
+
+	case SECCOMP_RET_USER_NOTIF:
+		if (seccomp_do_user_notification(this_syscall, match, sd))
+			goto skip;
+
+		return 0;
+
+	case SECCOMP_RET_LOG:
+		seccomp_log(this_syscall, 0, action, true);
+		return 0;
+
+	case SECCOMP_RET_ALLOW:
+		/*
+		 * Note that the "match" filter will always be NULL for
+		 * this action since SECCOMP_RET_ALLOW is the starting
+		 * state in seccomp_run_filters().
+		 */
+		return 0;
+
+	case SECCOMP_RET_KILL_THREAD:
+	case SECCOMP_RET_KILL_PROCESS:
+	default:
+		seccomp_log(this_syscall, SIGSYS, action, true);
+		/* Dump core only if this is the last remaining thread. */
+		if (action != SECCOMP_RET_KILL_THREAD ||
+		    get_nr_threads(current) == 1) {
+			kernel_siginfo_t info;
+
+			/* Show the original registers in the dump. */
+			syscall_rollback(current, current_pt_regs());
+			/* Trigger a manual coredump since do_exit skips it. */
+			seccomp_init_siginfo(&info, this_syscall, data);
+			do_coredump(&info);
+		}
+		if (action == SECCOMP_RET_KILL_THREAD)
+			do_exit(SIGSYS);
+		else
+			do_group_exit(SIGSYS);
+	}
+
+	unreachable();
+
+skip:
+	seccomp_log(this_syscall, 0, action, match ? match->log : false);
+	return -1;
+}
+#else
+static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
+			    const bool recheck_after_trace)
+{
+	BUG();
+
+	return -1;
+}
+#endif
+
+int __secure_computing(const struct seccomp_data *sd)
+{
+	int mode = current->seccomp.mode;
+	int this_syscall;
+
+	if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
+	    unlikely(current->ptrace & PT_SUSPEND_SECCOMP))
+		return 0;
+
+	this_syscall = sd ? sd->nr :
+		syscall_get_nr(current, current_pt_regs());
+
+	switch (mode) {
+	case SECCOMP_MODE_STRICT:
+		__secure_computing_strict(this_syscall);  /* may call do_exit */
+		return 0;
+	case SECCOMP_MODE_FILTER:
+		return __seccomp_filter(this_syscall, sd, false);
+	default:
+		BUG();
+	}
+}
+#endif /* CONFIG_HAVE_ARCH_SECCOMP_FILTER */
+
+long prctl_get_seccomp(void)
+{
+	return current->seccomp.mode;
+}
+
+/**
+ * seccomp_set_mode_strict: internal function for setting strict seccomp
+ *
+ * Once current->seccomp.mode is non-zero, it may not be changed.
+ *
+ * Returns 0 on success or -EINVAL on failure.
+ */
+static long seccomp_set_mode_strict(void)
+{
+	const unsigned long seccomp_mode = SECCOMP_MODE_STRICT;
+	long ret = -EINVAL;
+
+	spin_lock_irq(&current->sighand->siglock);
+
+	if (!seccomp_may_assign_mode(seccomp_mode))
+		goto out;
+
+#ifdef TIF_NOTSC
+	disable_TSC();
+#endif
+	seccomp_assign_mode(current, seccomp_mode, 0);
+	ret = 0;
+
+out:
+	spin_unlock_irq(&current->sighand->siglock);
+
+	return ret;
+}
+
+#ifdef CONFIG_SECCOMP_FILTER
+static void seccomp_notify_free(struct seccomp_filter *filter)
+{
+	kfree(filter->notif);
+	filter->notif = NULL;
+}
+
+static void seccomp_notify_detach(struct seccomp_filter *filter)
+{
+	struct seccomp_knotif *knotif;
+
+	if (!filter)
+		return;
+
+	mutex_lock(&filter->notify_lock);
+
+	/*
+	 * If this file is being closed because e.g. the task who owned it
+	 * died, let's wake everyone up who was waiting on us.
+	 */
+	list_for_each_entry(knotif, &filter->notif->notifications, list) {
+		if (knotif->state == SECCOMP_NOTIFY_REPLIED)
+			continue;
+
+		knotif->state = SECCOMP_NOTIFY_REPLIED;
+		knotif->error = -ENOSYS;
+		knotif->val = 0;
+
+		/*
+		 * We do not need to wake up any pending addfd messages, as
+		 * the notifier will do that for us, as this just looks
+		 * like a standard reply.
