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linux-sg2042/kernel/seccomp.c

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// SPDX-License-Identifier: GPL-2.0
/*
* linux/kernel/seccomp.c
*
* Copyright 2004-2005 Andrea Arcangeli <andrea@cpushare.com>
*
* Copyright (C) 2012 Google, Inc.
* Will Drewry <wad@chromium.org>
*
* This defines a simple but solid secure-computing facility.
*
* Mode 1 uses a fixed list of allowed system calls.
* Mode 2 allows user-defined system call filters in the form
* of Berkeley Packet Filters/Linux Socket Filters.
*/
#define pr_fmt(fmt) "seccomp: " fmt
#include <linux/refcount.h>
#include <linux/audit.h>
#include <linux/compat.h>
#include <linux/coredump.h>
#include <linux/kmemleak.h>
#include <linux/nospec.h>
#include <linux/prctl.h>
#include <linux/sched.h>
#include <linux/sched/task_stack.h>
#include <linux/seccomp.h>
#include <linux/slab.h>
#include <linux/syscalls.h>
#include <linux/sysctl.h>
#ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
#include <asm/syscall.h>
#endif
#ifdef CONFIG_SECCOMP_FILTER
#include <linux/file.h>
#include <linux/filter.h>
#include <linux/pid.h>
#include <linux/ptrace.h>
#include <linux/capability.h>
#include <linux/tracehook.h>
#include <linux/uaccess.h>
#include <linux/anon_inodes.h>
#include <linux/lockdep.h>
/*
* When SECCOMP_IOCTL_NOTIF_ID_VALID was first introduced, it had the
* wrong direction flag in the ioctl number. This is the broken one,
* which the kernel needs to keep supporting until all userspaces stop
* using the wrong command number.
*/
#define SECCOMP_IOCTL_NOTIF_ID_VALID_WRONG_DIR SECCOMP_IOR(2, __u64)
enum notify_state {
SECCOMP_NOTIFY_INIT,
SECCOMP_NOTIFY_SENT,
SECCOMP_NOTIFY_REPLIED,
};
struct seccomp_knotif {
/* The struct pid of the task whose filter triggered the notification */
struct task_struct *task;
/* The "cookie" for this request; this is unique for this filter. */
u64 id;
/*
* The seccomp data. This pointer is valid the entire time this
* notification is active, since it comes from __seccomp_filter which
* eclipses the entire lifecycle here.
*/
const struct seccomp_data *data;
/*
* Notification states. When SECCOMP_RET_USER_NOTIF is returned, a
* struct seccomp_knotif is created and starts out in INIT. Once the
* handler reads the notification off of an FD, it transitions to SENT.
* If a signal is received the state transitions back to INIT and
* another message is sent. When the userspace handler replies, state
* transitions to REPLIED.
*/
enum notify_state state;
/* The return values, only valid when in SECCOMP_NOTIFY_REPLIED */
int error;
long val;
u32 flags;
/*
* Signals when this has changed states, such as the listener
* dying, a new seccomp addfd message, or changing to REPLIED
*/
struct completion ready;
struct list_head list;
/* outstanding addfd requests */
struct list_head addfd;
};
/**
* struct seccomp_kaddfd - container for seccomp_addfd ioctl messages
*
* @file: A reference to the file to install in the other task
* @fd: The fd number to install it at. If the fd number is -1, it means the
* installing process should allocate the fd as normal.
* @flags: The flags for the new file descriptor. At the moment, only O_CLOEXEC
* is allowed.
* @ioctl_flags: The flags used for the seccomp_addfd ioctl.
* @ret: The return value of the installing process. It is set to the fd num
* upon success (>= 0).
* @completion: Indicates that the installing process has completed fd
* installation, or gone away (either due to successful
* reply, or signal)
*
*/
struct seccomp_kaddfd {
struct file *file;
int fd;
unsigned int flags;
__u32 ioctl_flags;
union {
bool setfd;
/* To only be set on reply */
int ret;
};
struct completion completion;
struct list_head list;
};
/**
* struct notification - container for seccomp userspace notifications. Since
* most seccomp filters will not have notification listeners attached and this
* structure is fairly large, we store the notification-specific stuff in a
* separate structure.
*
* @request: A semaphore that users of this notification can wait on for
* changes. Actual reads and writes are still controlled with
* filter->notify_lock.
* @next_id: The id of the next request.
* @notifications: A list of struct seccomp_knotif elements.
*/
struct notification {
struct semaphore request;
u64 next_id;
struct list_head notifications;
};
#ifdef SECCOMP_ARCH_NATIVE
/**
* struct action_cache - per-filter cache of seccomp actions per
* arch/syscall pair
*
* @allow_native: A bitmap where each bit represents whether the
* filter will always allow the syscall, for the
* native architecture.
* @allow_compat: A bitmap where each bit represents whether the
* filter will always allow the syscall, for the
* compat architecture.
*/
struct action_cache {
DECLARE_BITMAP(allow_native, SECCOMP_ARCH_NATIVE_NR);
#ifdef SECCOMP_ARCH_COMPAT
DECLARE_BITMAP(allow_compat, SECCOMP_ARCH_COMPAT_NR);
#endif
};
#else
struct action_cache { };
static inline bool seccomp_cache_check_allow(const struct seccomp_filter *sfilter,
const struct seccomp_data *sd)
{
return false;
}
static inline void seccomp_cache_prepare(struct seccomp_filter *sfilter)
{
}
#endif /* SECCOMP_ARCH_NATIVE */
/**
* struct seccomp_filter - container for seccomp BPF programs
*
* @refs: Reference count to manage the object lifetime.
* A filter's reference count is incremented for each directly
* attached task, once for the dependent filter, and if
* requested for the user notifier. When @refs reaches zero,
* the filter can be freed.
* @users: A filter's @users count is incremented for each directly
* attached task (filter installation, fork(), thread_sync),
* and once for the dependent filter (tracked in filter->prev).
* When it reaches zero it indicates that no direct or indirect
* users of that filter exist. No new tasks can get associated with
* this filter after reaching 0. The @users count is always smaller
* or equal to @refs. Hence, reaching 0 for @users does not mean
* the filter can be freed.
* @cache: cache of arch/syscall mappings to actions
* @log: true if all actions except for SECCOMP_RET_ALLOW should be logged
* @prev: points to a previously installed, or inherited, filter
* @prog: the BPF program to evaluate
* @notif: the struct that holds all notification related information
* @notify_lock: A lock for all notification-related accesses.
* @wqh: A wait queue for poll if a notifier is in use.
*
* seccomp_filter objects are organized in a tree linked via the @prev
* pointer. For any task, it appears to be a singly-linked list starting
* with current->seccomp.filter, the most recently attached or inherited filter.
* However, multiple filters may share a @prev node, by way of fork(), which
* results in a unidirectional tree existing in memory. This is similar to
* how namespaces work.
*
* seccomp_filter objects should never be modified after being attached
* to a task_struct (other than @refs).
*/
struct seccomp_filter {
refcount_t refs;
refcount_t users;
bool log;
struct action_cache cache;
struct seccomp_filter *prev;
struct bpf_prog *prog;
struct notification *notif;
struct mutex notify_lock;
wait_queue_head_t wqh;
};
/* Limit any path through the tree to 256KB worth of instructions. */
#define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter))
/*
* Endianness is explicitly ignored and left for BPF program authors to manage
* as per the specific architecture.
*/
static void populate_seccomp_data(struct seccomp_data *sd)
{
/*
* Instead of using current_pt_reg(), we're already doing the work
* to safely fetch "current", so just use "task" everywhere below.
*/
struct task_struct *task = current;
struct pt_regs *regs = task_pt_regs(task);
unsigned long args[6];
sd->nr = syscall_get_nr(task, regs);
sd->arch = syscall_get_arch(task);
syscall_get_arguments(task, regs, args);
sd->args[0] = args[0];
sd->args[1] = args[1];
sd->args[2] = args[2];
sd->args[3] = args[3];
sd->args[4] = args[4];
sd->args[5] = args[5];
sd->instruction_pointer = KSTK_EIP(task);
}
/**
* seccomp_check_filter - verify seccomp filter code
* @filter: filter to verify
* @flen: length of filter
*
* Takes a previously checked filter (by bpf_check_classic) and
* redirects all filter code that loads struct sk_buff data
* and related data through seccomp_bpf_load. It also
* enforces length and alignment checking of those loads.
*
* Returns 0 if the rule set is legal or -EINVAL if not.
