seccomp: rename "usage" to "refs" and document

[linux-block.git] / kernel / seccomp.c

// 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>
#include <linux/lockdep.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;
        u32 flags;

        /* 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
 *
 * @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.
 * @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 @refs).
 */
struct seccomp_filter {
        refcount_t refs;
        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(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;
}

/**
 * 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);
                atomic_set(&thread->seccomp.filter_count,
                           atomic_read(&thread->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) &&
            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->refs, 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) {
                        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);
}

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->refs)) {
                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(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,
        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 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 = {};

        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;
                flags = n.flags;
        }

        /*
         * 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);

        /* Userspace requests to continue the syscall. */
        if (flags & SECCOMP_USER_NOTIF_FLAG_CONTINUE)
                return 0;

        syscall_set_return_value(current, task_pt_regs(current),
                                 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, 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:
                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_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;
}

/* 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->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.
                 */
                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_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,
        .compat_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 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;

        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 *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 */