+		 */
+		complete(&knotif->ready);
+	}
+
+	seccomp_notify_free(filter);
+	mutex_unlock(&filter->notify_lock);
+}
+
+static int seccomp_notify_release(struct inode *inode, struct file *file)
+{
+	struct seccomp_filter *filter = file->private_data;
+
+	seccomp_notify_detach(filter);
+	__put_seccomp_filter(filter);
+	return 0;
+}
+
+/* must be called with notif_lock held */
+static inline struct seccomp_knotif *
+find_notification(struct seccomp_filter *filter, u64 id)
+{
+	struct seccomp_knotif *cur;
+
+	lockdep_assert_held(&filter->notify_lock);
+
+	list_for_each_entry(cur, &filter->notif->notifications, list) {
+		if (cur->id == id)
+			return cur;
+	}
+
+	return NULL;
+}
+
+
+static long seccomp_notify_recv(struct seccomp_filter *filter,
+				void __user *buf)
+{
+	struct seccomp_knotif *knotif = NULL, *cur;
+	struct seccomp_notif unotif;
+	ssize_t ret;
+
+	/* Verify that we're not given garbage to keep struct extensible. */
+	ret = check_zeroed_user(buf, sizeof(unotif));
+	if (ret < 0)
+		return ret;
+	if (!ret)
+		return -EINVAL;
+
+	memset(&unotif, 0, sizeof(unotif));
+
+	ret = down_interruptible(&filter->notif->request);
+	if (ret < 0)
+		return ret;
+
+	mutex_lock(&filter->notify_lock);
+	list_for_each_entry(cur, &filter->notif->notifications, list) {
+		if (cur->state == SECCOMP_NOTIFY_INIT) {
+			knotif = cur;
+			break;
+		}
+	}
+
+	/*
+	 * If we didn't find a notification, it could be that the task was
+	 * interrupted by a fatal signal between the time we were woken and
+	 * when we were able to acquire the rw lock.
+	 */
+	if (!knotif) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	unotif.id = knotif->id;
+	unotif.pid = task_pid_vnr(knotif->task);
+	unotif.data = *(knotif->data);
+
+	knotif->state = SECCOMP_NOTIFY_SENT;
+	wake_up_poll(&filter->wqh, EPOLLOUT | EPOLLWRNORM);
+	ret = 0;
+out:
+	mutex_unlock(&filter->notify_lock);
+
+	if (ret == 0 && copy_to_user(buf, &unotif, sizeof(unotif))) {
+		ret = -EFAULT;
+
+		/*
+		 * Userspace screwed up. To make sure that we keep this
+		 * notification alive, let's reset it back to INIT. It
+		 * may have died when we released the lock, so we need to make
+		 * sure it's still around.
+		 */
+		mutex_lock(&filter->notify_lock);
+		knotif = find_notification(filter, unotif.id);
+		if (knotif) {
+			knotif->state = SECCOMP_NOTIFY_INIT;
+			up(&filter->notif->request);
+		}
+		mutex_unlock(&filter->notify_lock);
+	}
+
+	return ret;
+}
+
+static long seccomp_notify_send(struct seccomp_filter *filter,
+				void __user *buf)
+{
+	struct seccomp_notif_resp resp = {};
+	struct seccomp_knotif *knotif;
+	long ret;
+
+	if (copy_from_user(&resp, buf, sizeof(resp)))
+		return -EFAULT;
+
+	if (resp.flags & ~SECCOMP_USER_NOTIF_FLAG_CONTINUE)
+		return -EINVAL;
+
+	if ((resp.flags & SECCOMP_USER_NOTIF_FLAG_CONTINUE) &&
+	    (resp.error || resp.val))
+		return -EINVAL;
+
+	ret = mutex_lock_interruptible(&filter->notify_lock);
+	if (ret < 0)
+		return ret;
+
+	knotif = find_notification(filter, resp.id);
+	if (!knotif) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	/* Allow exactly one reply. */
+	if (knotif->state != SECCOMP_NOTIFY_SENT) {
