diff options
Diffstat (limited to 'kernel/seccomp.c')
| -rw-r--r-- | kernel/seccomp.c | 1355 |
1 files changed, 1355 insertions, 0 deletions
diff --git a/kernel/seccomp.c b/kernel/seccomp.c new file mode 100644 index 000000000..69b4e34e1 --- /dev/null +++ b/kernel/seccomp.c @@ -0,0 +1,1355 @@ +// 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> + +/* Not exposed in headers: strictly internal use only. */ +#define SECCOMP_MODE_DEAD (SECCOMP_MODE_FILTER + 1) + +#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/capability.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. + * @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 + * + * seccomp_filter objects are organized in a tree linked via the @prev + * pointer. For any task, it appears to be a singly-linked list starting + * with current->seccomp.filter, the most recently attached or inherited filter. + * However, multiple filters may share a @prev node, by way of fork(), which + * results in a unidirectional tree existing in memory. This is similar to + * how namespaces work. + * + * seccomp_filter objects should never be modified after being attached + * to a task_struct (other than @usage). + */ +struct seccomp_filter { + refcount_t usage; + bool log; + struct seccomp_filter *prev; + struct bpf_prog *prog; +}; + +/* 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 @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) +{ + struct seccomp_data sd_local; + 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 (unlikely(WARN_ON(f == NULL))) + return SECCOMP_RET_KILL_PROCESS; + + 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, 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(¤t->sighand->siglock); + + if (current->seccomp.mode && current->seccomp.mode != seccomp_mode) + return false; + + return true; +} + +void __weak arch_seccomp_spec_mitigate(struct task_struct *task) { } + +static inline void seccomp_assign_mode(struct task_struct *task, + unsigned long seccomp_mode, + unsigned long flags) +{ + assert_spin_locked(&task->sighand->siglock); + + task->seccomp.mode = seccomp_mode; + /* + * Make sure TIF_SECCOMP cannot be set before the mode (and + * filter) is set. + */ + smp_mb__before_atomic(); + /* Assume default seccomp processes want spec flaw mitigation. */ + if ((flags & SECCOMP_FILTER_FLAG_SPEC_ALLOW) == 0) + arch_seccomp_spec_mitigate(task); + set_tsk_thread_flag(task, TIF_SECCOMP); +} + +#ifdef CONFIG_SECCOMP_FILTER +/* Returns 1 if the parent is an ancestor of the child. */ +static int is_ancestor(struct seccomp_filter *parent, + struct seccomp_filter *child) +{ + /* NULL is the root ancestor. */ + if (parent == NULL) + return 1; + for (; child; child = child->prev) + if (child == parent) + return 1; + return 0; +} + +/** + * seccomp_can_sync_threads: checks if all threads can be synchronized + * + * Expects sighand and cred_guard_mutex locks to be held. + * + * Returns 0 on success, -ve on error, or the pid of a thread which was + * either not in the correct seccomp mode or it did not have an ancestral + * seccomp filter. + */ +static inline pid_t seccomp_can_sync_threads(void) +{ + struct task_struct *thread, *caller; + + BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex)); + assert_spin_locked(¤t->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(unsigned long flags) +{ + struct task_struct *thread, *caller; + + BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex)); + assert_spin_locked(¤t->sighand->siglock); + + /* Synchronize all threads. */ + caller = current; + for_each_thread(caller, thread) { + /* Skip current, since it needs no changes. */ + if (thread == caller) + continue; + + /* Get a task reference for the new leaf node. */ + get_seccomp_filter(caller); + /* + * Drop the task reference to the shared ancestor since + * current's path will hold a reference. (This also + * allows a put before the assignment.) + */ + put_seccomp_filter(thread); + smp_store_release(&thread->seccomp.filter, + caller->seccomp.filter); + + /* + * Don't let an unprivileged task work around + * the no_new_privs restriction by creating + * a thread that sets