*/
static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen)
{
int pc;
for (pc = 0; pc < flen; pc++) {
struct sock_filter *ftest = &filter[pc];
u16 code = ftest->code;
u32 k = ftest->k;
switch (code) {
case BPF_LD | BPF_W | BPF_ABS:
ftest->code = BPF_LDX | BPF_W | BPF_ABS;
/* 32-bit aligned and not out of bounds. */
if (k >= sizeof(struct seccomp_data) || k & 3)
return -EINVAL;
continue;
case BPF_LD | BPF_W | BPF_LEN:
ftest->code = BPF_LD | BPF_IMM;
ftest->k = sizeof(struct seccomp_data);
continue;
case BPF_LDX | BPF_W | BPF_LEN:
ftest->code = BPF_LDX | BPF_IMM;
ftest->k = sizeof(struct seccomp_data);
continue;
/* Explicitly include allowed calls. */
case BPF_RET | BPF_K:
case BPF_RET | BPF_A:
case BPF_ALU | BPF_ADD | BPF_K:
case BPF_ALU | BPF_ADD | BPF_X:
case BPF_ALU | BPF_SUB | BPF_K:
case BPF_ALU | BPF_SUB | BPF_X:
case BPF_ALU | BPF_MUL | BPF_K:
case BPF_ALU | BPF_MUL | BPF_X:
case BPF_ALU | BPF_DIV | BPF_K:
case BPF_ALU | BPF_DIV | BPF_X:
case BPF_ALU | BPF_AND | BPF_K:
case BPF_ALU | BPF_AND | BPF_X:
case BPF_ALU | BPF_OR | BPF_K:
case BPF_ALU | BPF_OR | BPF_X:
case BPF_ALU | BPF_XOR | BPF_K:
case BPF_ALU | BPF_XOR | BPF_X:
case BPF_ALU | BPF_LSH | BPF_K:
case BPF_ALU | BPF_LSH | BPF_X:
case BPF_ALU | BPF_RSH | BPF_K:
case BPF_ALU | BPF_RSH | BPF_X:
case BPF_ALU | BPF_NEG:
case BPF_LD | BPF_IMM:
case BPF_LDX | BPF_IMM:
case BPF_MISC | BPF_TAX:
case BPF_MISC | BPF_TXA:
case BPF_LD | BPF_MEM:
case BPF_LDX | BPF_MEM:
case BPF_ST:
case BPF_STX:
case BPF_JMP | BPF_JA:
case BPF_JMP | BPF_JEQ | BPF_K:
case BPF_JMP | BPF_JEQ | BPF_X:
case BPF_JMP | BPF_JGE | BPF_K:
case BPF_JMP | BPF_JGE | BPF_X:
case BPF_JMP | BPF_JGT | BPF_K:
case BPF_JMP | BPF_JGT | BPF_X:
case BPF_JMP | BPF_JSET | BPF_K:
case BPF_JMP | BPF_JSET | BPF_X:
continue;
default:
return -EINVAL;
}
}
return 0;
}
#ifdef SECCOMP_ARCH_NATIVE
static inline bool seccomp_cache_check_allow_bitmap(const void *bitmap,
size_t bitmap_size,
int syscall_nr)
{
if (unlikely(syscall_nr < 0 || syscall_nr >= bitmap_size))
return false;
syscall_nr = array_index_nospec(syscall_nr, bitmap_size);
return test_bit(syscall_nr, bitmap);
}
/**
* seccomp_cache_check_allow - lookup seccomp cache
* @sfilter: The seccomp filter
* @sd: The seccomp data to lookup the cache with
*
* Returns true if the seccomp_data is cached and allowed.
*/
static inline bool seccomp_cache_check_allow(const struct seccomp_filter *sfilter,
const struct seccomp_data *sd)
{
int syscall_nr = sd->nr;
const struct action_cache *cache = &sfilter->cache;
#ifndef SECCOMP_ARCH_COMPAT
/* A native-only architecture doesn't need to check sd->arch. */
return seccomp_cache_check_allow_bitmap(cache->allow_native,
SECCOMP_ARCH_NATIVE_NR,
syscall_nr);
#else
if (likely(sd->arch == SECCOMP_ARCH_NATIVE))
return seccomp_cache_check_allow_bitmap(cache->allow_native,
SECCOMP_ARCH_NATIVE_NR,
syscall_nr);
if (likely(sd->arch == SECCOMP_ARCH_COMPAT))
return seccomp_cache_check_allow_bitmap(cache->allow_compat,
SECCOMP_ARCH_COMPAT_NR,
syscall_nr);
#endif /* SECCOMP_ARCH_COMPAT */
WARN_ON_ONCE(true);
return false;
}
#endif /* SECCOMP_ARCH_NATIVE */
/**
* 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;
if (seccomp_cache_check_allow(f, sd))
return SECCOMP_RET_ALLOW;
/*
* 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 SYSCALL_WORK_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_task_syscall_work(task, SECCOMP);
}
#ifdef CONFIG_SECCOMP_FILTER
/* Returns 1 if the parent is an ancestor of the child. */
static int is_ancestor(struct seccomp_filter *parent,
struct seccomp_filter *child)
{
/* NULL is the root ancestor. */
if (parent == NULL)
return 1;
for (; child; child = child->prev)
if (child == parent)
return 1;
return 0;
}
/**
* seccomp_can_sync_threads: checks if all threads can be synchronized
*
* Expects sighand and cred_guard_mutex locks to be held.
*
* Returns 0 on success, -ve on error, or the pid of a thread which was
* either not in the correct seccomp mode or did not have an ancestral
* seccomp filter.
*/
static inline pid_t seccomp_can_sync_threads(void)
{
struct task_struct *thread, *caller;
BUG_ON(!mutex_is_locked(&current->signal->cred_guard_mutex));
assert_spin_locked(&current->sighand->siglock);
/* Validate all threads being eligible for synchronization. */
caller = current;
for_each_thread(caller, thread) {
pid_t failed;
/* Skip current, since it is initiating the sync. */
if (thread == caller)
continue;
if (thread->seccomp.mode == SECCOMP_MODE_DISABLED ||
(thread->seccomp.mode == SECCOMP_MODE_FILTER &&
is_ancestor(thread->seccomp.filter,
caller->seccomp.filter)))
continue;
/* Return the first thread that cannot be synchronized. */
failed = task_pid_vnr(thread);
/* If the pid cannot be resolved, then return -ESRCH */
if (WARN_ON(failed == 0))
failed = -ESRCH;
return failed;
}
return 0;
}
static inline void seccomp_filter_free(struct seccomp_filter *filter)
{
if (filter) {
bpf_prog_destroy(filter->prog);
kfree(filter);
}
}
static void __seccomp_filter_orphan(struct seccomp_filter *orig)
{
while (orig && refcount_dec_and_test(&orig->users)) {
if (waitqueue_active(&orig->wqh))
wake_up_poll(&orig->wqh, EPOLLHUP);
orig = orig->prev;
}
}
static void __put_seccomp_filter(struct seccomp_filter *orig)
{
/* Clean up single-reference branches iteratively. */
while (orig && refcount_dec_and_test(&orig->refs)) {
struct seccomp_filter *freeme = orig;
orig = orig->prev;
seccomp_filter_free(freeme);
}
}
static void __seccomp_filter_release(struct seccomp_filter *orig)
{
/* Notify about any unused filters in the task's former filter tree. */
__seccomp_filter_orphan(orig);
/* Finally drop all references to the task's former tree. */
__put_seccomp_filter(orig);
}
/**
* seccomp_filter_release - Detach the task from its filter tree,
* drop its reference count, and notify
* about unused filters
*
* This function should only be called when the task is exiting as
* it detaches it from its filter tree. As such, READ_ONCE() and
* barriers are not needed here, as would normally be needed.
*/
void seccomp_filter_release(struct task_struct *tsk)
{
struct seccomp_filter *orig = tsk->seccomp.filter;
/* We are effectively holding the siglock by not having any sighand. */
WARN_ON(tsk->sighand != NULL);
/* Detach task from its filter tree. */
tsk->seccomp.filter = NULL;
__seccomp_filter_release(orig);
}
/**
* seccomp_sync_threads: sets all threads to use current's filter
*
* Expects sighand and cred_guard_mutex locks to be held, and for
* seccomp_can_sync_threads() to have returned success already
* without dropping the locks.
