linux-stable/kernel/seccomp.c
Tycho Andersen f8e529ed94 seccomp, ptrace: add support for dumping seccomp filters
This patch adds support for dumping a process' (classic BPF) seccomp
filters via ptrace.

PTRACE_SECCOMP_GET_FILTER allows the tracer to dump the user's classic BPF
seccomp filters. addr should be an integer which represents the ith seccomp
filter (0 is the most recently installed filter). data should be a struct
sock_filter * with enough room for the ith filter, or NULL, in which case
the filter is not saved. The return value for this command is the number of
BPF instructions the program represents, or negative in the case of errors.
Command specific errors are ENOENT: which indicates that there is no ith
filter in this seccomp tree, and EMEDIUMTYPE, which indicates that the ith
filter was not installed as a classic BPF filter.

A caveat with this approach is that there is no way to get explicitly at
the heirarchy of seccomp filters, and users need to memcmp() filters to
decide which are inherited. This means that a task which installs two of
the same filter can potentially confuse users of this interface.

v2: * make save_orig const
    * check that the orig_prog exists (not necessary right now, but when
       grows eBPF support it will be)
    * s/n/filter_off and make it an unsigned long to match ptrace
    * count "down" the tree instead of "up" when passing a filter offset

v3: * don't take the current task's lock for inspecting its seccomp mode
    * use a 0x42** constant for the ptrace command value

v4: * don't copy to userspace while holding spinlocks

v5: * add another condition to WARN_ON

v6: * rebase on net-next

Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
Acked-by: Kees Cook <keescook@chromium.org>
CC: Will Drewry <wad@chromium.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
CC: Andy Lutomirski <luto@amacapital.net>
CC: Pavel Emelyanov <xemul@parallels.com>
CC: Serge E. Hallyn <serge.hallyn@ubuntu.com>
CC: Alexei Starovoitov <ast@kernel.org>
CC: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-10-27 19:55:13 -07:00

