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    Subject[PATCH 2/2] selftests/seccomp: Check for waitid() behavior
    Date
    Verify we can fetch child's siginfo_t from waitid() with __WCHILDSIGINFO.
    Skip if it's not available.

    Signed-off-by: Kees Cook <keescook@chromium.org>
    ---
    tools/testing/selftests/seccomp/seccomp_bpf.c | 130 ++++++++++++++++++
    1 file changed, 130 insertions(+)

    diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
    index 9d126d7fabdb..0c803c2b450e 100644
    --- a/tools/testing/selftests/seccomp/seccomp_bpf.c
    +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
    @@ -268,6 +268,14 @@ struct seccomp_notif_addfd_big {
    #define SECCOMP_FILTER_FLAG_TSYNC_ESRCH (1UL << 4)
    #endif

    +#ifndef SYS_SECCOMP
    +#define SYS_SECCOMP 1
    +#endif
    +
    +#ifndef __WCHILDSIGINFO
    +#define __WCHILDSIGINFO 0x10000000
    +#endif
    +
    #ifndef seccomp
    int seccomp(unsigned int op, unsigned int flags, void *args)
    {
    @@ -765,6 +773,128 @@ TEST_SIGNAL(KILL_one_arg_six, SIGSYS)
    close(fd);
    }

    +FIXTURE(SIGINFO) {
    + pid_t child_pid;
    +};
    +
    +FIXTURE_SETUP(SIGINFO)
    +{
    + self->child_pid = 0;
    +}
    +
    +FIXTURE_TEARDOWN(SIGINFO)
    +{
    + if (self->child_pid > 0)
    + waitpid(self->child_pid, NULL, WNOHANG);
    +}
    +
    +TEST_F(SIGINFO, child)
    +{
    + int status;
    + siginfo_t info = { };
    + /* Kill only when calling __NR_prctl. */
    + struct sock_filter filter[] = {
    + BPF_STMT(BPF_LD|BPF_W|BPF_ABS,
    + offsetof(struct seccomp_data, nr)),
    + BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_prctl, 0, 1),
    + BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_KILL_PROCESS | 0xBA),
    + BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
    + };
    + struct sock_fprog prog = {
    + .len = (unsigned short)ARRAY_SIZE(filter),
    + .filter = filter,
    + };
    +
    + self->child_pid = fork();
    + ASSERT_LE(0, self->child_pid);
    + if (self->child_pid == 0) {
    + ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
    + TH_LOG("Kernel does not support PR_SET_NO_NEW_PRIVS!");
    + }
    + ASSERT_EQ(0, seccomp(SECCOMP_SET_MODE_FILTER, 0, &prog));
    + prctl(PR_GET_SECCOMP, 0, 0, 0, 0);
    + /* Should have died now. */
    + _exit(37);
    + }
    +
    + /* Check siginfo_t contents. */
    + EXPECT_EQ(waitid(P_PID, self->child_pid, &info, WEXITED | WNOWAIT), 0);
    +#if 0
    + struct {
    + int si_signo;
    + int si_code;
    + int si_errno;
    + union __sifields _sifields;
    + }
    +
    + /* SIGCHLD */
    + struct {
    + __kernel_pid_t _pid; /* which child */
    + __kernel_uid32_t _uid; /* sender's uid */
    + int _status; /* exit code */
    + __ARCH_SI_CLOCK_T _utime;
    + __ARCH_SI_CLOCK_T _stime;
    + } _sigchld;
    +#endif
    + ASSERT_EQ(info.si_signo, SIGCHLD);
    + EXPECT_TRUE(info.si_code == CLD_KILLED || info.si_code == CLD_DUMPED);
    + EXPECT_TRUE(info.si_errno == 0);
    + EXPECT_EQ(info.si_pid, self->child_pid);
    +
    + ASSERT_TRUE(WIFSIGNALED(info.si_status));
    + /* TODO: why doesn't this WCOREDUMP() agree with below? */
    + /* EXPECT_TRUE(WCOREDUMP(status)); */
    + EXPECT_EQ(WTERMSIG(info.si_status), SIGSYS);
    +
    +
    + memset(&info, 0, sizeof(info));
    + status = waitid(P_PID, self->child_pid, &info,
    + WEXITED | WNOWAIT | __WCHILDSIGINFO);
    + EXPECT_EQ(status, 0) {
    + if (status < 0 && errno == EINVAL)
    + SKIP(goto skip_siginfo, "Kernel does not support waitid() with __WCHILDSIGINFO");
    + }
    +#if 0
    + /* SIGSYS */
    + struct {
    + void __user *_call_addr;/* calling user insn */
    + int _syscall; /* triggering system call number */
    + unsigned int _arch; /* AUDIT_ARCH_* of syscall */
    + } _sigsys;
    +
    + 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(current);
    + info.si_syscall = syscall;
    +
    +#endif
    + ASSERT_EQ(info.si_signo, SIGSYS);
    + EXPECT_EQ(info.si_code, SYS_SECCOMP);
    + /* EXPECT_EQ(info.si_arch, ...native arch...); */
    + EXPECT_EQ(info.si_syscall, __NR_prctl);
    + /*
    + * The syscall will have happened somewhere near the libc
    + * prctl implementation.
    + */
    + EXPECT_TRUE(info.si_call_addr >= (void *)prctl &&
    + info.si_call_addr <= (void *)prctl + PAGE_SIZE) {
    + TH_LOG("info.si_call_addr: %p", info.si_call_addr);
    + TH_LOG("prctl : %p", prctl);
    + }
    + EXPECT_EQ(info.si_errno, 0xBA);
    +
    +skip_siginfo:
    + /* Check status contents. */
    + ASSERT_EQ(waitpid(self->child_pid, &status, 0), self->child_pid);
    + ASSERT_TRUE(WIFSIGNALED(status));
    + /* TODO: why doesn't this WCOREDUMP() agree with above? */
    + /* EXPECT_TRUE(WCOREDUMP(status)); */
    + EXPECT_EQ(WTERMSIG(status), SIGSYS);
    + self->child_pid = 0;
    +}
    +
    /* This is a thread task to die via seccomp filter violation. */
    void *kill_thread(void *data)
    {
    --
    2.30.2
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