On Tue, Sep 08, 2020 at 12:35:18PM -0700, Kees Cook wrote:
> While we testing for the behavior of unknown seccomp filter return
s/we/we're/
> values, there was no test for how it acted in a thread group. Add
> a test in the thread group tests for this.
>
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> ---
> (This is going via the seccomp tree.)
> ---
Thanks!
Acked-by: Christian Brauner <christian.brauner@xxxxxxxxxx>
> tools/testing/selftests/seccomp/seccomp_bpf.c | 43 ++++++++++++++++---
> 1 file changed, 37 insertions(+), 6 deletions(-)
>
> diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
> index 7a6d40286a42..bfb382580493 100644
> --- a/tools/testing/selftests/seccomp/seccomp_bpf.c
> +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
> @@ -774,8 +774,15 @@ void *kill_thread(void *data)
> return (void *)SIBLING_EXIT_UNKILLED;
> }
>
> +enum kill_t {
> + KILL_THREAD,
> + KILL_PROCESS,
> + RET_UNKNOWN
> +};
> +
> /* Prepare a thread that will kill itself or both of us. */
> -void kill_thread_or_group(struct __test_metadata *_metadata, bool kill_process)
> +void kill_thread_or_group(struct __test_metadata *_metadata,
> + enum kill_t kill_how)
> {
> pthread_t thread;
> void *status;
> @@ -791,11 +798,12 @@ void kill_thread_or_group(struct __test_metadata *_metadata, bool kill_process)
> .len = (unsigned short)ARRAY_SIZE(filter_thread),
> .filter = filter_thread,
> };
> + int kill = kill_how == KILL_PROCESS ? SECCOMP_RET_KILL_PROCESS : 0xAAAAAAAAA;
> struct sock_filter filter_process[] = {
> 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),
> + BPF_STMT(BPF_RET|BPF_K, kill),
> BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW),
> };
> struct sock_fprog prog_process = {
> @@ -808,13 +816,15 @@ void kill_thread_or_group(struct __test_metadata *_metadata, bool kill_process)
> }
>
> ASSERT_EQ(0, seccomp(SECCOMP_SET_MODE_FILTER, 0,
> - kill_process ? &prog_process : &prog_thread));
> + kill_how == KILL_THREAD ? &prog_thread
> + : &prog_process));
>
> /*
> * Add the KILL_THREAD rule again to make sure that the KILL_PROCESS
> * flag cannot be downgraded by a new filter.
> */
> - ASSERT_EQ(0, seccomp(SECCOMP_SET_MODE_FILTER, 0, &prog_thread));
> + if (kill_how == KILL_PROCESS)
> + ASSERT_EQ(0, seccomp(SECCOMP_SET_MODE_FILTER, 0, &prog_thread));
(Ok, meaning that you still need to observe that the thread-group gets
taken down not just a single thread.)
>
> /* Start a thread that will exit immediately. */
> ASSERT_EQ(0, pthread_create(&thread, NULL, kill_thread, (void *)false));
> @@ -842,7 +852,7 @@ TEST(KILL_thread)
> child_pid = fork();
> ASSERT_LE(0, child_pid);
> if (child_pid == 0) {
> - kill_thread_or_group(_metadata, false);
> + kill_thread_or_group(_metadata, KILL_THREAD);
> _exit(38);
> }
>
> @@ -861,7 +871,7 @@ TEST(KILL_process)
> child_pid = fork();
> ASSERT_LE(0, child_pid);
> if (child_pid == 0) {
> - kill_thread_or_group(_metadata, true);
> + kill_thread_or_group(_metadata, KILL_PROCESS);
> _exit(38);
> }
>
> @@ -872,6 +882,27 @@ TEST(KILL_process)
> ASSERT_EQ(SIGSYS, WTERMSIG(status));
> }
>
> +TEST(KILL_unknown)
> +{
> + int status;
> + pid_t child_pid;
> +
> + child_pid = fork();
> + ASSERT_LE(0, child_pid);
> + if (child_pid == 0) {
> + kill_thread_or_group(_metadata, RET_UNKNOWN);
> + _exit(38);
> + }
> +
> + ASSERT_EQ(child_pid, waitpid(child_pid, &status, 0));
> +
> + /* If the entire process was killed, we'll see SIGSYS. */
> + EXPECT_TRUE(WIFSIGNALED(status)) {
> + TH_LOG("Unknown SECCOMP_RET is only killing the thread?");
> + }
> + ASSERT_EQ(SIGSYS, WTERMSIG(status));
> +}
> +
> /* TODO(wad) add 64-bit versus 32-bit arg tests. */
> TEST(arg_out_of_range)
> {
> --
> 2.25.1
>
>
> --
> Kees Cook