+		ret = -EINPROGRESS;
+		goto out;
+	}
+
+	ret = 0;
+	knotif->state = SECCOMP_NOTIFY_REPLIED;
+	knotif->error = resp.error;
+	knotif->val = resp.val;
+	knotif->flags = resp.flags;
+	complete(&knotif->ready);
+out:
+	mutex_unlock(&filter->notify_lock);
+	return ret;
+}
+
+static long seccomp_notify_id_valid(struct seccomp_filter *filter,
+				    void __user *buf)
+{
+	struct seccomp_knotif *knotif;
+	u64 id;
+	long ret;
+
+	if (copy_from_user(&id, buf, sizeof(id)))
+		return -EFAULT;
+
+	ret = mutex_lock_interruptible(&filter->notify_lock);
+	if (ret < 0)
+		return ret;
+
+	knotif = find_notification(filter, id);
+	if (knotif && knotif->state == SECCOMP_NOTIFY_SENT)
+		ret = 0;
+	else
+		ret = -ENOENT;
+
+	mutex_unlock(&filter->notify_lock);
+	return ret;
+}
+
+static long seccomp_notify_addfd(struct seccomp_filter *filter,
+				 struct seccomp_notif_addfd __user *uaddfd,
+				 unsigned int size)
+{
+	struct seccomp_notif_addfd addfd;
+	struct seccomp_knotif *knotif;
+	struct seccomp_kaddfd kaddfd;
+	int ret;
+
+	BUILD_BUG_ON(sizeof(addfd) < SECCOMP_NOTIFY_ADDFD_SIZE_VER0);
+	BUILD_BUG_ON(sizeof(addfd) != SECCOMP_NOTIFY_ADDFD_SIZE_LATEST);
+
+	if (size < SECCOMP_NOTIFY_ADDFD_SIZE_VER0 || size >= PAGE_SIZE)
+		return -EINVAL;
+
+	ret = copy_struct_from_user(&addfd, sizeof(addfd), uaddfd, size);
+	if (ret)
+		return ret;
+
+	if (addfd.newfd_flags & ~O_CLOEXEC)
+		return -EINVAL;
+
+	if (addfd.flags & ~SECCOMP_ADDFD_FLAG_SETFD)
+		return -EINVAL;
+
+	if (addfd.newfd && !(addfd.flags & SECCOMP_ADDFD_FLAG_SETFD))
+		return -EINVAL;
+
+	kaddfd.file = fget(addfd.srcfd);
+	if (!kaddfd.file)
+		return -EBADF;
+
+	kaddfd.flags = addfd.newfd_flags;
+	kaddfd.fd = (addfd.flags & SECCOMP_ADDFD_FLAG_SETFD) ?
+		    addfd.newfd : -1;
+	init_completion(&kaddfd.completion);
+
+	ret = mutex_lock_interruptible(&filter->notify_lock);
+	if (ret < 0)
+		goto out;
+
+	knotif = find_notification(filter, addfd.id);
+	if (!knotif) {
+		ret = -ENOENT;
+		goto out_unlock;
+	}
+
+	/*
+	 * We do not want to allow for FD injection to occur before the
+	 * notification has been picked up by a userspace handler, or after
+	 * the notification has been replied to.
+	 */
+	if (knotif->state != SECCOMP_NOTIFY_SENT) {
+		ret = -EINPROGRESS;
+		goto out_unlock;
+	}
+
+	list_add(&kaddfd.list, &knotif->addfd);
+	complete(&knotif->ready);
+	mutex_unlock(&filter->notify_lock);
+
+	/* Now we wait for it to be processed or be interrupted */
+	ret = wait_for_completion_interruptible(&kaddfd.completion);
+	if (ret == 0) {
+		/*
+		 * We had a successful completion. The other side has already
+		 * removed us from the addfd queue, and
+		 * wait_for_completion_interruptible has a memory barrier upon
+		 * success that lets us read this value directly without
+		 * locking.
+		 */
+		ret = kaddfd.ret;
+		goto out;
+	}
+
+	mutex_lock(&filter->notify_lock);
+	/*
+	 * Even though we were woken up by a signal and not a successful
+	 * completion, a completion may have happened in the mean time.
+	 *
+	 * We need to check again if the addfd request has been handled,
+	 * and if not, we will remove it from the queue.
