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5c38065e02
Seccomp wants to know the syscall bitness, not the caller task bitness, when it selects the syscall whitelist. As far as I know, this makes no difference on any architecture, so it's not a security problem. (It generates identical code everywhere except sparc, and, on sparc, the syscall numbering is the same for both ABIs.) Signed-off-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
944 lines
25 KiB
C
944 lines
25 KiB
C
/*
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* linux/kernel/seccomp.c
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*
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* Copyright 2004-2005 Andrea Arcangeli <andrea@cpushare.com>
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*
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* Copyright (C) 2012 Google, Inc.
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* Will Drewry <wad@chromium.org>
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*
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* This defines a simple but solid secure-computing facility.
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*
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* Mode 1 uses a fixed list of allowed system calls.
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* Mode 2 allows user-defined system call filters in the form
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* of Berkeley Packet Filters/Linux Socket Filters.
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*/
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#include <linux/atomic.h>
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#include <linux/audit.h>
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#include <linux/compat.h>
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#include <linux/sched.h>
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#include <linux/seccomp.h>
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#include <linux/slab.h>
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#include <linux/syscalls.h>
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#ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
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#include <asm/syscall.h>
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#endif
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#ifdef CONFIG_SECCOMP_FILTER
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#include <linux/filter.h>
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#include <linux/pid.h>
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#include <linux/ptrace.h>
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#include <linux/security.h>
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#include <linux/tracehook.h>
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#include <linux/uaccess.h>
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/**
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* struct seccomp_filter - container for seccomp BPF programs
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*
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* @usage: reference count to manage the object lifetime.
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* get/put helpers should be used when accessing an instance
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* outside of a lifetime-guarded section. In general, this
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* is only needed for handling filters shared across tasks.
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* @prev: points to a previously installed, or inherited, filter
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* @len: the number of instructions in the program
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* @insnsi: the BPF program instructions to evaluate
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*
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* seccomp_filter objects are organized in a tree linked via the @prev
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* pointer. For any task, it appears to be a singly-linked list starting
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* with current->seccomp.filter, the most recently attached or inherited filter.
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* However, multiple filters may share a @prev node, by way of fork(), which
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* results in a unidirectional tree existing in memory. This is similar to
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* how namespaces work.
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*
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* seccomp_filter objects should never be modified after being attached
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* to a task_struct (other than @usage).
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*/
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struct seccomp_filter {
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atomic_t usage;
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struct seccomp_filter *prev;
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struct bpf_prog *prog;
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};
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/* Limit any path through the tree to 256KB worth of instructions. */
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#define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter))
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/*
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* Endianness is explicitly ignored and left for BPF program authors to manage
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* as per the specific architecture.
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*/
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static void populate_seccomp_data(struct seccomp_data *sd)
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{
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struct task_struct *task = current;
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struct pt_regs *regs = task_pt_regs(task);
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unsigned long args[6];
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sd->nr = syscall_get_nr(task, regs);
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sd->arch = syscall_get_arch();
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syscall_get_arguments(task, regs, 0, 6, args);
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sd->args[0] = args[0];
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sd->args[1] = args[1];
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sd->args[2] = args[2];
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sd->args[3] = args[3];
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sd->args[4] = args[4];
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sd->args[5] = args[5];
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sd->instruction_pointer = KSTK_EIP(task);
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}
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/**
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* seccomp_check_filter - verify seccomp filter code
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* @filter: filter to verify
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* @flen: length of filter
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*
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* Takes a previously checked filter (by bpf_check_classic) and
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* redirects all filter code that loads struct sk_buff data
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* and related data through seccomp_bpf_load. It also
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* enforces length and alignment checking of those loads.
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*
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* Returns 0 if the rule set is legal or -EINVAL if not.