*
*/
static inline void seccomp_sync_threads(unsigned long flags)
{
struct task_struct *thread, *caller;
BUG_ON(!mutex_is_locked(&current->signal->cred_guard_mutex));
assert_spin_locked(&current->sighand->siglock);
/* Synchronize all threads. */
caller = current;
for_each_thread(caller, thread) {
/* Skip current, since it needs no changes. */
if (thread == caller)
continue;
/* Get a task reference for the new leaf node. */
get_seccomp_filter(caller);
/*
* Drop the task reference to the shared ancestor since
* current's path will hold a reference. (This also
* allows a put before the assignment.)
*/
__seccomp_filter_release(thread->seccomp.filter);
/* Make our new filter tree visible. */
smp_store_release(&thread->seccomp.filter,
caller->seccomp.filter);
atomic_set(&thread->seccomp.filter_count,
atomic_read(&caller->seccomp.filter_count));
/*
* Don't let an unprivileged task work around
* the no_new_privs restriction by creating
* a thread that sets it up, enters seccomp,
* then dies.
*/
if (task_no_new_privs(caller))
task_set_no_new_privs(thread);
/*
* Opt the other thread into seccomp if needed.
* As threads are considered to be trust-realm
* equivalent (see ptrace_may_access), it is safe to
* allow one thread to transition the other.
*/
if (thread->seccomp.mode == SECCOMP_MODE_DISABLED)
seccomp_assign_mode(thread, SECCOMP_MODE_FILTER,
flags);
}
}
/**
* seccomp_prepare_filter: Prepares a seccomp filter for use.
* @fprog: BPF program to install
*
* Returns filter on success or an ERR_PTR on failure.
*/
static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog)
{
struct seccomp_filter *sfilter;
int ret;
const bool save_orig =
#if defined(CONFIG_CHECKPOINT_RESTORE) || defined(SECCOMP_ARCH_NATIVE)
true;
#else
false;
#endif
if (fprog->len == 0 || fprog->len > BPF_MAXINSNS)
return ERR_PTR(-EINVAL);
BUG_ON(INT_MAX / fprog->len < sizeof(struct sock_filter));
/*
* Installing a seccomp filter requires that the task has
* CAP_SYS_ADMIN in its namespace or be running with no_new_privs.
* This avoids scenarios where unprivileged tasks can affect the
* behavior of privileged children.
*/
if (!task_no_new_privs(current) &&
!ns_capable_noaudit(current_user_ns(), CAP_SYS_ADMIN))
return ERR_PTR(-EACCES);
/* Allocate a new seccomp_filter */
sfilter = kzalloc(sizeof(*sfilter), GFP_KERNEL | __GFP_NOWARN);
if (!sfilter)
return ERR_PTR(-ENOMEM);
mutex_init(&sfilter->notify_lock);
ret = bpf_prog_create_from_user(&sfilter->prog, fprog,
seccomp_check_filter, save_orig);
if (ret < 0) {
kfree(sfilter);
return ERR_PTR(ret);
}
refcount_set(&sfilter->refs, 1);
refcount_set(&sfilter->users, 1);
init_waitqueue_head(&sfilter->wqh);
return sfilter;
}
/**
* seccomp_prepare_user_filter - prepares a user-supplied sock_fprog
* @user_filter: pointer to the user data containing a sock_fprog.
*
* Returns 0 on success and non-zero otherwise.
*/
static struct seccomp_filter *
seccomp_prepare_user_filter(const char __user *user_filter)
{
struct sock_fprog fprog;
struct seccomp_filter *filter = ERR_PTR(-EFAULT);
#ifdef CONFIG_COMPAT
if (in_compat_syscall()) {
struct compat_sock_fprog fprog32;
if (copy_from_user(&fprog32, user_filter, sizeof(fprog32)))
goto out;
fprog.len = fprog32.len;
fprog.filter = compat_ptr(fprog32.filter);
} else /* falls through to the if below. */
#endif
if (copy_from_user(&fprog, user_filter, sizeof(fprog)))
goto out;
filter = seccomp_prepare_filter(&fprog);
out:
return filter;
}
#ifdef SECCOMP_ARCH_NATIVE
/**
* seccomp_is_const_allow - check if filter is constant allow with given data
* @fprog: The BPF programs
* @sd: The seccomp data to check against, only syscall number and arch
* number are considered constant.
*/
static bool seccomp_is_const_allow(struct sock_fprog_kern *fprog,
struct seccomp_data *sd)
{
unsigned int reg_value = 0;
unsigned int pc;
bool op_res;
if (WARN_ON_ONCE(!fprog))
return false;
for (pc = 0; pc < fprog->len; pc++) {
struct sock_filter *insn = &fprog->filter[pc];
u16 code = insn->code;
u32 k = insn->k;
switch (code) {
case BPF_LD | BPF_W | BPF_ABS:
switch (k) {
case offsetof(struct seccomp_data, nr):
reg_value = sd->nr;
break;
case offsetof(struct seccomp_data, arch):
reg_value = sd->arch;
break;
default:
/* can't optimize (non-constant value load) */
return false;
}
break;
case BPF_RET | BPF_K:
/* reached return with constant values only, check allow */
return k == SECCOMP_RET_ALLOW;
case BPF_JMP | BPF_JA:
pc += insn->k;
break;
case BPF_JMP | BPF_JEQ | BPF_K:
case BPF_JMP | BPF_JGE | BPF_K:
case BPF_JMP | BPF_JGT | BPF_K:
case BPF_JMP | BPF_JSET | BPF_K:
switch (BPF_OP(code)) {
case BPF_JEQ:
op_res = reg_value == k;
break;
case BPF_JGE:
op_res = reg_value >= k;
break;
case BPF_JGT:
op_res = reg_value > k;
break;
case BPF_JSET:
op_res = !!(reg_value & k);
break;
default:
/* can't optimize (unknown jump) */
return false;
}
pc += op_res ? insn->jt : insn->jf;
break;
case BPF_ALU | BPF_AND | BPF_K:
reg_value &= k;
break;
default:
/* can't optimize (unknown insn) */
return false;
}
}
/* ran off the end of the filter?! */
WARN_ON(1);
return false;
}
static void seccomp_cache_prepare_bitmap(struct seccomp_filter *sfilter,
void *bitmap, const void *bitmap_prev,
size_t bitmap_size, int arch)
{
struct sock_fprog_kern *fprog = sfilter->prog->orig_prog;
struct seccomp_data sd;
int nr;
if (bitmap_prev) {
/* The new filter must be as restrictive as the last. */
bitmap_copy(bitmap, bitmap_prev, bitmap_size);
} else {
/* Before any filters, all syscalls are always allowed. */
bitmap_fill(bitmap, bitmap_size);
}
for (nr = 0; nr < bitmap_size; nr++) {
/* No bitmap change: not a cacheable action. */
if (!test_bit(nr, bitmap))
continue;
sd.nr = nr;
sd.arch = arch;
/* No bitmap change: continue to always allow. */
if (seccomp_is_const_allow(fprog, &sd))
continue;
/*
* Not a cacheable action: always run filters.
* atomic clear_bit() not needed, filter not visible yet.
*/
__clear_bit(nr, bitmap);
}
}
/**
* seccomp_cache_prepare - emulate the filter to find cacheable syscalls
* @sfilter: The seccomp filter
*
* Returns 0 if successful or -errno if error occurred.