+	 */
+	if (list_empty(&kaddfd.list))
+		ret = kaddfd.ret;
+	else
+		list_del(&kaddfd.list);
+
+out_unlock:
+	mutex_unlock(&filter->notify_lock);
+out:
+	fput(kaddfd.file);
+
+	return ret;
+}
+
+static long seccomp_notify_ioctl(struct file *file, unsigned int cmd,
+				 unsigned long arg)
+{
+	struct seccomp_filter *filter = file->private_data;
+	void __user *buf = (void __user *)arg;
+
+	/* Fixed-size ioctls */
+	switch (cmd) {
+	case SECCOMP_IOCTL_NOTIF_RECV:
+		return seccomp_notify_recv(filter, buf);
+	case SECCOMP_IOCTL_NOTIF_SEND:
+		return seccomp_notify_send(filter, buf);
+	case SECCOMP_IOCTL_NOTIF_ID_VALID_WRONG_DIR:
+	case SECCOMP_IOCTL_NOTIF_ID_VALID:
+		return seccomp_notify_id_valid(filter, buf);
+	}
+
+	/* Extensible Argument ioctls */
+#define EA_IOCTL(cmd)	((cmd) & ~(IOC_INOUT | IOCSIZE_MASK))
+	switch (EA_IOCTL(cmd)) {
+	case EA_IOCTL(SECCOMP_IOCTL_NOTIF_ADDFD):
+		return seccomp_notify_addfd(filter, buf, _IOC_SIZE(cmd));
+	default:
+		return -EINVAL;
+	}
+}
+
+static __poll_t seccomp_notify_poll(struct file *file,
+				    struct poll_table_struct *poll_tab)
+{
+	struct seccomp_filter *filter = file->private_data;
+	__poll_t ret = 0;
+	struct seccomp_knotif *cur;
+
+	poll_wait(file, &filter->wqh, poll_tab);
+
+	if (mutex_lock_interruptible(&filter->notify_lock) < 0)
+		return EPOLLERR;
+
+	list_for_each_entry(cur, &filter->notif->notifications, list) {
+		if (cur->state == SECCOMP_NOTIFY_INIT)
+			ret |= EPOLLIN | EPOLLRDNORM;
+		if (cur->state == SECCOMP_NOTIFY_SENT)
+			ret |= EPOLLOUT | EPOLLWRNORM;
+		if ((ret & EPOLLIN) && (ret & EPOLLOUT))
+			break;
+	}
+
+	mutex_unlock(&filter->notify_lock);
+
+	if (refcount_read(&filter->users) == 0)
+		ret |= EPOLLHUP;
+
+	return ret;
+}
+
+static const struct file_operations seccomp_notify_ops = {
+	.poll = seccomp_notify_poll,
+	.release = seccomp_notify_release,
+	.unlocked_ioctl = seccomp_notify_ioctl,
+	.compat_ioctl = seccomp_notify_ioctl,
+};
+
+static struct file *init_listener(struct seccomp_filter *filter)
+{
+	struct file *ret;
+
+	ret = ERR_PTR(-ENOMEM);
+	filter->notif = kzalloc(sizeof(*(filter->notif)), GFP_KERNEL);
+	if (!filter->notif)
+		goto out;
+
+	sema_init(&filter->notif->request, 0);
+	filter->notif->next_id = get_random_u64();
+	INIT_LIST_HEAD(&filter->notif->notifications);
+
+	ret = anon_inode_getfile("seccomp notify", &seccomp_notify_ops,
+				 filter, O_RDWR);
+	if (IS_ERR(ret))
+		goto out_notif;
+
+	/* The file has a reference to it now */
+	__get_seccomp_filter(filter);
+
+out_notif:
+	if (IS_ERR(ret))
+		seccomp_notify_free(filter);
+out:
+	return ret;
+}
+
+/*
+ * Does @new_child have a listener while an ancestor also has a listener?
+ * If so, we'll want to reject this filter.
+ * This only has to be tested for the current process, even in the TSYNC case,
+ * because TSYNC installs @child with the same parent on all threads.
+ * Note that @new_child is not hooked up to its parent at this point yet, so
+ * we use current->seccomp.filter.
+ */
+static bool has_duplicate_listener(struct seccomp_filter *new_child)
+{
+	struct seccomp_filter *cur;
+
+	/* must be protected against concurrent TSYNC */
+	lockdep_assert_held(&current->sighand->siglock);
+
+	if (!new_child->notif)
+		return false;
+	for (cur = current->seccomp.filter; cur; cur = cur->prev) {
+		if (cur->notif)
+			return true;
+	}
+
+	return false;
+}
+
+/**
+ * seccomp_set_mode_filter: internal function for setting seccomp filter
+ * @flags:  flags to change filter behavior
+ * @filter: struct sock_fprog containing filter
+ *
+ * This function may be called repeatedly to install additional filters.
+ * Every filter successfully installed will be evaluated (in reverse order)
+ * for each system call the task makes.
+ *
+ * Once current->seccomp.mode is non-zero, it may not be changed.
+ *
+ * Returns 0 on success or -EINVAL on failure.