943 lines
25 KiB
C

/*
* 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/atomic.h>
#include <linux/audit.h>
#include <linux/compat.h>
#include <linux/sched.h>
#include <linux/seccomp.h>
#include <linux/slab.h>
#include <linux/syscalls.h>
#ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
#include <asm/syscall.h>
#endif
#ifdef CONFIG_SECCOMP_FILTER
#include <linux/filter.h>
#include <linux/pid.h>
#include <linux/ptrace.h>
#include <linux/security.h>
#include <linux/tracehook.h>
#include <linux/uaccess.h>
/**
* struct seccomp_filter - container for seccomp BPF programs
*
* @usage: reference count to manage the object lifetime.
* get/put helpers should be used when accessing an instance
* outside of a lifetime-guarded section. In general, this
* is only needed for handling filters shared across tasks.
* @prev: points to a previously installed, or inherited, filter
* @len: the number of instructions in the program
* @insnsi: the BPF program instructions to evaluate
*
* seccomp_filter objects are organized in a tree linked via the @prev
* pointer. For any task, it appears to be a singly-linked list starting
* with current->seccomp.filter, the most recently attached or inherited filter.
* However, multiple filters may share a @prev node, by way of fork(), which
* results in a unidirectional tree existing in memory. This is similar to
* how namespaces work.
*
* seccomp_filter objects should never be modified after being attached
* to a task_struct (other than @usage).
*/
struct seccomp_filter {
atomic_t usage;
struct seccomp_filter *prev;
struct bpf_prog *prog;
};
/* Limit any path through the tree to 256KB worth of instructions. */
#define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter))
/*
* Endianness is explicitly ignored and left for BPF program authors to manage
* as per the specific architecture.
*/
static void populate_seccomp_data(struct seccomp_data *sd)
{
struct task_struct *task = current;
struct pt_regs *regs = task_pt_regs(task);
unsigned long args[6];
sd->nr = syscall_get_nr(task, regs);
sd->arch = syscall_get_arch();
syscall_get_arguments(task, regs, 0, 6, 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 @syscall
* @syscall: number of the current system call
*
* Returns valid seccomp BPF response codes.
*/
static u32 seccomp_run_filters(struct seccomp_data *sd)
{
struct seccomp_data sd_local;
u32 ret = SECCOMP_RET_ALLOW;
/* Make sure cross-thread synced filter points somewhere sane. */
struct seccomp_filter *f =
lockless_dereference(current->seccomp.filter);
/* Ensure unexpected behavior doesn't result in failing open. */
if (unlikely(WARN_ON(f == NULL)))
return SECCOMP_RET_KILL;
if (!sd) {
populate_seccomp_data(&sd_local);
sd = &sd_local;
}
/*
* 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(f->prog, (void *)sd);
if ((cur_ret & SECCOMP_RET_ACTION) < (ret & SECCOMP_RET_ACTION))
ret = cur_ret;
}
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;
}
static inline void seccomp_assign_mode(struct task_struct *task,
unsigned long seccomp_mode)
{
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();
set_tsk_thread_flag(task, TIF_SECCOMP);
}
#ifdef CONFIG_SECCOMP_FILTER
/* Returns 1 if the parent is an ancestor of the child. */
static int is_ancestor(struct seccomp_filter *parent,
struct seccomp_filter *child)
{
/* NULL is the root ancestor. */
if (parent == NULL)
return 1;
for (; child; child = child->prev)
if (child == parent)
return 1;
return 0;
}
/**
* seccomp_can_sync_threads: checks if all threads can be synchronized
*
* Expects sighand and cred_guard_mutex locks to be held.
*
* Returns 0 on success, -ve on error, or the pid of a thread which was
* either not in the correct seccomp mode or it did not have an ancestral
* seccomp filter.
*/
static inline pid_t seccomp_can_sync_threads(void)
{
struct task_struct *thread, *caller;
BUG_ON(!mutex_is_locked(&current->signal->cred_guard_mutex));
assert_spin_locked(&current->sighand->siglock);
/* Validate all threads being eligible for synchronization. */
caller = current;
for_each_thread(caller, thread) {
pid_t failed;
/* Skip current, since it is initiating the sync. */
if (thread == caller)
continue;
if (thread->seccomp.mode == SECCOMP_MODE_DISABLED ||
(thread->seccomp.mode == SECCOMP_MODE_FILTER &&
is_ancestor(thread->seccomp.filter,
caller->seccomp.filter)))
continue;
/* Return the first thread that cannot be synchronized. */
failed = task_pid_vnr(thread);
/* If the pid cannot be resolved, then return -ESRCH */
if (unlikely(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(void)
{
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);
/*
* 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) {
/*
* 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);
seccomp_assign_mode(thread, SECCOMP_MODE_FILTER);
}
}
}
/**