*/
static void seccomp_cache_prepare(struct seccomp_filter *sfilter)
{
struct action_cache *cache = &sfilter->cache;
const struct action_cache *cache_prev =
sfilter->prev ? &sfilter->prev->cache : NULL;
seccomp_cache_prepare_bitmap(sfilter, cache->allow_native,
cache_prev ? cache_prev->allow_native : NULL,
SECCOMP_ARCH_NATIVE_NR,
SECCOMP_ARCH_NATIVE);
#ifdef SECCOMP_ARCH_COMPAT
seccomp_cache_prepare_bitmap(sfilter, cache->allow_compat,
cache_prev ? cache_prev->allow_compat : NULL,
SECCOMP_ARCH_COMPAT_NR,
SECCOMP_ARCH_COMPAT);
#endif /* SECCOMP_ARCH_COMPAT */
}
#endif /* SECCOMP_ARCH_NATIVE */
/**
* 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;
seccomp_cache_prepare(filter);
current->seccomp.filter = filter;
atomic_inc(&current->seccomp.filter_count);
/* Now that the new filter is in place, synchronize to all threads. */
if (flags & SECCOMP_FILTER_FLAG_TSYNC)
seccomp_sync_threads(flags);
return 0;
}
static void __get_seccomp_filter(struct seccomp_filter *filter)
{
refcount_inc(&filter->refs);
}
/* get_seccomp_filter - increments the reference count of the filter on @tsk */
void get_seccomp_filter(struct task_struct *tsk)
{
struct seccomp_filter *orig = tsk->seccomp.filter;
if (!orig)
return;
__get_seccomp_filter(orig);
refcount_inc(&orig->users);
}
#endif /* CONFIG_SECCOMP_FILTER */
/* For use with seccomp_actions_logged */
#define SECCOMP_LOG_KILL_PROCESS (1 << 0)
#define SECCOMP_LOG_KILL_THREAD (1 << 1)
#define SECCOMP_LOG_TRAP (1 << 2)
#define SECCOMP_LOG_ERRNO (1 << 3)
#define SECCOMP_LOG_TRACE (1 << 4)
#define SECCOMP_LOG_LOG (1 << 5)
#define SECCOMP_LOG_ALLOW (1 << 6)
#define SECCOMP_LOG_USER_NOTIF (1 << 7)
static u32 seccomp_actions_logged = SECCOMP_LOG_KILL_PROCESS |
SECCOMP_LOG_KILL_THREAD |
SECCOMP_LOG_TRAP |
SECCOMP_LOG_ERRNO |
SECCOMP_LOG_USER_NOTIF |
SECCOMP_LOG_TRACE |
SECCOMP_LOG_LOG;
static inline void seccomp_log(unsigned long syscall, long signr, u32 action,
bool requested)
{
bool log = false;
switch (action) {
case SECCOMP_RET_ALLOW:
break;
case SECCOMP_RET_TRAP:
log = requested && seccomp_actions_logged & SECCOMP_LOG_TRAP;
break;
case SECCOMP_RET_ERRNO:
log = requested && seccomp_actions_logged & SECCOMP_LOG_ERRNO;
break;
case SECCOMP_RET_TRACE:
log = requested && seccomp_actions_logged & SECCOMP_LOG_TRACE;
break;
case SECCOMP_RET_USER_NOTIF:
log = requested && seccomp_actions_logged & SECCOMP_LOG_USER_NOTIF;
break;
case SECCOMP_RET_LOG:
log = seccomp_actions_logged & SECCOMP_LOG_LOG;
break;
case SECCOMP_RET_KILL_THREAD:
log = seccomp_actions_logged & SECCOMP_LOG_KILL_THREAD;
break;
case SECCOMP_RET_KILL_PROCESS:
default:
log = seccomp_actions_logged & SECCOMP_LOG_KILL_PROCESS;
}
/*
* Emit an audit message when the action is RET_KILL_*, RET_LOG, or the
* FILTER_FLAG_LOG bit was set. The admin has the ability to silence
* any action from being logged by removing the action name from the
* seccomp_actions_logged sysctl.
*/
if (!log)
return;
audit_seccomp(syscall, signr, action);
}
/*
* Secure computing mode 1 allows only read/write/exit/sigreturn.
* To be fully secure this must be combined with rlimit
* to limit the stack allocations too.
*/
static const int mode1_syscalls[] = {
__NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn,
-1, /* negative terminated */
};
static void __secure_computing_strict(int this_syscall)
{
const int *allowed_syscalls = mode1_syscalls;
#ifdef CONFIG_COMPAT
if (in_compat_syscall())
allowed_syscalls = get_compat_mode1_syscalls();
#endif
do {
if (*allowed_syscalls == this_syscall)
return;
} while (*++allowed_syscalls != -1);
#ifdef SECCOMP_DEBUG
dump_stack();
#endif
seccomp_log(this_syscall, SIGKILL, SECCOMP_RET_KILL_THREAD, true);
do_exit(SIGKILL);
}
#ifndef CONFIG_HAVE_ARCH_SECCOMP_FILTER
void secure_computing_strict(int this_syscall)
{
int mode = current->seccomp.mode;
if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
unlikely(current->ptrace & PT_SUSPEND_SECCOMP))
return;
if (mode == SECCOMP_MODE_DISABLED)
return;
else if (mode == SECCOMP_MODE_STRICT)
__secure_computing_strict(this_syscall);
else
BUG();
}
#else
#ifdef CONFIG_SECCOMP_FILTER
static u64 seccomp_next_notify_id(struct seccomp_filter *filter)
{
/*
* Note: overflow is ok here, the id just needs to be unique per
* filter.
*/
lockdep_assert_held(&filter->notify_lock);
return filter->notif->next_id++;
}
static void seccomp_handle_addfd(struct seccomp_kaddfd *addfd, struct seccomp_knotif *n)
{
int fd;
/*
* Remove the notification, and reset the list pointers, indicating
* that it has been handled.
*/
list_del_init(&addfd->list);
if (!addfd->setfd)
fd = receive_fd(addfd->file, addfd->flags);
else
fd = receive_fd_replace(addfd->fd, addfd->file, addfd->flags);
addfd->ret = fd;
if (addfd->ioctl_flags & SECCOMP_ADDFD_FLAG_SEND) {
/* If we fail reset and return an error to the notifier */
if (fd < 0) {
n->state = SECCOMP_NOTIFY_SENT;
} else {
/* Return the FD we just added */
n->flags = 0;
n->error = 0;
n->val = fd;
}
}
/*
* Mark the notification as completed. From this point, addfd mem
* might be invalidated and we can't safely read it anymore.
*/
complete(&addfd->completion);
}
static int seccomp_do_user_notification(int this_syscall,
struct seccomp_filter *match,
const struct seccomp_data *sd)
{
int err;
u32 flags = 0;
long ret = 0;
struct seccomp_knotif n = {};
struct seccomp_kaddfd *addfd, *tmp;
mutex_lock(&match->notify_lock);
err = -ENOSYS;
if (!match->notif)
goto out;
n.task = current;
n.state = SECCOMP_NOTIFY_INIT;
n.data = sd;
n.id = seccomp_next_notify_id(match);
init_completion(&n.ready);
list_add(&n.list, &match->notif->notifications);
INIT_LIST_HEAD(&n.addfd);
up(&match->notif->request);
wake_up_poll(&match->wqh, EPOLLIN | EPOLLRDNORM);
/*
* This is where we wait for a reply from userspace.
*/
do {
mutex_unlock(&match->notify_lock);
err = wait_for_completion_interruptible(&n.ready);
mutex_lock(&match->notify_lock);
if (err != 0)
goto interrupted;
addfd = list_first_entry_or_null(&n.addfd,
struct seccomp_kaddfd, list);
/* Check if we were woken up by a addfd message */
if (addfd)
seccomp_handle_addfd(addfd, &n);
} while (n.state != SECCOMP_NOTIFY_REPLIED);
ret = n.val;
err = n.error;
flags = n.flags;
interrupted:
/* If there were any pending addfd calls, clear them out */
list_for_each_entry_safe(addfd, tmp, &n.addfd, list) {
/* The process went away before we got a chance to handle it */
addfd->ret = -ESRCH;
list_del_init(&addfd->list);
complete(&addfd->completion);
}
/*
* Note that it's possible the listener died in between the time when
* we were notified of a response (or a signal) and when we were able to
* re-acquire the lock, so only delete from the list if the
* notification actually exists.
*
* Also note that this test is only valid because there's no way to
* *reattach* to a notifier right now. If one is added, we'll need to
* keep track of the notif itself and make sure they match here.
*/
if (match->notif)
list_del(&n.list);
out:
mutex_unlock(&match->notify_lock);
/* Userspace requests to continue the syscall. */
if (flags & SECCOMP_USER_NOTIF_FLAG_CONTINUE)
return 0;
syscall_set_return_value(current, current_pt_regs(),
err, ret);
return -1;
}
static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
const bool recheck_after_trace)
{
u32 filter_ret, action;
struct seccomp_filter *match = NULL;
int data;
struct seccomp_data sd_local;
/*
* Make sure that any changes to mode from another thread have
* been seen after SYSCALL_WORK_SECCOMP was seen.