+ */
+static long seccomp_set_mode_filter(unsigned int flags,
+				    const char __user *filter)
+{
+	const unsigned long seccomp_mode = SECCOMP_MODE_FILTER;
+	struct seccomp_filter *prepared = NULL;
+	long ret = -EINVAL;
+	int listener = -1;
+	struct file *listener_f = NULL;
+
+	/* Validate flags. */
+	if (flags & ~SECCOMP_FILTER_FLAG_MASK)
+		return -EINVAL;
+
+	/*
+	 * In the successful case, NEW_LISTENER returns the new listener fd.
+	 * But in the failure case, TSYNC returns the thread that died. If you
+	 * combine these two flags, there's no way to tell whether something
+	 * succeeded or failed. So, let's disallow this combination if the user
+	 * has not explicitly requested no errors from TSYNC.
+	 */
+	if ((flags & SECCOMP_FILTER_FLAG_TSYNC) &&
+	    (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) &&
+	    ((flags & SECCOMP_FILTER_FLAG_TSYNC_ESRCH) == 0))
+		return -EINVAL;
+
+	/* Prepare the new filter before holding any locks. */
+	prepared = seccomp_prepare_user_filter(filter);
+	if (IS_ERR(prepared))
+		return PTR_ERR(prepared);
+
+	if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) {
+		listener = get_unused_fd_flags(O_CLOEXEC);
+		if (listener < 0) {
+			ret = listener;
+			goto out_free;
+		}
+
+		listener_f = init_listener(prepared);
+		if (IS_ERR(listener_f)) {
+			put_unused_fd(listener);
+			ret = PTR_ERR(listener_f);
+			goto out_free;
+		}
+	}
+
+	/*
+	 * Make sure we cannot change seccomp or nnp state via TSYNC
+	 * while another thread is in the middle of calling exec.
+	 */
+	if (flags & SECCOMP_FILTER_FLAG_TSYNC &&
+	    mutex_lock_killable(&current->signal->cred_guard_mutex))
+		goto out_put_fd;
+
+	spin_lock_irq(&current->sighand->siglock);
+
+	if (!seccomp_may_assign_mode(seccomp_mode))
+		goto out;
+
+	if (has_duplicate_listener(prepared)) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	ret = seccomp_attach_filter(flags, prepared);
+	if (ret)
+		goto out;
+	/* Do not free the successfully attached filter. */
+	prepared = NULL;
+
+	seccomp_assign_mode(current, seccomp_mode, flags);
+out:
+	spin_unlock_irq(&current->sighand->siglock);
+	if (flags & SECCOMP_FILTER_FLAG_TSYNC)
+		mutex_unlock(&current->signal->cred_guard_mutex);
+out_put_fd:
+	if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) {
+		if (ret) {
+			listener_f->private_data = NULL;
+			fput(listener_f);
+			put_unused_fd(listener);
+			seccomp_notify_detach(prepared);
+		} else {
+			fd_install(listener, listener_f);
+			ret = listener;
+		}
+	}
+out_free:
+	seccomp_filter_free(prepared);
+	return ret;
+}
+#else
+static inline long seccomp_set_mode_filter(unsigned int flags,
+					   const char __user *filter)
+{
+	return -EINVAL;
+}
+#endif
+
+static long seccomp_get_action_avail(const char __user *uaction)
+{
+	u32 action;
+
+	if (copy_from_user(&action, uaction, sizeof(action)))
+		return -EFAULT;
+
+	switch (action) {
+	case SECCOMP_RET_KILL_PROCESS:
+	case SECCOMP_RET_KILL_THREAD:
+	case SECCOMP_RET_TRAP:
+	case SECCOMP_RET_ERRNO:
+	case SECCOMP_RET_USER_NOTIF:
+	case SECCOMP_RET_TRACE:
+	case SECCOMP_RET_LOG:
+	case SECCOMP_RET_ALLOW:
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	return 0;
+}
+
+static long seccomp_get_notif_sizes(void __user *usizes)
+{
+	struct seccomp_notif_sizes sizes = {
+		.seccomp_notif = sizeof(struct seccomp_notif),
+		.seccomp_notif_resp = sizeof(struct seccomp_notif_resp),
+		.seccomp_data = sizeof(struct seccomp_data),
+	};
+
+	if (copy_to_user(usizes, &sizes, sizeof(sizes)))
+		return -EFAULT;
+
+	return 0;
+}
+
+/* Common entry point for both prctl and syscall. */
+static long do_seccomp(unsigned int op, unsigned int flags,
+		       void __user *uargs)
+{
+	switch (op) {
+	case SECCOMP_SET_MODE_STRICT:
+		if (flags != 0 || uargs != NULL)
+			return -EINVAL;
+		return seccomp_set_mode_strict();
+	case SECCOMP_SET_MODE_FILTER:
+		return seccomp_set_mode_filter(flags, uargs);
+	case SECCOMP_GET_ACTION_AVAIL:
+		if (flags != 0)
+			return -EINVAL;
+
+		return seccomp_get_action_avail(uargs);
+	case SECCOMP_GET_NOTIF_SIZES:
+		if (flags != 0)
+			return -EINVAL;
+
+		return seccomp_get_notif_sizes(uargs);
+	default:
+		return -EINVAL;
+	}
+}
+
+SYSCALL_DEFINE3(seccomp, unsigned int, op, unsigned int, flags,
+			 void __user *, uargs)
+{
+	return do_seccomp(op, flags, uargs);
+}
+
+/**
+ * prctl_set_seccomp: configures current->seccomp.mode
+ * @seccomp_mode: requested mode to use
+ * @filter: optional struct sock_fprog for use with SECCOMP_MODE_FILTER
+ *
+ * Returns 0 on success or -EINVAL on failure.