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*/
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static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen)
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{
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int pc;
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for (pc = 0; pc < flen; pc++) {
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struct sock_filter *ftest = &filter[pc];
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u16 code = ftest->code;
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u32 k = ftest->k;
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switch (code) {
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case BPF_LD | BPF_W | BPF_ABS:
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ftest->code = BPF_LDX | BPF_W | BPF_ABS;
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/* 32-bit aligned and not out of bounds. */
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if (k >= sizeof(struct seccomp_data) || k & 3)
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return -EINVAL;
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continue;
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case BPF_LD | BPF_W | BPF_LEN:
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ftest->code = BPF_LD | BPF_IMM;
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ftest->k = sizeof(struct seccomp_data);
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continue;
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case BPF_LDX | BPF_W | BPF_LEN:
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ftest->code = BPF_LDX | BPF_IMM;
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ftest->k = sizeof(struct seccomp_data);
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continue;
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/* Explicitly include allowed calls. */
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case BPF_RET | BPF_K:
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case BPF_RET | BPF_A:
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case BPF_ALU | BPF_ADD | BPF_K:
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case BPF_ALU | BPF_ADD | BPF_X:
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case BPF_ALU | BPF_SUB | BPF_K:
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case BPF_ALU | BPF_SUB | BPF_X:
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case BPF_ALU | BPF_MUL | BPF_K:
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case BPF_ALU | BPF_MUL | BPF_X:
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case BPF_ALU | BPF_DIV | BPF_K:
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case BPF_ALU | BPF_DIV | BPF_X:
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case BPF_ALU | BPF_AND | BPF_K:
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case BPF_ALU | BPF_AND | BPF_X:
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case BPF_ALU | BPF_OR | BPF_K:
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case BPF_ALU | BPF_OR | BPF_X:
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case BPF_ALU | BPF_XOR | BPF_K:
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case BPF_ALU | BPF_XOR | BPF_X:
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case BPF_ALU | BPF_LSH | BPF_K:
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case BPF_ALU | BPF_LSH | BPF_X:
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case BPF_ALU | BPF_RSH | BPF_K:
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case BPF_ALU | BPF_RSH | BPF_X:
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case BPF_ALU | BPF_NEG:
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case BPF_LD | BPF_IMM:
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case BPF_LDX | BPF_IMM:
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case BPF_MISC | BPF_TAX:
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case BPF_MISC | BPF_TXA:
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case BPF_LD | BPF_MEM:
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case BPF_LDX | BPF_MEM:
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case BPF_ST:
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case BPF_STX:
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case BPF_JMP | BPF_JA:
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case BPF_JMP | BPF_JEQ | BPF_K:
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case BPF_JMP | BPF_JEQ | BPF_X:
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case BPF_JMP | BPF_JGE | BPF_K:
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case BPF_JMP | BPF_JGE | BPF_X:
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case BPF_JMP | BPF_JGT | BPF_K:
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case BPF_JMP | BPF_JGT | BPF_X:
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case BPF_JMP | BPF_JSET | BPF_K:
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case BPF_JMP | BPF_JSET | BPF_X:
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continue;
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default:
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return -EINVAL;
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}
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}
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return 0;
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}
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/**
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* seccomp_run_filters - evaluates all seccomp filters against @syscall
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* @syscall: number of the current system call
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*
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* Returns valid seccomp BPF response codes.
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*/
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static u32 seccomp_run_filters(struct seccomp_data *sd)
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{
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struct seccomp_data sd_local;
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u32 ret = SECCOMP_RET_ALLOW;
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/* Make sure cross-thread synced filter points somewhere sane. */
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struct seccomp_filter *f =
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lockless_dereference(current->seccomp.filter);
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/* Ensure unexpected behavior doesn't result in failing open. */
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if (unlikely(WARN_ON(f == NULL)))
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return SECCOMP_RET_KILL;
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if (!sd) {
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populate_seccomp_data(&sd_local);
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sd = &sd_local;
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}
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/*
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* All filters in the list are evaluated and the lowest BPF return
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* value always takes priority (ignoring the DATA).
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*/
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for (; f; f = f->prev) {
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u32 cur_ret = BPF_PROG_RUN(f->prog, (void *)sd);
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if ((cur_ret & SECCOMP_RET_ACTION) < (ret & SECCOMP_RET_ACTION))
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ret = cur_ret;
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}
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return ret;
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}
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#endif /* CONFIG_SECCOMP_FILTER */
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static inline bool seccomp_may_assign_mode(unsigned long seccomp_mode)
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{
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assert_spin_locked(¤t->sighand->siglock);
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if (current->seccomp.mode && current->seccomp.mode != seccomp_mode)
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return false;
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return true;
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}
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static inline void seccomp_assign_mode(struct task_struct *task,
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unsigned long seccomp_mode)
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{
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assert_spin_locked(&task->sighand->siglock);
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task->seccomp.mode = seccomp_mode;
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/*
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* Make sure TIF_SECCOMP cannot be set before the mode (and
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* filter) is set.