*/
smp_rmb();
if (!sd) {
populate_seccomp_data(&sd_local);
sd = &sd_local;
}
filter_ret = seccomp_run_filters(sd, &match);
data = filter_ret & SECCOMP_RET_DATA;
action = filter_ret & SECCOMP_RET_ACTION_FULL;
switch (action) {
case SECCOMP_RET_ERRNO:
/* Set low-order bits as an errno, capped at MAX_ERRNO. */
if (data > MAX_ERRNO)
data = MAX_ERRNO;
syscall_set_return_value(current, current_pt_regs(),
-data, 0);
goto skip;
case SECCOMP_RET_TRAP:
/* Show the handler the original registers. */
syscall_rollback(current, current_pt_regs());
/* Let the filter pass back 16 bits of data. */
force_sig_seccomp(this_syscall, data, false);
goto skip;
case SECCOMP_RET_TRACE:
/* We've been put in this state by the ptracer already. */
if (recheck_after_trace)
return 0;
/* ENOSYS these calls if there is no tracer attached. */
if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) {
syscall_set_return_value(current,
current_pt_regs(),
-ENOSYS, 0);
goto skip;
}
/* Allow the BPF to provide the event message */
ptrace_event(PTRACE_EVENT_SECCOMP, data);
/*
* The delivery of a fatal signal during event
* notification may silently skip tracer notification,
* which could leave us with a potentially unmodified
* syscall that the tracer would have liked to have
* changed. Since the process is about to die, we just
* force the syscall to be skipped and let the signal
* kill the process and correctly handle any tracer exit
* notifications.
*/
if (fatal_signal_pending(current))
goto skip;
/* Check if the tracer forced the syscall to be skipped. */
this_syscall = syscall_get_nr(current, current_pt_regs());
if (this_syscall < 0)
goto skip;
/*
* Recheck the syscall, since it may have changed. This
* intentionally uses a NULL struct seccomp_data to force
* a reload of all registers. This does not goto skip since
* a skip would have already been reported.
*/
if (__seccomp_filter(this_syscall, NULL, true))
return -1;
return 0;
case SECCOMP_RET_USER_NOTIF:
if (seccomp_do_user_notification(this_syscall, match, sd))
goto skip;
return 0;
case SECCOMP_RET_LOG:
seccomp_log(this_syscall, 0, action, true);
return 0;
case SECCOMP_RET_ALLOW:
/*
* Note that the "match" filter will always be NULL for
* this action since SECCOMP_RET_ALLOW is the starting
* state in seccomp_run_filters().
*/
return 0;
case SECCOMP_RET_KILL_THREAD:
case SECCOMP_RET_KILL_PROCESS:
default:
seccomp_log(this_syscall, SIGSYS, action, true);
/* Dump core only if this is the last remaining thread. */
if (action != SECCOMP_RET_KILL_THREAD ||
(atomic_read(&current->signal->live) == 1)) {
/* Show the original registers in the dump. */
syscall_rollback(current, current_pt_regs());
/* Trigger a coredump with SIGSYS */
force_sig_seccomp(this_syscall, data, true);
} else {
do_exit(SIGSYS);
}
return -1; /* skip the syscall go directly to signal handling */
}
unreachable();
skip:
seccomp_log(this_syscall, 0, action, match ? match->log : false);
return -1;
}
#else
static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
const bool recheck_after_trace)
{
BUG();
return -1;
}
#endif
int __secure_computing(const struct seccomp_data *sd)
{
int mode = current->seccomp.mode;
int this_syscall;
if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
unlikely(current->ptrace & PT_SUSPEND_SECCOMP))
return 0;
this_syscall = sd ? sd->nr :
syscall_get_nr(current, current_pt_regs());
switch (mode) {
case SECCOMP_MODE_STRICT:
__secure_computing_strict(this_syscall); /* may call do_exit */
return 0;
case SECCOMP_MODE_FILTER:
return __seccomp_filter(this_syscall, sd, false);
default:
BUG();
}
}
#endif /* CONFIG_HAVE_ARCH_SECCOMP_FILTER */
long prctl_get_seccomp(void)
{
return current->seccomp.mode;
}
/**
* seccomp_set_mode_strict: internal function for setting strict seccomp
*
* Once current->seccomp.mode is non-zero, it may not be changed.
*
* Returns 0 on success or -EINVAL on failure.
*/
static long seccomp_set_mode_strict(void)
{
const unsigned long seccomp_mode = SECCOMP_MODE_STRICT;
long ret = -EINVAL;
spin_lock_irq(&current->sighand->siglock);
if (!seccomp_may_assign_mode(seccomp_mode))
goto out;
#ifdef TIF_NOTSC
disable_TSC();
#endif
seccomp_assign_mode(current, seccomp_mode, 0);
ret = 0;
out:
spin_unlock_irq(&current->sighand->siglock);
return ret;
}
#ifdef CONFIG_SECCOMP_FILTER
static void seccomp_notify_free(struct seccomp_filter *filter)
{
kfree(filter->notif);
filter->notif = NULL;
}
static void seccomp_notify_detach(struct seccomp_filter *filter)
{
struct seccomp_knotif *knotif;
if (!filter)
return;
mutex_lock(&filter->notify_lock);
/*
* If this file is being closed because e.g. the task who owned it
* died, let's wake everyone up who was waiting on us.
*/
list_for_each_entry(knotif, &filter->notif->notifications, list) {
if (knotif->state == SECCOMP_NOTIFY_REPLIED)
continue;
knotif->state = SECCOMP_NOTIFY_REPLIED;
knotif->error = -ENOSYS;
knotif->val = 0;
/*
* We do not need to wake up any pending addfd messages, as
* the notifier will do that for us, as this just looks
* like a standard reply.
*/
complete(&knotif->ready);
}
seccomp_notify_free(filter);
mutex_unlock(&filter->notify_lock);
}
static int seccomp_notify_release(struct inode *inode, struct file *file)
{
struct seccomp_filter *filter = file->private_data;
seccomp_notify_detach(filter);
__put_seccomp_filter(filter);
return 0;
}
/* must be called with notif_lock held */
static inline struct seccomp_knotif *
find_notification(struct seccomp_filter *filter, u64 id)
{
struct seccomp_knotif *cur;
lockdep_assert_held(&filter->notify_lock);
list_for_each_entry(cur, &filter->notif->notifications, list) {
if (cur->id == id)
return cur;
}
return NULL;
}
static long seccomp_notify_recv(struct seccomp_filter *filter,
void __user *buf)
{
struct seccomp_knotif *knotif = NULL, *cur;
struct seccomp_notif unotif;
ssize_t ret;
/* Verify that we're not given garbage to keep struct extensible. */
ret = check_zeroed_user(buf, sizeof(unotif));
if (ret < 0)
return ret;
if (!ret)
return -EINVAL;
memset(&unotif, 0, sizeof(unotif));
ret = down_interruptible(&filter->notif->request);
if (ret < 0)
return ret;
mutex_lock(&filter->notify_lock);
list_for_each_entry(cur, &filter->notif->notifications, list) {
if (cur->state == SECCOMP_NOTIFY_INIT) {
knotif = cur;
break;
}
}
/*
* If we didn't find a notification, it could be that the task was
* interrupted by a fatal signal between the time we were woken and
* when we were able to acquire the rw lock.
*/
if (!knotif) {
ret = -ENOENT;
goto out;
}
unotif.id = knotif->id;
unotif.pid = task_pid_vnr(knotif->task);
unotif.data = *(knotif->data);
knotif->state = SECCOMP_NOTIFY_SENT;
wake_up_poll(&filter->wqh, EPOLLOUT | EPOLLWRNORM);
ret = 0;
out:
mutex_unlock(&filter->notify_lock);
if (ret == 0 && copy_to_user(buf, &unotif, sizeof(unotif))) {
ret = -EFAULT;
/*
* Userspace screwed up. To make sure that we keep this
* notification alive, let's reset it back to INIT. It
* may have died when we released the lock, so we need to make
* sure it's still around.