* 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 = config_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_noaudit(current_cred(), current_user_ns(),
CAP_SYS_ADMIN) != 0)
return ERR_PTR(-EACCES);
/* Allocate a new seccomp_filter */
sfilter = kzalloc(sizeof(*sfilter), GFP_KERNEL | __GFP_NOWARN);
if (!sfilter)
return ERR_PTR(-ENOMEM);
ret = bpf_prog_create_from_user(&sfilter->prog, fprog,
seccomp_check_filter, save_orig);
if (ret < 0) {
kfree(sfilter);
return ERR_PTR(ret);
}
atomic_set(&sfilter->usage, 1);
return sfilter;
}
/**
* seccomp_prepare_user_filter - prepares a user-supplied sock_fprog
* @user_filter: pointer to the user data containing a sock_fprog.
*
* Returns 0 on success and non-zero otherwise.
*/
static struct seccomp_filter *
seccomp_prepare_user_filter(const char __user *user_filter)
{
struct sock_fprog fprog;
struct seccomp_filter *filter = ERR_PTR(-EFAULT);
#ifdef CONFIG_COMPAT
if (is_compat_task()) {
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.
*/
static long seccomp_attach_filter(unsigned int flags,
struct seccomp_filter *filter)
{
unsigned long total_insns;
struct seccomp_filter *walker;
assert_spin_locked(&current->sighand->siglock);
/* Validate resulting filter length. */
total_insns = filter->prog->len;
for (walker = current->seccomp.filter; walker; walker = walker->prev)
total_insns += walker->prog->len + 4; /* 4 instr penalty */
if (total_insns > MAX_INSNS_PER_PATH)
return -ENOMEM;
/* If thread sync has been requested, check that it is possible. */
if (flags & SECCOMP_FILTER_FLAG_TSYNC) {
int ret;
ret = seccomp_can_sync_threads();
if (ret)
return ret;
}
/*
* If there is an existing filter, make it the prev and don't drop its
* task reference.
*/
filter->prev = current->seccomp.filter;
current->seccomp.filter = filter;
/* Now that the new filter is in place, synchronize to all threads. */
if (flags & SECCOMP_FILTER_FLAG_TSYNC)
seccomp_sync_threads();
return 0;
}
/* 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;
/* Reference count is bounded by the number of total processes. */
atomic_inc(&orig->usage);
}
static inline void seccomp_filter_free(struct seccomp_filter *filter)
{
if (filter) {
bpf_prog_destroy(filter->prog);
kfree(filter);
}
}
/* put_seccomp_filter - decrements the ref count of tsk->seccomp.filter */
void put_seccomp_filter(struct task_struct *tsk)
{
struct seccomp_filter *orig = tsk->seccomp.filter;
/* Clean up single-reference branches iteratively. */
while (orig && atomic_dec_and_test(&orig->usage)) {
struct seccomp_filter *freeme = orig;
orig = orig->prev;
seccomp_filter_free(freeme);
}
}
/**
* 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 siginfo info;
memset(&info, 0, sizeof(info));
info.si_signo = SIGSYS;
info.si_code = SYS_SECCOMP;
info.si_call_addr = (void __user *)KSTK_EIP(current);
info.si_errno = reason;
info.si_arch = syscall_get_arch();
info.si_syscall = syscall;
force_sig_info(SIGSYS, &info, current);
}
#endif /* CONFIG_SECCOMP_FILTER */
/*
* 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 int mode1_syscalls[] = {
__NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn,
0, /* null terminated */
};
#ifdef CONFIG_COMPAT
static int mode1_syscalls_32[] = {
__NR_seccomp_read_32, __NR_seccomp_write_32, __NR_seccomp_exit_32, __NR_seccomp_sigreturn_32,
0, /* null terminated */
};
#endif
static void __secure_computing_strict(int this_syscall)
{
int *syscall_whitelist = mode1_syscalls;
#ifdef CONFIG_COMPAT
if (is_compat_task())
syscall_whitelist = mode1_syscalls_32;
#endif
do {
if (*syscall_whitelist == this_syscall)
return;
} while (*++syscall_whitelist);
#ifdef SECCOMP_DEBUG
dump_stack();
#endif
audit_seccomp(this_syscall, SIGKILL, SECCOMP_RET_KILL);
do_exit(SIGKILL);
}
#ifndef CONFIG_HAVE_ARCH_SECCOMP_FILTER
void secure_computing_strict(int this_syscall)
{
int mode = current->seccomp.mode;
if (config_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
int __secure_computing(void)
{
u32 phase1_result = seccomp_phase1(NULL);
if (likely(phase1_result == SECCOMP_PHASE1_OK))
return 0;
else if (likely(phase1_result == SECCOMP_PHASE1_SKIP))
return -1;
else
return seccomp_phase2(phase1_result);
}
#ifdef CONFIG_SECCOMP_FILTER
static u32 __seccomp_phase1_filter(int this_syscall, struct seccomp_data *sd)
{
u32 filter_ret, action;
int data;
/*
* Make sure that any changes to mode from another thread have
* been seen after TIF_SECCOMP was seen.
*/
rmb();
filter_ret = seccomp_run_filters(sd);
data = filter_ret & SECCOMP_RET_DATA;
action = filter_ret & SECCOMP_RET_ACTION;
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:
return filter_ret; /* Save the rest for phase 2. */
case SECCOMP_RET_ALLOW:
return SECCOMP_PHASE1_OK;
case SECCOMP_RET_KILL:
default:
audit_seccomp(this_syscall, SIGSYS, action);
do_exit(SIGSYS);
}
unreachable();
skip:
audit_seccomp(this_syscall, 0, action);
return SECCOMP_PHASE1_SKIP;