it up, enters seccomp, + * then dies. + */ + if (task_no_new_privs(caller)) + task_set_no_new_privs(thread); + + /* + * Opt the other thread into seccomp if needed. + * As threads are considered to be trust-realm + * equivalent (see ptrace_may_access), it is safe to + * allow one thread to transition the other. + */ + if (thread->seccomp.mode == SECCOMP_MODE_DISABLED) + seccomp_assign_mode(thread, SECCOMP_MODE_FILTER, + flags); + } +} + +/** + * seccomp_prepare_filter: Prepares a seccomp filter for use. + * @fprog: BPF program to install + * + * Returns filter on success or an ERR_PTR on failure. + */ +static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog) +{ + struct seccomp_filter *sfilter; + int ret; + const bool save_orig = IS_ENABLED(CONFIG_CHECKPOINT_RESTORE); + + if (fprog->len == 0 || fprog->len > BPF_MAXINSNS) + return ERR_PTR(-EINVAL); + + BUG_ON(INT_MAX / fprog->len < sizeof(struct sock_filter)); + + /* + * Installing a seccomp filter requires that the task has + * CAP_SYS_ADMIN in its namespace or be running with no_new_privs. + * This avoids scenarios where unprivileged tasks can affect the + * behavior of privileged children. + */ + if (!task_no_new_privs(current) && + !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); + + ret = bpf_prog_create_from_user(&sfilter->prog, fprog, + seccomp_check_filter, save_orig); + if (ret < 0) { + kfree(sfilter); + return ERR_PTR(ret); + } + + refcount_set(&sfilter->usage, 1); + + return sfilter; +} + +/** + * seccomp_prepare_user_filter - prepares a user-supplied sock_fprog + * @user_filter: pointer to the user data containing a sock_fprog. + * + * Returns 0 on success and non-zero otherwise. + */ +static struct seccomp_filter * +seccomp_prepare_user_filter(const char __user *user_filter) +{ + struct sock_fprog fprog; + struct seccomp_filter *filter = ERR_PTR(-EFAULT); + +#ifdef CONFIG_COMPAT + if (in_compat_syscall()) { + struct compat_sock_fprog fprog32; + if (copy_from_user(&fprog32, user_filter, sizeof(fprog32))) + goto out; + fprog.len = fprog32.len; + fprog.filter = compat_ptr(fprog32.filter); + } else /* falls through to the if below. */ +#endif + if (copy_from_user(&fprog, user_filter, sizeof(fprog))) + goto out; + filter = seccomp_prepare_filter(&fprog); +out: + return filter; +} + +/** + * seccomp_attach_filter: validate and attach filter + * @flags: flags to change filter behavior + * @filter: seccomp filter to add to the current process + * + * Caller must be holding current->sighand->siglock lock. + * + * Returns 0 on success, -ve on error. + */ +static long seccomp_attach_filter(unsigned int flags, + struct seccomp_filter *filter) +{ + unsigned long total_insns; + struct seccomp_filter *walker; + + assert_spin_locked(¤t->sighand->siglock); + + /* Validate resulting filter length. */ + total_insns = filter->prog->len; + for (walker = current->seccomp.filter; walker; walker = walker->prev) + total_insns += walker->prog->len + 4; /* 4 instr penalty */ + if (total_insns > MAX_INSNS_PER_PATH) + return -ENOMEM; + + /* If thread sync has been requested, check that it is possible. */ + if (flags & SECCOMP_FILTER_FLAG_TSYNC) { + int ret; + + ret = seccomp_can_sync_threads(); + if (ret) + return ret; + } + + /* Set log flag, if present. */ + if (flags & SECCOMP_FILTER_FLAG_LOG) + filter->log = true; + + /* + * If there is an existing filter, make it the prev and don't drop its + * task reference. + */ + filter->prev = current->seccomp.filter; + current->seccomp.filter = filter; + + /* Now that the new filter is in place, synchronize to all threads. */ + if (flags & SECCOMP_FILTER_FLAG_TSYNC) + seccomp_sync_threads(flags); + + return 0; +} + +static void __get_seccomp_filter(struct seccomp_filter *filter) +{ + /* Reference count is bounded by the number of total processes. */ + refcount_inc(&filter->usage); +} + +/* get_seccomp_filter - increments the reference count of the filter on @tsk */ +void get_seccomp_filter(struct task_struct *tsk) +{ + struct seccomp_filter *orig = tsk->seccomp.filter; + if (!orig) + return; + __get_seccomp_filter(orig); +} + +static inline void seccomp_filter_free(struct