text: // 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.
   */
  
  #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/security.h>
  #include <linux/tracehook.h>
  #include <linux/uaccess.h>
  #include <linux/anon_inodes.h>
  
  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;
  
  	/* Signals when this has entered SECCOMP_NOTIFY_REPLIED */
  	struct completion ready;
  
  	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.
   * @wqh: A wait queue for poll.
   */
  struct notification {
  	struct semaphore request;
  	u64 next_id;
  	struct list_head notifications;
  	wait_queue_head_t wqh;
  };
  
  /**
   * struct seccomp_filter - container for seccomp BPF programs
   *
   * @usage: reference count to manage the object lifetime.
   *         get/put helpers should be used when accessing an instance
   *         outside of a lifetime-guarded section.  In general, this
   *         is only needed for handling filters shared across tasks.
   * @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.
   *
   * 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 @usage).
   */
  struct seccomp_filter {
  	refcount_t usage;
  	bool log;
  	struct seccomp_filter *prev;
  	struct bpf_prog *prog;
  	struct notification *notif;
  	struct mutex notify_lock;
  };
  
  /* 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)
  {
  	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();
  	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).
  	 */
  	preempt_disable();
  	for (; f; f = f->prev) {
  		u32 cur_ret = BPF_PROG_RUN(f->prog, sd);
  
  		if (ACTION_ONLY(cur_ret) < ACTION_ONLY(ret)) {
  			ret = cur_ret;
  			*match = f;
  		}
  	}
  	preempt_enable();
  	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 it 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;
  }
  
  /**
   * 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.)
  		 */
  		put_seccomp_filter(thread);
  		smp_store_release(&thread->seccomp.filter,
  				  caller->seccomp.filter);
  
  		/*
  		 * 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) &&
  	    security_capable(current_cred(), current_user_ns(),
  				     CAP_SYS_ADMIN, CAP_OPT_NOAUDIT) != 0)
  		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->usage, 1);
  
  	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)
  			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;
  
  	/* 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->usage);
  }
  
  /* 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);
  }
  
  static inline void seccomp_filter_free(struct seccomp_filter *filter)
  {
  	if (filter) {
  		bpf_prog_destroy(filter->prog);
  		kfree(filter);
  	}
  }
  
  static void __put_seccomp_filter(struct seccomp_filter *orig)
  {
  	/* Clean up single-reference branches iteratively. */
  	while (orig && refcount_dec_and_test(&orig->usage)) {
  		struct seccomp_filter *freeme = orig;
  		orig = orig->prev;
  		seccomp_filter_free(freeme);
  	}
  }
  
  /* put_seccomp_filter - decrements the ref count of tsk->seccomp.filter */
  void put_seccomp_filter(struct task_struct *tsk)
  {
  	__put_seccomp_filter(tsk->seccomp.filter);
  }
  
  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();
  	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(SIGSYS, &info, current);
  }
  #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,
  	0, /* null terminated */
  };
  
  static void __secure_computing_strict(int this_syscall)
  {
  	const int *syscall_whitelist = mode1_syscalls;
  #ifdef CONFIG_COMPAT
  	if (in_compat_syscall())
  		syscall_whitelist = get_compat_mode1_syscalls();
  #endif
  	do {
  		if (*syscall_whitelist == this_syscall)
  			return;
  	} while (*++syscall_whitelist);
  
  #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_do_user_notification(int this_syscall,
  					 struct seccomp_filter *match,
  					 const struct seccomp_data *sd)
  {
  	int err;
  	long ret = 0;
  	struct seccomp_knotif n = {};
  
  	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);
  
  	up(&match->notif->request);
  	wake_up_poll(&match->notif->wqh, EPOLLIN | EPOLLRDNORM);
  	mutex_unlock(&match->notify_lock);
  
  	/*
  	 * This is where we wait for a reply from userspace.
  	 */
  	err = wait_for_completion_interruptible(&n.ready);
  	mutex_lock(&match->notify_lock);
  	if (err == 0) {
  		ret = n.val;
  		err = n.error;
  	}
  
