--- /dev/null
+/*
+ * 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);
+}
Code Review / kvmfornfv.git / blobdiff