diff options
Diffstat (limited to 'kernel/seccomp.c')
| -rw-r--r-- | kernel/seccomp.c | 904 |
1 files changed, 904 insertions, 0 deletions
diff --git a/kernel/seccomp.c b/kernel/seccomp.c new file mode 100644 index 000000000..4f4402894 --- /dev/null +++ b/kernel/seccomp.c @@ -0,0 +1,904 @@ +/* + * 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_filter *f = ACCESS_ONCE(current->seccomp.filter); + struct seccomp_data sd_local; + u32 ret = SECCOMP_RET_ALLOW; + + /* Ensure unexpected behavior doesn't result in failing open. */ + if (unlikely(WARN_ON(f == NULL))) + return SECCOMP_RET_KILL; + + /* Make sure cross-thread synced filter points somewhere sane. */ + smp_read_barrier_depends(); + + 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(¤t->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(¤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(void) +{ + 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); + /* + * 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 *filter; + unsigned long fp_size; + struct sock_filter *fp; + int new_len; + long ret; + + if (fprog->len == 0 || fprog->len > BPF_MAXINSNS) + return ERR_PTR(-EINVAL); + BUG_ON(INT_MAX / fprog->len < sizeof(struct sock_filter)); + fp_size = 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); + + fp = kzalloc(fp_size, GFP_KERNEL|__GFP_NOWARN); + if (!fp) + return ERR_PTR(-ENOMEM); + + /* Copy the instructions from fprog. */ + ret = -EFAULT; + if (copy_from_user(fp, fprog->filter, fp_size)) + goto free_prog; + + /* Check and rewrite the fprog via the skb checker */ + ret = bpf_check_classic(fp, fprog->len); + if (ret) + goto free_prog; + + /* Check and rewrite the fprog for seccomp use */ + ret = seccomp_check_filter(fp, fprog->len); + if (ret) + goto free_prog; + + /* Convert 'sock_filter' insns to 'bpf_insn' insns */ + ret = bpf_convert_filter(fp, fprog->len, NULL, &new_len); + if (ret) + goto free_prog; + + /* Allocate a new seccomp_filter */ + ret = -ENOMEM; + filter = kzalloc(sizeof(struct seccomp_filter), + GFP_KERNEL|__GFP_NOWARN); + if (!filter) + goto free_prog; + + filter->prog = bpf_prog_alloc(bpf_prog_size(new_len), __GFP_NOWARN); + if (!filter->prog) + goto free_filter; + + ret = bpf_convert_filter(fp, fprog->len, filter->prog->insnsi, &new_len); + if (ret) + goto free_filter_prog; + + kfree(fp); + atomic_set(&filter->usage, 1); + filter->prog->len = new_len; + + bpf_prog_select_runtime(filter->prog); + + return filter; + +free_filter_prog: + __bpf_prog_free(filter->prog); +free_filter: + kfree(filter); +free_prog: + kfree(fp); + return ERR_PTR(ret); +} + +/** + * 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(¤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; + } + + /* + * 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_free(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 (mode == 0) + 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)); + + 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(¤t->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(¤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); +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 + +/* 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); +} |