+ */
+long prctl_set_seccomp(unsigned long seccomp_mode, void __user *filter)
+{
+	unsigned int op;
+	void __user *uargs;
+
+	switch (seccomp_mode) {
+	case SECCOMP_MODE_STRICT:
+		op = SECCOMP_SET_MODE_STRICT;
+		/*
+		 * Setting strict mode through prctl always ignored filter,
+		 * so make sure it is always NULL here to pass the internal
+		 * check in do_seccomp().
+		 */
+		uargs = NULL;
+		break;
+	case SECCOMP_MODE_FILTER:
+		op = SECCOMP_SET_MODE_FILTER;
+		uargs = filter;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	/* prctl interface doesn't have flags, so they are always zero. */
+	return do_seccomp(op, 0, uargs);
+}
+
+#if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE)
+static struct seccomp_filter *get_nth_filter(struct task_struct *task,
+					     unsigned long filter_off)
+{
+	struct seccomp_filter *orig, *filter;
+	unsigned long count;
+
+	/*
+	 * Note: this is only correct because the caller should be the (ptrace)
+	 * tracer of the task, otherwise lock_task_sighand is needed.
+	 */
+	spin_lock_irq(&task->sighand->siglock);
+
+	if (task->seccomp.mode != SECCOMP_MODE_FILTER) {
+		spin_unlock_irq(&task->sighand->siglock);
+		return ERR_PTR(-EINVAL);
+	}
+
+	orig = task->seccomp.filter;
+	__get_seccomp_filter(orig);
+	spin_unlock_irq(&task->sighand->siglock);
+
+	count = 0;
+	for (filter = orig; filter; filter = filter->prev)
+		count++;
+
+	if (filter_off >= count) {
+		filter = ERR_PTR(-ENOENT);
+		goto out;
+	}
+
+	count -= filter_off;
+	for (filter = orig; filter && count > 1; filter = filter->prev)
+		count--;
+
+	if (WARN_ON(count != 1 || !filter)) {
+		filter = ERR_PTR(-ENOENT);
+		goto out;
+	}
+
+	__get_seccomp_filter(filter);
+
+out:
+	__put_seccomp_filter(orig);
+	return filter;
+}
+
+long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
+			void __user *data)
+{
+	struct seccomp_filter *filter;
+	struct sock_fprog_kern *fprog;
+	long ret;
+
+	if (!capable(CAP_SYS_ADMIN) ||
+	    current->seccomp.mode != SECCOMP_MODE_DISABLED) {
+		return -EACCES;
+	}
+
+	filter = get_nth_filter(task, filter_off);
+	if (IS_ERR(filter))
+		return PTR_ERR(filter);
+
+	fprog = filter->prog->orig_prog;
+	if (!fprog) {
+		/* This must be a new non-cBPF filter, since we save
+		 * every cBPF filter's orig_prog above when
+		 * CONFIG_CHECKPOINT_RESTORE is enabled.