*/
mutex_lock(&filter->notify_lock);
knotif = find_notification(filter, unotif.id);
if (knotif) {
knotif->state = SECCOMP_NOTIFY_INIT;
up(&filter->notif->request);
}
mutex_unlock(&filter->notify_lock);
}
return ret;
}
static long seccomp_notify_send(struct seccomp_filter *filter,
void __user *buf)
{
struct seccomp_notif_resp resp = {};
struct seccomp_knotif *knotif;
long ret;
if (copy_from_user(&resp, buf, sizeof(resp)))
return -EFAULT;
if (resp.flags & ~SECCOMP_USER_NOTIF_FLAG_CONTINUE)
return -EINVAL;
if ((resp.flags & SECCOMP_USER_NOTIF_FLAG_CONTINUE) &&
(resp.error || resp.val))
return -EINVAL;
ret = mutex_lock_interruptible(&filter->notify_lock);
if (ret < 0)
return ret;
knotif = find_notification(filter, resp.id);
if (!knotif) {
ret = -ENOENT;
goto out;
}
/* Allow exactly one reply. */
if (knotif->state != SECCOMP_NOTIFY_SENT) {
ret = -EINPROGRESS;
goto out;
}
ret = 0;
knotif->state = SECCOMP_NOTIFY_REPLIED;
knotif->error = resp.error;
knotif->val = resp.val;
knotif->flags = resp.flags;
complete(&knotif->ready);
out:
mutex_unlock(&filter->notify_lock);
return ret;
}
static long seccomp_notify_id_valid(struct seccomp_filter *filter,
void __user *buf)
{
struct seccomp_knotif *knotif;
u64 id;
long ret;
if (copy_from_user(&id, buf, sizeof(id)))
return -EFAULT;
ret = mutex_lock_interruptible(&filter->notify_lock);
if (ret < 0)
return ret;
knotif = find_notification(filter, id);
if (knotif && knotif->state == SECCOMP_NOTIFY_SENT)
ret = 0;
else
ret = -ENOENT;
mutex_unlock(&filter->notify_lock);
return ret;
}
static long seccomp_notify_addfd(struct seccomp_filter *filter,
struct seccomp_notif_addfd __user *uaddfd,
unsigned int size)
{
struct seccomp_notif_addfd addfd;
struct seccomp_knotif *knotif;
struct seccomp_kaddfd kaddfd;
int ret;
BUILD_BUG_ON(sizeof(addfd) < SECCOMP_NOTIFY_ADDFD_SIZE_VER0);
BUILD_BUG_ON(sizeof(addfd) != SECCOMP_NOTIFY_ADDFD_SIZE_LATEST);
if (size < SECCOMP_NOTIFY_ADDFD_SIZE_VER0 || size >= PAGE_SIZE)
return -EINVAL;
ret = copy_struct_from_user(&addfd, sizeof(addfd), uaddfd, size);
if (ret)
return ret;
if (addfd.newfd_flags & ~O_CLOEXEC)
return -EINVAL;
if (addfd.flags & ~(SECCOMP_ADDFD_FLAG_SETFD | SECCOMP_ADDFD_FLAG_SEND))
return -EINVAL;
if (addfd.newfd && !(addfd.flags & SECCOMP_ADDFD_FLAG_SETFD))
return -EINVAL;
kaddfd.file = fget(addfd.srcfd);
if (!kaddfd.file)
return -EBADF;
kaddfd.ioctl_flags = addfd.flags;
kaddfd.flags = addfd.newfd_flags;
kaddfd.setfd = addfd.flags & SECCOMP_ADDFD_FLAG_SETFD;
kaddfd.fd = addfd.newfd;
init_completion(&kaddfd.completion);
ret = mutex_lock_interruptible(&filter->notify_lock);
if (ret < 0)
goto out;
knotif = find_notification(filter, addfd.id);
if (!knotif) {
ret = -ENOENT;
goto out_unlock;
}
/*
* We do not want to allow for FD injection to occur before the
* notification has been picked up by a userspace handler, or after
* the notification has been replied to.
*/
if (knotif->state != SECCOMP_NOTIFY_SENT) {
ret = -EINPROGRESS;
goto out_unlock;
}
if (addfd.flags & SECCOMP_ADDFD_FLAG_SEND) {
/*
* Disallow queuing an atomic addfd + send reply while there are
* some addfd requests still to process.
*
* There is no clear reason to support it and allows us to keep
* the loop on the other side straight-forward.
*/
if (!list_empty(&knotif->addfd)) {
ret = -EBUSY;
goto out_unlock;
}
/* Allow exactly only one reply */
knotif->state = SECCOMP_NOTIFY_REPLIED;
}
list_add(&kaddfd.list, &knotif->addfd);
complete(&knotif->ready);
mutex_unlock(&filter->notify_lock);
/* Now we wait for it to be processed or be interrupted */
ret = wait_for_completion_interruptible(&kaddfd.completion);
if (ret == 0) {
/*
* We had a successful completion. The other side has already
* removed us from the addfd queue, and
* wait_for_completion_interruptible has a memory barrier upon
* success that lets us read this value directly without
* locking.
*/
ret = kaddfd.ret;
goto out;
}
mutex_lock(&filter->notify_lock);
/*
* Even though we were woken up by a signal and not a successful
* completion, a completion may have happened in the mean time.
*
* We need to check again if the addfd request has been handled,
* and if not, we will remove it from the queue.
*/
if (list_empty(&kaddfd.list))
ret = kaddfd.ret;
else
list_del(&kaddfd.list);
out_unlock:
mutex_unlock(&filter->notify_lock);
out:
fput(kaddfd.file);
return ret;
}
static long seccomp_notify_ioctl(struct file *file, unsigned int cmd,
unsigned long arg)
{
struct seccomp_filter *filter = file->private_data;
void __user *buf = (void __user *)arg;
/* Fixed-size ioctls */
switch (cmd) {
case SECCOMP_IOCTL_NOTIF_RECV:
return seccomp_notify_recv(filter, buf);
case SECCOMP_IOCTL_NOTIF_SEND:
return seccomp_notify_send(filter, buf);
case SECCOMP_IOCTL_NOTIF_ID_VALID_WRONG_DIR:
case SECCOMP_IOCTL_NOTIF_ID_VALID:
return seccomp_notify_id_valid(filter, buf);
}
/* Extensible Argument ioctls */
#define EA_IOCTL(cmd) ((cmd) & ~(IOC_INOUT | IOCSIZE_MASK))
switch (EA_IOCTL(cmd)) {
case EA_IOCTL(SECCOMP_IOCTL_NOTIF_ADDFD):
return seccomp_notify_addfd(filter, buf, _IOC_SIZE(cmd));
default:
return -EINVAL;
}
}
static __poll_t seccomp_notify_poll(struct file *file,
struct poll_table_struct *poll_tab)
{
struct seccomp_filter *filter = file->private_data;
__poll_t ret = 0;
struct seccomp_knotif *cur;
poll_wait(file, &filter->wqh, poll_tab);
if (mutex_lock_interruptible(&filter->notify_lock) < 0)
return EPOLLERR;
list_for_each_entry(cur, &filter->notif->notifications, list) {
if (cur->state == SECCOMP_NOTIFY_INIT)
ret |= EPOLLIN | EPOLLRDNORM;
if (cur->state == SECCOMP_NOTIFY_SENT)
ret |= EPOLLOUT | EPOLLWRNORM;
if ((ret & EPOLLIN) && (ret & EPOLLOUT))
break;
}
mutex_unlock(&filter->notify_lock);
if (refcount_read(&filter->users) == 0)
ret |= EPOLLHUP;
return ret;
}
static const struct file_operations seccomp_notify_ops = {
.poll = seccomp_notify_poll,
.release = seccomp_notify_release,
.unlocked_ioctl = seccomp_notify_ioctl,
.compat_ioctl = seccomp_notify_ioctl,
};
static struct file *init_listener(struct seccomp_filter *filter)
{
struct file *ret;
ret = ERR_PTR(-ENOMEM);
filter->notif = kzalloc(sizeof(*(filter->notif)), GFP_KERNEL);
if (!filter->notif)
goto out;
sema_init(&filter->notif->request, 0);
filter->notif->next_id = get_random_u64();
INIT_LIST_HEAD(&filter->notif->notifications);
ret = anon_inode_getfile("seccomp notify", &seccomp_notify_ops,
filter, O_RDWR);
if (IS_ERR(ret))
goto out_notif;
/* The file has a reference to it now */
__get_seccomp_filter(filter);
out_notif:
if (IS_ERR(ret))
seccomp_notify_free(filter);
out:
return ret;
}
/*
* Does @new_child have a listener while an ancestor also has a listener?
* If so, we'll want to reject this filter.
* This only has to be tested for the current process, even in the TSYNC case,
* because TSYNC installs @child with the same parent on all threads.
* Note that @new_child is not hooked up to its parent at this point yet, so
* we use current->seccomp.filter.
*/
static bool has_duplicate_listener(struct seccomp_filter *new_child)
{
struct seccomp_filter *cur;
/* must be protected against concurrent TSYNC */
lockdep_assert_held(&current->sighand->siglock);
if (!new_child->notif)
return false;
for (cur = current->seccomp.filter; cur; cur = cur->prev) {
if (cur->notif)
return true;
}
return false;
}
/**
* seccomp_set_mode_filter: internal function for setting seccomp filter
* @flags: flags to change filter behavior
* @filter: struct sock_fprog containing filter
*
* This function may be called repeatedly to install additional filters.
* Every filter successfully installed will be evaluated (in reverse order)
* for each system call the task makes.