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*/
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smp_mb__before_atomic();
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set_tsk_thread_flag(task, TIF_SECCOMP);
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}
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#ifdef CONFIG_SECCOMP_FILTER
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/* Returns 1 if the parent is an ancestor of the child. */
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static int is_ancestor(struct seccomp_filter *parent,
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struct seccomp_filter *child)
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{
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/* NULL is the root ancestor. */
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if (parent == NULL)
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return 1;
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for (; child; child = child->prev)
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if (child == parent)
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return 1;
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return 0;
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}
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/**
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* seccomp_can_sync_threads: checks if all threads can be synchronized
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*
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* Expects sighand and cred_guard_mutex locks to be held.
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*
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* Returns 0 on success, -ve on error, or the pid of a thread which was
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* either not in the correct seccomp mode or it did not have an ancestral
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* seccomp filter.
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*/
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static inline pid_t seccomp_can_sync_threads(void)
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{
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struct task_struct *thread, *caller;
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BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex));
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assert_spin_locked(¤t->sighand->siglock);
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/* Validate all threads being eligible for synchronization. */
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caller = current;
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for_each_thread(caller, thread) {
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pid_t failed;
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/* Skip current, since it is initiating the sync. */
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if (thread == caller)
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continue;
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if (thread->seccomp.mode == SECCOMP_MODE_DISABLED ||
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(thread->seccomp.mode == SECCOMP_MODE_FILTER &&
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is_ancestor(thread->seccomp.filter,
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caller->seccomp.filter)))
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continue;
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/* Return the first thread that cannot be synchronized. */
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failed = task_pid_vnr(thread);
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/* If the pid cannot be resolved, then return -ESRCH */
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if (unlikely(WARN_ON(failed == 0)))
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failed = -ESRCH;
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return failed;
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}
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return 0;
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}
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/**
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* seccomp_sync_threads: sets all threads to use current's filter
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*
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* Expects sighand and cred_guard_mutex locks to be held, and for
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* seccomp_can_sync_threads() to have returned success already
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* without dropping the locks.
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*
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*/
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static inline void seccomp_sync_threads(void)
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{
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struct task_struct *thread, *caller;
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BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex));
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assert_spin_locked(¤t->sighand->siglock);
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/* Synchronize all threads. */
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caller = current;
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for_each_thread(caller, thread) {
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/* Skip current, since it needs no changes. */
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if (thread == caller)
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continue;
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/* Get a task reference for the new leaf node. */
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get_seccomp_filter(caller);
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/*
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* Drop the task reference to the shared ancestor since
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* current's path will hold a reference. (This also
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* allows a put before the assignment.)
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*/
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put_seccomp_filter(thread);
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smp_store_release(&thread->seccomp.filter,
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caller->seccomp.filter);
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/*
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* Don't let an unprivileged task work around
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* the no_new_privs restriction by creating
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* a thread that sets it up, enters seccomp,
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* then dies.
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*/
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if (task_no_new_privs(caller))
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task_set_no_new_privs(thread);
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/*
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* Opt the other thread into seccomp if needed.
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* As threads are considered to be trust-realm
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* equivalent (see ptrace_may_access), it is safe to
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* allow one thread to transition the other.
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*/
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if (thread->seccomp.mode == SECCOMP_MODE_DISABLED)
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seccomp_assign_mode(thread, SECCOMP_MODE_FILTER);
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}
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}
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/**
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* seccomp_prepare_filter: Prepares a seccomp filter for use.
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* @fprog: BPF program to install
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*
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* Returns filter on success or an ERR_PTR on failure.
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*/
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static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog)
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{
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struct seccomp_filter *sfilter;
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int ret;
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const bool save_orig = config_enabled(CONFIG_CHECKPOINT_RESTORE);
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if (fprog->len == 0 || fprog->len > BPF_MAXINSNS)
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return ERR_PTR(-EINVAL);
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BUG_ON(INT_MAX / fprog->len < sizeof(struct sock_filter));
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/*
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* Installing a seccomp filter requires that the task has
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* CAP_SYS_ADMIN in its namespace or be running with no_new_privs.