seccomp_filter *filter) +{ + if (filter) { + bpf_prog_destroy(filter->prog); + kfree(filter); + } +} + +static void __put_seccomp_filter(struct seccomp_filter *orig) +{ + /* Clean up single-reference branches iteratively. */ + while (orig && refcount_dec_and_test(&orig->usage)) { + struct seccomp_filter *freeme = orig; + orig = orig->prev; + seccomp_filter_free(freeme); + } +} + +/* put_seccomp_filter - decrements the ref count of tsk->seccomp.filter */ +void put_seccomp_filter(struct task_struct *tsk) +{ + __put_seccomp_filter(tsk->seccomp.filter); +} + +static void seccomp_init_siginfo(siginfo_t *info, int syscall, int reason) +{ + clear_siginfo(info); + info->si_signo = SIGSYS; + info->si_code = SYS_SECCOMP; + info->si_call_addr = (void __user *)KSTK_EIP(current); + info->si_errno = reason; + info->si_arch = syscall_get_arch(); + info->si_syscall = syscall; +} + +/** + * seccomp_send_sigsys - signals the task to allow in-process syscall emulation + * @syscall: syscall number to send to userland + * @reason: filter-supplied reason code to send to userland (via si_errno) + * + * Forces a SIGSYS with a code of SYS_SECCOMP and related sigsys info. + */ +static void seccomp_send_sigsys(int syscall, int reason) +{ + struct siginfo info; + seccomp_init_siginfo(&info, syscall, reason); + force_sig_info(SIGSYS, &info, current); +} +#endif /* CONFIG_SECCOMP_FILTER */ + +/* For use with seccomp_actions_logged */ +#define SECCOMP_LOG_KILL_PROCESS (1 << 0) +#define SECCOMP_LOG_KILL_THREAD (1 << 1) +#define SECCOMP_LOG_TRAP (1 << 2) +#define SECCOMP_LOG_ERRNO (1 << 3) +#define SECCOMP_LOG_TRACE (1 << 4) +#define SECCOMP_LOG_LOG (1 << 5) +#define SECCOMP_LOG_ALLOW (1 << 6) + +static u32 seccomp_actions_logged = SECCOMP_LOG_KILL_PROCESS | + SECCOMP_LOG_KILL_THREAD | + SECCOMP_LOG_TRAP | + SECCOMP_LOG_ERRNO | + 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_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 + current->seccomp.mode = SECCOMP_MODE_DEAD; + 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 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; + + /* + * 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, &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_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: + current->seccomp.mode = SECCOMP_MODE_DEAD; + 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) { + 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(); + + 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, 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); + /* Surviving SECCOMP_RET_KILL_* must be proactively impossible. */ + case SECCOMP_MODE_DEAD: + WARN_ON_ONCE(1); + do_exit(SIGKILL); + return -1; + 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(¤t->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(¤t->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(¤t->signal->cred_guard_mutex)) + goto out_free; + + spin_lock_irq(¤t->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(¤t->sighand->siglock); + if (flags & SECCOMP_FILTER_FLAG_TSYNC) + mutex_unlock(¤t->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 + +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_TRACE: + case SECCOMP_RET_LOG: + case SECCOMP_RET_ALLOW: + break; + default: + return -EOPNOTSUPP; + } + + return 0; +} + +/* 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); + case SECCOMP_GET_ACTION_AVAIL: + if (flags != 0) + return -EINVAL; + + return seccomp_get_action_avail(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) +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_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_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_TRACE, SECCOMP_RET_TRACE_NAME }, + { SECCOMP_LOG_LOG, SECCOMP_RET_LOG_NAME }, + { SECCOMP_LOG_ALLOW, SECCOMP_RET_ALLOW_NAME }, + { } +}; + +static bool seccomp_names_from_actions_logged(char *names, size_t size, + u32 actions_logged, + const char *sep) +{ + const struct seccomp_log_name *cur; + bool append_sep = false; + + for (cur = seccomp_log_names; cur->name && size; cur++) { + ssize_t ret; + + if (!