*
* Once current->seccomp.mode is non-zero, it may not be changed.
*
* Returns 0 on success or -EINVAL on failure.
*/
static long seccomp_set_mode_filter(unsigned int flags,
const char __user *filter)
{
const unsigned long seccomp_mode = SECCOMP_MODE_FILTER;
struct seccomp_filter *prepared = NULL;
long ret = -EINVAL;
int listener = -1;
struct file *listener_f = NULL;
/* Validate flags. */
if (flags & ~SECCOMP_FILTER_FLAG_MASK)
return -EINVAL;
/*
* In the successful case, NEW_LISTENER returns the new listener fd.
* But in the failure case, TSYNC returns the thread that died. If you
* combine these two flags, there's no way to tell whether something
* succeeded or failed. So, let's disallow this combination if the user
* has not explicitly requested no errors from TSYNC.
*/
if ((flags & SECCOMP_FILTER_FLAG_TSYNC) &&
(flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) &&
((flags & SECCOMP_FILTER_FLAG_TSYNC_ESRCH) == 0))
return -EINVAL;
/* Prepare the new filter before holding any locks. */
prepared = seccomp_prepare_user_filter(filter);
if (IS_ERR(prepared))
return PTR_ERR(prepared);
if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) {
listener = get_unused_fd_flags(O_CLOEXEC);
if (listener < 0) {
ret = listener;
goto out_free;
}
listener_f = init_listener(prepared);
if (IS_ERR(listener_f)) {
put_unused_fd(listener);
ret = PTR_ERR(listener_f);
goto out_free;
}
}
/*
* Make sure we cannot change seccomp or nnp state via TSYNC
* while another thread is in the middle of calling exec.
*/
if (flags & SECCOMP_FILTER_FLAG_TSYNC &&
mutex_lock_killable(&current->signal->cred_guard_mutex))
goto out_put_fd;
spin_lock_irq(&current->sighand->siglock);
if (!seccomp_may_assign_mode(seccomp_mode))
goto out;
if (has_duplicate_listener(prepared)) {
ret = -EBUSY;
goto out;
}
ret = seccomp_attach_filter(flags, prepared);
if (ret)
goto out;
/* Do not free the successfully attached filter. */
prepared = NULL;
seccomp_assign_mode(current, seccomp_mode, flags);
out:
spin_unlock_irq(&current->sighand->siglock);
if (flags & SECCOMP_FILTER_FLAG_TSYNC)
mutex_unlock(&current->signal->cred_guard_mutex);
out_put_fd:
if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) {
if (ret) {
listener_f->private_data = NULL;
fput(listener_f);
put_unused_fd(listener);
seccomp_notify_detach(prepared);
} else {
fd_install(listener, listener_f);
ret = listener;
}
}
out_free:
seccomp_filter_free(prepared);
return ret;
}
#else
static inline long seccomp_set_mode_filter(unsigned int flags,
const char __user *filter)
{
return -EINVAL;
}
#endif
static long seccomp_get_action_avail(const char __user *uaction)
{
u32 action;
if (copy_from_user(&action, uaction, sizeof(action)))
return -EFAULT;
switch (action) {
case SECCOMP_RET_KILL_PROCESS:
case SECCOMP_RET_KILL_THREAD:
case SECCOMP_RET_TRAP:
case SECCOMP_RET_ERRNO:
case SECCOMP_RET_USER_NOTIF:
case SECCOMP_RET_TRACE:
case SECCOMP_RET_LOG:
case SECCOMP_RET_ALLOW:
break;
default:
return -EOPNOTSUPP;
}
return 0;
}
static long seccomp_get_notif_sizes(void __user *usizes)
{
struct seccomp_notif_sizes sizes = {
.seccomp_notif = sizeof(struct seccomp_notif),
.seccomp_notif_resp = sizeof(struct seccomp_notif_resp),
.seccomp_data = sizeof(struct seccomp_data),
};
if (copy_to_user(usizes, &sizes, sizeof(sizes)))
return -EFAULT;
return 0;
}
/* Common entry point for both prctl and syscall. */
static long do_seccomp(unsigned int op, unsigned int flags,
void __user *uargs)
{
switch (op) {
case SECCOMP_SET_MODE_STRICT:
if (flags != 0 || uargs != NULL)
return -EINVAL;
return seccomp_set_mode_strict();
case SECCOMP_SET_MODE_FILTER:
return seccomp_set_mode_filter(flags, uargs);
case SECCOMP_GET_ACTION_AVAIL:
if (flags != 0)
return -EINVAL;
return seccomp_get_action_avail(uargs);
case SECCOMP_GET_NOTIF_SIZES:
if (flags != 0)
return -EINVAL;
return seccomp_get_notif_sizes(uargs);
default:
return -EINVAL;
}
}
SYSCALL_DEFINE3(seccomp, unsigned int, op, unsigned int, flags,
void __user *, uargs)
{
return do_seccomp(op, flags, uargs);
}
/**
* prctl_set_seccomp: configures current->seccomp.mode
* @seccomp_mode: requested mode to use
* @filter: optional struct sock_fprog for use with SECCOMP_MODE_FILTER
*
* Returns 0 on success or -EINVAL on failure.
*/
long prctl_set_seccomp(unsigned long seccomp_mode, void __user *filter)
{
unsigned int op;
void __user *uargs;
switch (seccomp_mode) {
case SECCOMP_MODE_STRICT:
op = SECCOMP_SET_MODE_STRICT;
/*
* Setting strict mode through prctl always ignored filter,
* so make sure it is always NULL here to pass the internal
* check in do_seccomp().
*/
uargs = NULL;
break;
case SECCOMP_MODE_FILTER:
op = SECCOMP_SET_MODE_FILTER;
uargs = filter;
break;
default:
return -EINVAL;
}
/* prctl interface doesn't have flags, so they are always zero. */
return do_seccomp(op, 0, uargs);
}
#if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE)
static struct seccomp_filter *get_nth_filter(struct task_struct *task,
unsigned long filter_off)
{
struct seccomp_filter *orig, *filter;
unsigned long count;
/*
* Note: this is only correct because the caller should be the (ptrace)
* tracer of the task, otherwise lock_task_sighand is needed.
*/
spin_lock_irq(&task->sighand->siglock);
if (task->seccomp.mode != SECCOMP_MODE_FILTER) {
spin_unlock_irq(&task->sighand->siglock);
return ERR_PTR(-EINVAL);
}
orig = task->seccomp.filter;
__get_seccomp_filter(orig);
spin_unlock_irq(&task->sighand->siglock);
count = 0;
for (filter = orig; filter; filter = filter->prev)
count++;
if (filter_off >= count) {
filter = ERR_PTR(-ENOENT);
goto out;
}
count -= filter_off;
for (filter = orig; filter && count > 1; filter = filter->prev)
count--;
if (WARN_ON(count != 1 || !filter)) {
filter = ERR_PTR(-ENOENT);
goto out;
}
__get_seccomp_filter(filter);
out:
__put_seccomp_filter(orig);
return filter;
}
long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
void __user *data)
{
struct seccomp_filter *filter;
struct sock_fprog_kern *fprog;
long ret;
if (!capable(CAP_SYS_ADMIN) ||
current->seccomp.mode != SECCOMP_MODE_DISABLED) {
return -EACCES;
}
filter = get_nth_filter(task, filter_off);
if (IS_ERR(filter))
return PTR_ERR(filter);
fprog = filter->prog->orig_prog;
if (!fprog) {
/* This must be a new non-cBPF filter, since we save
* every cBPF filter's orig_prog above when
* CONFIG_CHECKPOINT_RESTORE is enabled.