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* This avoids scenarios where unprivileged tasks can affect the
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* behavior of privileged children.
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*/
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if (!task_no_new_privs(current) &&
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security_capable_noaudit(current_cred(), current_user_ns(),
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CAP_SYS_ADMIN) != 0)
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return ERR_PTR(-EACCES);
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/* Allocate a new seccomp_filter */
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sfilter = kzalloc(sizeof(*sfilter), GFP_KERNEL | __GFP_NOWARN);
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if (!sfilter)
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return ERR_PTR(-ENOMEM);
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ret = bpf_prog_create_from_user(&sfilter->prog, fprog,
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seccomp_check_filter, save_orig);
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if (ret < 0) {
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kfree(sfilter);
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return ERR_PTR(ret);
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}
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atomic_set(&sfilter->usage, 1);
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return sfilter;
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}
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/**
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* seccomp_prepare_user_filter - prepares a user-supplied sock_fprog
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* @user_filter: pointer to the user data containing a sock_fprog.
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*
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* Returns 0 on success and non-zero otherwise.
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*/
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static struct seccomp_filter *
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seccomp_prepare_user_filter(const char __user *user_filter)
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{
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struct sock_fprog fprog;
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struct seccomp_filter *filter = ERR_PTR(-EFAULT);
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#ifdef CONFIG_COMPAT
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if (in_compat_syscall()) {
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struct compat_sock_fprog fprog32;
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if (copy_from_user(&fprog32, user_filter, sizeof(fprog32)))
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goto out;
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fprog.len = fprog32.len;
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fprog.filter = compat_ptr(fprog32.filter);
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} else /* falls through to the if below. */
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#endif
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if (copy_from_user(&fprog, user_filter, sizeof(fprog)))
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goto out;
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filter = seccomp_prepare_filter(&fprog);
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out:
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return filter;
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}
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|
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/**
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* seccomp_attach_filter: validate and attach filter
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* @flags: flags to change filter behavior
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* @filter: seccomp filter to add to the current process
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*
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* Caller must be holding current->sighand->siglock lock.
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*
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* Returns 0 on success, -ve on error.
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*/
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static long seccomp_attach_filter(unsigned int flags,
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struct seccomp_filter *filter)
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{
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unsigned long total_insns;
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struct seccomp_filter *walker;
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assert_spin_locked(¤t->sighand->siglock);
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/* Validate resulting filter length. */
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total_insns = filter->prog->len;
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for (walker = current->seccomp.filter; walker; walker = walker->prev)
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total_insns += walker->prog->len + 4; /* 4 instr penalty */
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if (total_insns > MAX_INSNS_PER_PATH)
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return -ENOMEM;
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/* If thread sync has been requested, check that it is possible. */
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if (flags & SECCOMP_FILTER_FLAG_TSYNC) {
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int ret;
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ret = seccomp_can_sync_threads();
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if (ret)
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return ret;
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}
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|
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/*
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* If there is an existing filter, make it the prev and don't drop its
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* task reference.
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*/
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filter->prev = current->seccomp.filter;
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current->seccomp.filter = filter;
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|
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/* Now that the new filter is in place, synchronize to all threads. */
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if (flags & SECCOMP_FILTER_FLAG_TSYNC)
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seccomp_sync_threads();
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return 0;
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}
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|
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/* get_seccomp_filter - increments the reference count of the filter on @tsk */
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void get_seccomp_filter(struct task_struct *tsk)
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{
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struct seccomp_filter *orig = tsk->seccomp.filter;
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if (!orig)
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return;
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/* Reference count is bounded by the number of total processes. */
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atomic_inc(&orig->usage);
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}
|
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|
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static inline void seccomp_filter_free(struct seccomp_filter *filter)
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{
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if (filter) {
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bpf_prog_destroy(filter->prog);
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kfree(filter);
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}
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}
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|
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/* put_seccomp_filter - decrements the ref count of tsk->seccomp.filter */
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void put_seccomp_filter(struct task_struct *tsk)
|
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{
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struct seccomp_filter *orig = tsk->seccomp.filter;
|
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/* 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 (in_compat_syscall())
|
|
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(¤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);
|
|
}
|
|
|
|
#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
|