+		 */
+		ret = -EMEDIUMTYPE;
+		goto out;
+	}
+
+	ret = fprog->len;
+	if (!data)
+		goto out;
+
+	if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog)))
+		ret = -EFAULT;
+
+out:
+	__put_seccomp_filter(filter);
+	return ret;
+}
+
+long seccomp_get_metadata(struct task_struct *task,
+			  unsigned long size, void __user *data)
+{
+	long ret;
+	struct seccomp_filter *filter;
+	struct seccomp_metadata kmd = {};
+
+	if (!capable(CAP_SYS_ADMIN) ||
+	    current->seccomp.mode != SECCOMP_MODE_DISABLED) {
+		return -EACCES;
+	}
+
+	size = min_t(unsigned long, size, sizeof(kmd));
+
+	if (size < sizeof(kmd.filter_off))
+		return -EINVAL;
+
+	if (copy_from_user(&kmd.filter_off, data, sizeof(kmd.filter_off)))
+		return -EFAULT;
+
+	filter = get_nth_filter(task, kmd.filter_off);
+	if (IS_ERR(filter))
+		return PTR_ERR(filter);
+
+	if (filter->log)
+		kmd.flags |= SECCOMP_FILTER_FLAG_LOG;
+
+	ret = size;
+	if (copy_to_user(data, &kmd, size))
+		ret = -EFAULT;
+
+	__put_seccomp_filter(filter);
+	return ret;
+}
+#endif
+
+#ifdef CONFIG_SYSCTL
+
+/* Human readable action names for friendly sysctl interaction */
+#define SECCOMP_RET_KILL_PROCESS_NAME	"kill_process"
+#define SECCOMP_RET_KILL_THREAD_NAME	"kill_thread"
+#define SECCOMP_RET_TRAP_NAME		"trap"
+#define SECCOMP_RET_ERRNO_NAME		"errno"
+#define SECCOMP_RET_USER_NOTIF_NAME	"user_notif"
+#define SECCOMP_RET_TRACE_NAME		"trace"
+#define SECCOMP_RET_LOG_NAME		"log"
+#define SECCOMP_RET_ALLOW_NAME		"allow"
+
+static const char seccomp_actions_avail[] =
+				SECCOMP_RET_KILL_PROCESS_NAME	" "
+				SECCOMP_RET_KILL_THREAD_NAME	" "
+				SECCOMP_RET_TRAP_NAME		" "
+				SECCOMP_RET_ERRNO_NAME		" "
+				SECCOMP_RET_USER_NOTIF_NAME     " "
+				SECCOMP_RET_TRACE_NAME		" "
+				SECCOMP_RET_LOG_NAME		" "
+				SECCOMP_RET_ALLOW_NAME;
+
+struct seccomp_log_name {
+	u32		log;
+	const char	*name;
+};
+
+static const struct seccomp_log_name seccomp_log_names[] = {
+	{ SECCOMP_LOG_KILL_PROCESS, SECCOMP_RET_KILL_PROCESS_NAME },
+	{ SECCOMP_LOG_KILL_THREAD, SECCOMP_RET_KILL_THREAD_NAME },
+	{ SECCOMP_LOG_TRAP, SECCOMP_RET_TRAP_NAME },
+	{ SECCOMP_LOG_ERRNO, SECCOMP_RET_ERRNO_NAME },
+	{ SECCOMP_LOG_USER_NOTIF, SECCOMP_RET_USER_NOTIF_NAME },
+	{ SECCOMP_LOG_TRACE, SECCOMP_RET_TRACE_NAME },
+	{ SECCOMP_LOG_LOG, SECCOMP_RET_LOG_NAME },
+	{ SECCOMP_LOG_ALLOW, SECCOMP_RET_ALLOW_NAME },
+	{ }
+};
+
+static bool seccomp_names_from_actions_logged(char *names, size_t size,
+					      u32 actions_logged,
+					      const char *sep)
+{
+	const struct seccomp_log_name *cur;
+	bool append_sep = false;
+
+	for (cur = seccomp_log_names; cur->name && size; cur++) {
+		ssize_t ret;
+
+		if (!(actions_logged & cur->log))
+			continue;
+
+		if (append_sep) {
+			ret = strscpy(names, sep, size);
+			if (ret < 0)
+				return false;
+
+			names += ret;
+			size -= ret;
+		} else
+			append_sep = true;
+
+		ret = strscpy(names, cur->name, size);
+		if (ret < 0)
+			return false;
+
+		names += ret;
+		size -= ret;
+	}
+
+	return true;
+}
+
+static bool seccomp_action_logged_from_name(u32 *action_logged,
+					    const char *name)
+{
+	const struct seccomp_log_name *cur;
+
+	for (cur = seccomp_log_names; cur->name; cur++) {
+		if (!strcmp(cur->name, name)) {
+			*action_logged = cur->log;
+			return true;
+		}
+	}
+
+	return false;
+}
+
+static bool seccomp_actions_logged_from_names(u32 *actions_logged, char *names)
+{
+	char *name;
+
+	*actions_logged = 0;
+	while ((name = strsep(&names, " ")) && *name) {