*/
ret = -EMEDIUMTYPE;
goto out;
}
ret = fprog->len;
if (!data)
goto out;
if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog)))
ret = -EFAULT;
out:
__put_seccomp_filter(filter);
return ret;
}
long seccomp_get_metadata(struct task_struct *task,
unsigned long size, void __user *data)
{
long ret;
struct seccomp_filter *filter;
struct seccomp_metadata kmd = {};
if (!capable(CAP_SYS_ADMIN) ||
current->seccomp.mode != SECCOMP_MODE_DISABLED) {
return -EACCES;
}
size = min_t(unsigned long, size, sizeof(kmd));
if (size < sizeof(kmd.filter_off))
return -EINVAL;
if (copy_from_user(&kmd.filter_off, data, sizeof(kmd.filter_off)))
return -EFAULT;
filter = get_nth_filter(task, kmd.filter_off);
if (IS_ERR(filter))
return PTR_ERR(filter);
if (filter->log)
kmd.flags |= SECCOMP_FILTER_FLAG_LOG;
ret = size;
if (copy_to_user(data, &kmd, size))
ret = -EFAULT;
__put_seccomp_filter(filter);
return ret;
}
#endif
#ifdef CONFIG_SYSCTL
/* Human readable action names for friendly sysctl interaction */
#define SECCOMP_RET_KILL_PROCESS_NAME "kill_process"
#define SECCOMP_RET_KILL_THREAD_NAME "kill_thread"
#define SECCOMP_RET_TRAP_NAME "trap"
#define SECCOMP_RET_ERRNO_NAME "errno"
#define SECCOMP_RET_USER_NOTIF_NAME "user_notif"
#define SECCOMP_RET_TRACE_NAME "trace"
#define SECCOMP_RET_LOG_NAME "log"
#define SECCOMP_RET_ALLOW_NAME "allow"
static const char seccomp_actions_avail[] =
SECCOMP_RET_KILL_PROCESS_NAME " "
SECCOMP_RET_KILL_THREAD_NAME " "
SECCOMP_RET_TRAP_NAME " "
SECCOMP_RET_ERRNO_NAME " "
SECCOMP_RET_USER_NOTIF_NAME " "
SECCOMP_RET_TRACE_NAME " "
SECCOMP_RET_LOG_NAME " "
SECCOMP_RET_ALLOW_NAME;
struct seccomp_log_name {
u32 log;
const char *name;
};
static const struct seccomp_log_name seccomp_log_names[] = {
{ SECCOMP_LOG_KILL_PROCESS, SECCOMP_RET_KILL_PROCESS_NAME },
{ SECCOMP_LOG_KILL_THREAD, SECCOMP_RET_KILL_THREAD_NAME },
{ SECCOMP_LOG_TRAP, SECCOMP_RET_TRAP_NAME },
{ SECCOMP_LOG_ERRNO, SECCOMP_RET_ERRNO_NAME },
{ SECCOMP_LOG_USER_NOTIF, SECCOMP_RET_USER_NOTIF_NAME },
{ SECCOMP_LOG_TRACE, SECCOMP_RET_TRACE_NAME },
{ SECCOMP_LOG_LOG, SECCOMP_RET_LOG_NAME },
{ SECCOMP_LOG_ALLOW, SECCOMP_RET_ALLOW_NAME },
{ }
};
static bool seccomp_names_from_actions_logged(char *names, size_t size,
u32 actions_logged,
const char *sep)
{
const struct seccomp_log_name *cur;
bool append_sep = false;
for (cur = seccomp_log_names; cur->name && size; cur++) {
ssize_t ret;
if (!(actions_logged & cur->log))
continue;
if (append_sep) {
ret = strscpy(names, sep, size);
if (ret < 0)
return false;
names += ret;
size -= ret;
} else
append_sep = true;
ret = strscpy(names, cur->name, size);
if (ret < 0)
return false;
names += ret;
size -= ret;
}
return true;
}
static bool seccomp_action_logged_from_name(u32 *action_logged,
const char *name)
{
const struct seccomp_log_name *cur;
for (cur = seccomp_log_names; cur->name; cur++) {
if (!strcmp(cur->name, name)) {
*action_logged = cur->log;
return true;
}
}
return false;
}
static bool seccomp_actions_logged_from_names(u32 *actions_logged, char *names)
{
char *name;
*actions_logged = 0;
while ((name = strsep(&names, " ")) && *name) {
u32 action_logged = 0;
if (!seccomp_action_logged_from_name(&action_logged, name))
return false;
*actions_logged |= action_logged;
}
return true;
}
static int read_actions_logged(struct ctl_table *ro_table, void *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 *buffer,
size_t *lenp, loff_t *ppos, u32 *actions_logged)
{
char names[sizeof(seccomp_actions_avail)];
struct ctl_table table;
int ret;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
memset(names, 0, sizeof(names));
table = *ro_table;
table.data = names;
table.maxlen = sizeof(names);
ret = proc_dostring(&table, 1, buffer, lenp, ppos);
if (ret)
return ret;
if (!seccomp_actions_logged_from_names(actions_logged, table.data))
return -EINVAL;
if (*actions_logged & SECCOMP_LOG_ALLOW)
return -EINVAL;
seccomp_actions_logged = *actions_logged;
return 0;
}
static void audit_actions_logged(u32 actions_logged, u32 old_actions_logged,
int ret)
{
char names[sizeof(seccomp_actions_avail)];
char old_names[sizeof(seccomp_actions_avail)];
const char *new = names;
const char *old = old_names;
if (!audit_enabled)
return;
memset(names, 0, sizeof(names));
memset(old_names, 0, sizeof(old_names));
if (ret)
new = "?";
else if (!actions_logged)
new = "(none)";
else if (!seccomp_names_from_actions_logged(names, sizeof(names),
actions_logged, ","))
new = "?";
if (!old_actions_logged)
old = "(none)";
else if (!seccomp_names_from_actions_logged(old_names,
sizeof(old_names),
old_actions_logged, ","))
old = "?";
return audit_seccomp_actions_logged(new, old, !ret);
}
static int seccomp_actions_logged_handler(struct ctl_table *ro_table, int write,
void *buffer, size_t *lenp,
loff_t *ppos)
{
int ret;
if (write) {
u32 actions_logged = 0;
u32 old_actions_logged = seccomp_actions_logged;
ret = write_actions_logged(ro_table, buffer, lenp, ppos,
&actions_logged);
audit_actions_logged(actions_logged, old_actions_logged, ret);
} else
ret = read_actions_logged(ro_table, buffer, lenp, ppos);
return ret;
}
static struct ctl_path seccomp_sysctl_path[] = {
{ .procname = "kernel", },
{ .procname = "seccomp", },
{ }
};
static struct ctl_table seccomp_sysctl_table[] = {
{
.procname = "actions_avail",
.data = (void *) &seccomp_actions_avail,
.maxlen = sizeof(seccomp_actions_avail),
.mode = 0444,
.proc_handler = proc_dostring,
},
{
.procname = "actions_logged",
.mode = 0644,
.proc_handler = seccomp_actions_logged_handler,
},
{ }
};
static int __init seccomp_sysctl_init(void)
{
struct ctl_table_header *hdr;
hdr = register_sysctl_paths(seccomp_sysctl_path, seccomp_sysctl_table);
if (!hdr)
pr_warn("sysctl registration failed\n");
else
kmemleak_not_leak(hdr);
return 0;
}
device_initcall(seccomp_sysctl_init)
#endif /* CONFIG_SYSCTL */
#ifdef CONFIG_SECCOMP_CACHE_DEBUG
/* Currently CONFIG_SECCOMP_CACHE_DEBUG implies SECCOMP_ARCH_NATIVE */
static void proc_pid_seccomp_cache_arch(struct seq_file *m, const char *name,
const void *bitmap, size_t bitmap_size)
{
int nr;
for (nr = 0; nr < bitmap_size; nr++) {
bool cached = test_bit(nr, bitmap);
char *status = cached ? "ALLOW" : "FILTER";
seq_printf(m, "%s %d %s\n", name, nr, status);
}
}
int proc_pid_seccomp_cache(struct seq_file *m, struct pid_namespace *ns,
struct pid *pid, struct task_struct *task)
{
struct seccomp_filter *f;
unsigned long flags;
/*
* We don't want some sandboxed process to know what their seccomp
* filters consist of.
*/
if (!file_ns_capable(m->file, &init_user_ns, CAP_SYS_ADMIN))
return -EACCES;
if (!lock_task_sighand(task, &flags))
return -ESRCH;
f = READ_ONCE(task->seccomp.filter);
if (!f) {
unlock_task_sighand(task, &flags);
return 0;
}
/* prevent filter from being freed while we are printing it */
__get_seccomp_filter(f);
unlock_task_sighand(task, &flags);
proc_pid_seccomp_cache_arch(m, SECCOMP_ARCH_NATIVE_NAME,
f->cache.allow_native,
SECCOMP_ARCH_NATIVE_NR);
#ifdef SECCOMP_ARCH_COMPAT
proc_pid_seccomp_cache_arch(m, SECCOMP_ARCH_COMPAT_NAME,
f->cache.allow_compat,
SECCOMP_ARCH_COMPAT_NR);
#endif /* SECCOMP_ARCH_COMPAT */
__put_seccomp_filter(f);
return 0;
}
#endif /* CONFIG_SECCOMP_CACHE_DEBUG */
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