}
#endif
/**
* seccomp_phase1() - run fast path seccomp checks on the current syscall
* @arg sd: The seccomp_data or NULL
*
* This only reads pt_regs via the syscall_xyz helpers. The only change
* it will make to pt_regs is via syscall_set_return_value, and it will
* only do that if it returns SECCOMP_PHASE1_SKIP.
*
* If sd is provided, it will not read pt_regs at all.
*
* It may also call do_exit or force a signal; these actions must be
* safe.
*
* If it returns SECCOMP_PHASE1_OK, the syscall passes checks and should
* be processed normally.
*
* If it returns SECCOMP_PHASE1_SKIP, then the syscall should not be
* invoked. In this case, seccomp_phase1 will have set the return value
* using syscall_set_return_value.
*
* If it returns anything else, then the return value should be passed
* to seccomp_phase2 from a context in which ptrace hooks are safe.
*/
u32 seccomp_phase1(struct seccomp_data *sd)
{
int mode = current->seccomp.mode;
int this_syscall = sd ? sd->nr :
syscall_get_nr(current, task_pt_regs(current));
if (config_enabled(CONFIG_CHECKPOINT_RESTORE) &&
unlikely(current->ptrace & PT_SUSPEND_SECCOMP))
return SECCOMP_PHASE1_OK;
switch (mode) {
case SECCOMP_MODE_STRICT:
__secure_computing_strict(this_syscall); /* may call do_exit */
return SECCOMP_PHASE1_OK;
#ifdef CONFIG_SECCOMP_FILTER
case SECCOMP_MODE_FILTER:
return __seccomp_phase1_filter(this_syscall, sd);
#endif
default:
BUG();
}
}
/**
* seccomp_phase2() - finish slow path seccomp work for the current syscall
* @phase1_result: The return value from seccomp_phase1()
*
* This must be called from a context in which ptrace hooks can be used.
*
* Returns 0 if the syscall should be processed or -1 to skip the syscall.
*/
int seccomp_phase2(u32 phase1_result)
{
struct pt_regs *regs = task_pt_regs(current);
u32 action = phase1_result & SECCOMP_RET_ACTION;
int data = phase1_result & SECCOMP_RET_DATA;
BUG_ON(action != SECCOMP_RET_TRACE);
audit_seccomp(syscall_get_nr(current, regs), 0, action);
/* Skip these calls if there is no tracer. */
if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) {
syscall_set_return_value(current, regs,
-ENOSYS, 0);
return -1;
}
/* 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.
* Terminating the task now avoids executing a system
* call that may not be intended.
*/
if (fatal_signal_pending(current))
do_exit(SIGSYS);
if (syscall_get_nr(current, regs) < 0)
return -1; /* Explicit request to skip. */
return 0;
}
#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);
ret = 0;
out:
spin_unlock_irq(&current->sighand->siglock);
return ret;
}
#ifdef CONFIG_SECCOMP_FILTER
/**
* 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;
/* Validate flags. */
if (flags & ~SECCOMP_FILTER_FLAG_MASK)
return -EINVAL;
/* Prepare the new filter before holding any locks. */
prepared = seccomp_prepare_user_filter(filter);
if (IS_ERR(prepared))
return PTR_ERR(prepared);
/*
* 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_free;
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);
out:
spin_unlock_irq(&current->sighand->siglock);
if (flags & SECCOMP_FILTER_FLAG_TSYNC)
mutex_unlock(&current->signal->cred_guard_mutex);
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
/* Common entry point for both prctl and syscall. */
static long do_seccomp(unsigned int op, unsigned int flags,
const char __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);
default:
return -EINVAL;
}
}
SYSCALL_DEFINE3(seccomp, unsigned int, op, unsigned int, flags,
const char __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, char __user *filter)
{
unsigned int op;
char __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)
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;
unsigned long count = 0;
if (!capable(CAP_SYS_ADMIN) ||
current->seccomp.mode != SECCOMP_MODE_DISABLED) {
return -EACCES;
}
spin_lock_irq(&task->sighand->siglock);
if (task->seccomp.mode != SECCOMP_MODE_FILTER) {
ret = -EINVAL;
goto out;
}
filter = task->seccomp.filter;
while (filter) {
filter = filter->prev;
count++;
}
if (filter_off >= count) {
ret = -ENOENT;
goto out;
}
count -= filter_off;
filter = task->seccomp.filter;
while (filter && count > 1) {
filter = filter->prev;
count--;
}
if (WARN_ON(count != 1 || !filter)) {
/* The filter tree shouldn't shrink while we're using it. */
ret = -ENOENT;
goto out;
}
fprog = filter->prog->orig_prog;
if (!fprog) {
/* This must be a new non-cBPF filter, since we save every
* every cBPF filter's orig_prog above when
* CONFIG_CHECKPOINT_RESTORE is enabled.
*/
ret = -EMEDIUMTYPE;
goto out;
}
ret = fprog->len;
if (!data)
goto out;
get_seccomp_filter(task);
spin_unlock_irq(&task->sighand->siglock);
if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog)))
ret = -EFAULT;
put_seccomp_filter(task);
return ret;
out:
spin_unlock_irq(&task->sighand->siglock);
return ret;
}
#endif