(actions_logged & cur->log)) + continue; + + if (append_sep) { + ret = strscpy(names, sep, size); + if (ret < 0) + return false; + + names += ret; + size -= ret; + } else + append_sep = true; + + ret = strscpy(names, cur->name, size); + if (ret < 0) + return false; + + names += ret; + size -= ret; + } + + return true; +} + +static bool seccomp_action_logged_from_name(u32 *action_logged, + const char *name) +{ + const struct seccomp_log_name *cur; + + for (cur = seccomp_log_names; cur->name; cur++) { + if (!strcmp(cur->name, name)) { + *action_logged = cur->log; + return true; + } + } + + return false; +} + +static bool seccomp_actions_logged_from_names(u32 *actions_logged, char *names) +{ + char *name; + + *actions_logged = 0; + while ((name = strsep(&names, " ")) && *name) { + u32 action_logged = 0; + + if (!seccomp_action_logged_from_name(&action_logged, name)) + return false; + + *actions_logged |= action_logged; + } + + return true; +} + +static int read_actions_logged(struct ctl_table *ro_table, void __user *buffer, + size_t *lenp, loff_t *ppos) +{ + char names[sizeof(seccomp_actions_avail)]; + struct ctl_table table; + + memset(names, 0, sizeof(names)); + + if (!seccomp_names_from_actions_logged(names, sizeof(names), + seccomp_actions_logged, " ")) + return -EINVAL; + + table = *ro_table; + table.data = names; + table.maxlen = sizeof(names); + return proc_dostring(&table, 0, buffer, lenp, ppos); +} + +static int write_actions_logged(struct ctl_table *ro_table, void __user *buffer, + size_t *lenp, loff_t *ppos, u32 *actions_logged) +{ + char names[sizeof(seccomp_actions_avail)]; + struct ctl_table table; + int ret; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + memset(names, 0, sizeof(names)); + + table = *ro_table; + table.data = names; + table.maxlen = sizeof(names); + ret = proc_dostring(&table, 1, buffer, lenp, ppos); + if (ret) + return ret; + + if (!seccomp_actions_logged_from_names(actions_logged, table.data)) + return -EINVAL; + + if (*actions_logged & SECCOMP_LOG_ALLOW) + return -EINVAL; + + seccomp_actions_logged = *actions_logged; + return 0; +} + +static void audit_actions_logged(u32 actions_logged, u32 old_actions_logged, + int ret) +{ + char names[sizeof(seccomp_actions_avail)]; + char old_names[sizeof(seccomp_actions_avail)]; + const char *new = names; + const char *old = old_names; + + if (!audit_enabled) + return; + + memset(names, 0, sizeof(names)); + memset(old_names, 0, sizeof(old_names)); + + if (ret) + new = "?"; + else if (!actions_logged) + new = "(none)"; + else if (!seccomp_names_from_actions_logged(names, sizeof(names), + actions_logged, ",")) + new = "?"; + + if (!old_actions_logged) + old = "(none)"; + else if (!seccomp_names_from_actions_logged(old_names, + sizeof(old_names), + old_actions_logged, ",")) + old = "?"; + + return audit_seccomp_actions_logged(new, old, !ret); +} + +static int seccomp_actions_logged_handler(struct ctl_table *ro_table, int write, + void __user *buffer, size_t *lenp, + loff_t *ppos) +{ + int ret; + + if (write) { + u32 actions_logged = 0; + u32 old_actions_logged = seccomp_actions_logged; + + ret = write_actions_logged(ro_table, buffer, lenp, ppos, + &actions_logged); + audit_actions_logged(actions_logged, old_actions_logged, ret); + } else + ret = read_actions_logged(ro_table, buffer, lenp, ppos); + + return ret; +} + +static struct ctl_path seccomp_sysctl_path[] = { + { .procname = "kernel", }, + { .procname = "seccomp", }, + { } +}; + +static struct ctl_table seccomp_sysctl_table[] = { + { + .procname = "actions_avail", + .data = (void *) &seccomp_actions_avail, + .maxlen = sizeof(seccomp_actions_avail), + .mode = 0444, + .proc_handler = proc_dostring, + }, + { + .procname = "actions_logged", + .mode = 0644, + .proc_handler = seccomp_actions_logged_handler, + }, + { } +}; + +static int __init seccomp_sysctl_init(void) +{ + struct ctl_table_header *hdr; + + hdr = register_sysctl_paths(seccomp_sysctl_path, seccomp_sysctl_table); + if (!hdr) + pr_warn("seccomp: sysctl registration failed\n"); + else + kmemleak_not_leak(hdr); + + return 0; +} + +device_initcall(seccomp_sysctl_init) + +#endif /* CONFIG_SYSCTL */ |