  	/*
  	 * Note that it's possible the listener died in between the time when
  	 * we were notified of a respons (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);
  	syscall_set_return_value(current, task_pt_regs(current),
  				 err, ret);
  }
  
  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, task_pt_regs(current),
  					 -data, 0);
  		goto skip;
  
  	case SECCOMP_RET_TRAP:
  		/* Show the handler the original registers. */
  		syscall_rollback(current, task_pt_regs(current));
  		/* 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,
  						 task_pt_regs(current),
  						 -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, task_pt_regs(current));
  		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:
  		seccomp_do_user_notification(this_syscall, match, sd);
  		goto skip;
  
  	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_PROCESS ||
  		    get_nr_threads(current) == 1) {
  			kernel_siginfo_t info;
  
  			/* Show the original registers in the dump. */
  			syscall_rollback(current, task_pt_regs(current));
  			/* Trigger a manual coredump since do_exit skips it. */
  			seccomp_init_siginfo(&info, this_syscall, data);
  			do_coredump(&info);
  		}
  		if (action == SECCOMP_RET_KILL_PROCESS)
  			do_group_exit(SIGSYS);
  		else
  			do_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();
  }
  #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, task_pt_regs(current));
  
  	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 int seccomp_notify_release(struct inode *inode, struct file *file)
  {
  	struct seccomp_filter *filter = file->private_data;
  	struct seccomp_knotif *knotif;
  
  	if (!filter)
  		return 0;
  
  	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;
  
  		complete(&knotif->ready);
  	}
  
  	kfree(filter->notif);
  	filter->notif = NULL;
  	mutex_unlock(&filter->notify_lock);
  	__put_seccomp_filter(filter);
  	return 0;
  }
  
  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;
  
  	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->notif->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.
  		 */
  		knotif = NULL;
  		mutex_lock(&filter->notify_lock);
  		list_for_each_entry(cur, &filter->notif->notifications, list) {
  			if (cur->id == unotif.id) {
  				knotif = cur;
  				break;
  			}
  		}
  
  		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 = NULL, *cur;
  	long ret;
  
  	if (copy_from_user(&resp, buf, sizeof(resp)))
  		return -EFAULT;
  
  	if (resp.flags)
  		return -EINVAL;
  
  	ret = mutex_lock_interruptible(&filter->notify_lock);
  	if (ret < 0)
  		return ret;
  
  	list_for_each_entry(cur, &filter->notif->notifications, list) {
  		if (cur->id == resp.id) {
  			knotif = cur;
  			break;
  		}
  	}
  
  	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;
  	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 = NULL;
  	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;
  
  	ret = -ENOENT;
  	list_for_each_entry(knotif, &filter->notif->notifications, list) {
  		if (knotif->id == id) {
  			if (knotif->state == SECCOMP_NOTIFY_SENT)
  				ret = 0;
  			goto out;
  		}
  	}
  
  out:
  	mutex_unlock(&filter->notify_lock);
  	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;
  
  	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:
  		return seccomp_notify_id_valid(filter, buf);
  	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->notif->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);
  
  	return ret;
  }
  
  static const struct file_operations seccomp_notify_ops = {
  	.poll = seccomp_notify_poll,
  	.release = seccomp_notify_release,
  	.unlocked_ioctl = seccomp_notify_ioctl,
  };
  
  static struct file *init_listener(struct seccomp_filter *filter)
  {
  	struct file *ret = ERR_PTR(-EBUSY);
  	struct seccomp_filter *cur;
  
  	for (cur = current->seccomp.filter; cur; cur = cur->prev) {
  		if (cur->notif)
  			goto out;
  	}
  
  	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);
  	init_waitqueue_head(&filter->notif->wqh);
  
  	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))
  		kfree(filter->notif);
  out:
  	return ret;
  }
  
  /**
   * 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 ((flags & SECCOMP_FILTER_FLAG_TSYNC) &&
  	    (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER))
  		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;
  
  	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);
  		} 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 __user *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("seccomp: sysctl registration failed\n");
  	else
  		kmemleak_not_leak(hdr);
  
  	return 0;
  }
  
  device_initcall(seccomp_sysctl_init)
  
  #endif /* CONFIG_SYSCTL */
  