+		u32 action_logged = 0;
+
+		if (!seccomp_action_logged_from_name(&action_logged, name))
+			return false;
+
+		*actions_logged |= action_logged;
+	}
+
+	return true;
+}
+
+static int read_actions_logged(struct ctl_table *ro_table, void __user *buffer,
+			       size_t *lenp, loff_t *ppos)
+{
+	char names[sizeof(seccomp_actions_avail)];
+	struct ctl_table table;
+
+	memset(names, 0, sizeof(names));
+
+	if (!seccomp_names_from_actions_logged(names, sizeof(names),
+					       seccomp_actions_logged, " "))
+		return -EINVAL;
+
+	table = *ro_table;
+	table.data = names;
+	table.maxlen = sizeof(names);
+	return proc_dostring(&table, 0, buffer, lenp, ppos);
+}
+
+static int write_actions_logged(struct ctl_table *ro_table, void __user *buffer,
+				size_t *lenp, loff_t *ppos, u32 *actions_logged)
+{
+	char names[sizeof(seccomp_actions_avail)];
+	struct ctl_table table;
+	int ret;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	memset(names, 0, sizeof(names));
+
+	table = *ro_table;
+	table.data = names;
+	table.maxlen = sizeof(names);
+	ret = proc_dostring(&table, 1, buffer, lenp, ppos);
+	if (ret)
+		return ret;
+
+	if (!seccomp_actions_logged_from_names(actions_logged, table.data))
+		return -EINVAL;
+
+	if (*actions_logged & SECCOMP_LOG_ALLOW)
+		return -EINVAL;
+
+	seccomp_actions_logged = *actions_logged;
+	return 0;
+}
+
+static void audit_actions_logged(u32 actions_logged, u32 old_actions_logged,
+				 int ret)
+{
+	char names[sizeof(seccomp_actions_avail)];
+	char old_names[sizeof(seccomp_actions_avail)];
+	const char *new = names;
+	const char *old = old_names;
+
+	if (!audit_enabled)
+		return;
+
+	memset(names, 0, sizeof(names));
+	memset(old_names, 0, sizeof(old_names));
+
+	if (ret)
+		new = "?";
+	else if (!actions_logged)
+		new = "(none)";
+	else if (!seccomp_names_from_actions_logged(names, sizeof(names),
+						    actions_logged, ","))
+		new = "?";
+
+	if (!old_actions_logged)
+		old = "(none)";
+	else if (!seccomp_names_from_actions_logged(old_names,
+						    sizeof(old_names),
+						    old_actions_logged, ","))
+		old = "?";
+
+	return audit_seccomp_actions_logged(new, old, !ret);
+}
+
+static int seccomp_actions_logged_handler(struct ctl_table *ro_table, int write,
+					  void *buffer, size_t *lenp,
+					  loff_t *ppos)
+{
+	int ret;
+
+	if (write) {
+		u32 actions_logged = 0;
+		u32 old_actions_logged = seccomp_actions_logged;
+
+		ret = write_actions_logged(ro_table, buffer, lenp, ppos,
+					   &actions_logged);
+		audit_actions_logged(actions_logged, old_actions_logged, ret);
+	} else
+		ret = read_actions_logged(ro_table, buffer, lenp, ppos);
+
+	return ret;
+}
+
+static struct ctl_path seccomp_sysctl_path[] = {
+	{ .procname = "kernel", },
+	{ .procname = "seccomp", },
+	{ }
+};
+
+static struct ctl_table seccomp_sysctl_table[] = {
+	{
+		.procname	= "actions_avail",
+		.data		= (void *) &seccomp_actions_avail,
+		.maxlen		= sizeof(seccomp_actions_avail),
+		.mode		= 0444,
+		.proc_handler	= proc_dostring,
+	},
+	{
+		.procname	= "actions_logged",
+		.mode		= 0644,
+		.proc_handler	= seccomp_actions_logged_handler,
+	},
+	{ }
+};
+
+static int __init seccomp_sysctl_init(void)
+{
+	struct ctl_table_header *hdr;
+
+	hdr = register_sysctl_paths(seccomp_sysctl_path, seccomp_sysctl_table);
+	if (!hdr)
+		pr_warn("sysctl registration failed\n");
+	else
+		kmemleak_not_leak(hdr);
+
+	return 0;
+}
+
+device_initcall(seccomp_sysctl_init)
+
+#endif /* CONFIG_SYSCTL */