From: Sargun Dhillon <sargun@sargun.me>
To: Kees Cook <keescook@chromium.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Linux Containers <containers@lists.linux-foundation.org>,
Rodrigo Campos <rodrigo@kinvolk.io>,
Christian Brauner <christian.brauner@ubuntu.com>,
Giuseppe Scrivano <gscrivan@redhat.com>,
Will Drewry <wad@chromium.org>,
Andy Lutomirski <luto@amacapital.net>,
Alban Crequy <alban@kinvolk.io>,
Tycho Andersen <tycho@tycho.pizza>
Subject: Re: [PATCH v3 2/2] selftests/seccomp: Add test for wait killable notifier
Date: Fri, 29 Apr 2022 22:35:57 +0000 [thread overview]
Message-ID: <20220429223557.GB1267404@ircssh-3.c.rugged-nimbus-611.internal> (raw)
In-Reply-To: <202204291053.E04A367@keescook>
On Fri, Apr 29, 2022 at 11:19:33AM -0700, Kees Cook wrote:
> On Thu, Apr 28, 2022 at 07:31:13PM -0700, Sargun Dhillon wrote:
> > +
> > + ASSERT_EQ(socketpair(PF_LOCAL, SOCK_SEQPACKET, 0, sk_pair), 0);
> > +
> > + listener = user_notif_syscall(__NR_getppid,
> > + SECCOMP_FILTER_FLAG_NEW_LISTENER |
> > + SECCOMP_FILTER_FLAG_WAIT_KILLABLE_RECV);
> > + ASSERT_GE(listener, 0);
> > +
> > + pid = fork();
> > + ASSERT_GE(pid, 0);
> > +
> > + if (pid == 0) {
> > + close(sk_pair[0]);
> > + handled = sk_pair[1];
> > +
> > + /* Setup the sigaction without SA_RESTART */
> > + if (sigaction(SIGUSR1, &new_action, NULL)) {
> > + perror("sigaction");
> > + exit(1);
> > + }
> > +
> > + /* Make sure that the syscall is completed (no EINTR) */
> > + ret = syscall(__NR_getppid);
> > + exit(ret != USER_NOTIF_MAGIC);
> > + }
> > +
> > + while (get_proc_syscall(pid) != __NR_getppid &&
> > + get_proc_stat(pid) != 'S')
> > + nanosleep(&delay, NULL);
> > +
> > + EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_RECV, &req), 0);
> > + /* Kill the process to make sure it enters the wait_killable state */
> > + EXPECT_EQ(kill(pid, SIGUSR1), 0);
> > +
> > + /* TASK_KILLABLE is considered D (Disk Sleep) state */
> > + while (get_proc_stat(pid) != 'D')
> > + nanosleep(&delay, NULL);
>
> Should a NOWAIT waitpid() happen in this loop to make sure this doesn't
> spin forever?
>
> i.e. running these tests on a kernel that doesn't have the support
> shouldn't hang -- yes it'll time out eventually but that's annoying. ;)
>
Wouldn't this bail already because user_notif_syscall would assert out
since the kernel would reject the unknown flag?
I might make this a little helper function, something like:
static void wait_for_state(struct __test_metadata *_metadata, pid_t pid, char wait_for) {
/* 100 ms */
struct timespec delay = { .tv_nsec = 100000000 };
int status;
while (get_proc_stat(pid) != wait_for) {
ASSERT_EQ(waitpid(pid, &status, WNOHANG), 0) {
if (WIFEXITED(status))
TH_LOG("Process %d exited with error code %d", pid, WEXITSTATUS(status));
else if (WIFSIGNALED(status))
TH_LOG("Process %d exited due to signal %d", pid, WTERMSIG(status));
else
TH_LOG("Process %d exited due to unknown reason", pid);
}
nanosleep(&delay, NULL);
}
}
}
> > +
> > + resp.id = req.id;
> > + resp.val = USER_NOTIF_MAGIC;
> > + EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_SEND, &resp), 0);
> > +
> > + /*
> > + * Make sure that the signal handler does get called once we're back in
> > + * userspace.
> > + */
> > + EXPECT_EQ(read(sk_pair[0], &c, 1), 1);
> > + EXPECT_EQ(waitpid(pid, &status, 0), pid);
> > + EXPECT_EQ(true, WIFEXITED(status));
> > + EXPECT_EQ(0, WEXITSTATUS(status));
> > +}
> > +
> > +TEST(user_notification_wait_killable_fatal)
> > +{
> > + struct seccomp_notif req = {};
> > + int listener, status;
> > + pid_t pid;
> > + long ret;
> > + /* 100 ms */
> > + struct timespec delay = { .tv_nsec = 100000000 };
> > +
> > + ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
> > + ASSERT_EQ(0, ret) {
> > + TH_LOG("Kernel does not support PR_SET_NO_NEW_PRIVS!");
> > + }
> > +
> > + listener = user_notif_syscall(__NR_getppid,
> > + SECCOMP_FILTER_FLAG_NEW_LISTENER |
> > + SECCOMP_FILTER_FLAG_WAIT_KILLABLE_RECV);
> > + ASSERT_GE(listener, 0);
> > +
> > + pid = fork();
> > + ASSERT_GE(pid, 0);
> > +
> > + if (pid == 0) {
> > + /* This should never complete */
> > + syscall(__NR_getppid);
> > + exit(1);
> > + }
> > +
> > + while (get_proc_stat(pid) != 'S')
> > + nanosleep(&delay, NULL);
> > +
> > + EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_RECV, &req), 0);
> > + /* Kill the process with a fatal signal */
> > + EXPECT_EQ(kill(pid, SIGTERM), 0);
> > +
> > + EXPECT_EQ(waitpid(pid, &status, 0), pid);
> > + EXPECT_EQ(true, WIFSIGNALED(status));
> > + EXPECT_EQ(SIGTERM, WTERMSIG(status));
> > +}
>
> Should there be a test validating the inverse of this, as in _without_
> SECCOMP_FILTER_FLAG_WAIT_KILLABLE_RECV, how should the above tests
> behave?
Don't we roughly get that from the user_notification_kill_in_middle
and user_notification_signal?
Although, I might cleanup the user_notification_signal test to disable
SA_RESTART like these tests.
>
> Otherwise, looks good! Yay tests!
>
> --
> Kees Cook
next prev parent reply other threads:[~2022-04-29 22:36 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-29 2:31 [PATCH v3 0/2] Handle seccomp notification preemption Sargun Dhillon
2022-04-29 2:31 ` [PATCH v3 1/2] seccomp: Add wait_killable semantic to seccomp user notifier Sargun Dhillon
2022-04-29 9:42 ` Rodrigo Campos
2022-04-29 17:14 ` Sargun Dhillon
2022-04-29 18:20 ` Kees Cook
2022-05-02 12:48 ` Rodrigo Campos
2022-04-29 18:22 ` Kees Cook
2022-05-02 14:15 ` Rodrigo Campos
2022-05-02 16:04 ` Sargun Dhillon
2022-05-03 14:27 ` Rodrigo Campos
2022-04-29 2:31 ` [PATCH v3 2/2] selftests/seccomp: Add test for wait killable notifier Sargun Dhillon
2022-04-29 18:19 ` Kees Cook
2022-04-29 22:35 ` Sargun Dhillon [this message]
2022-04-29 22:43 ` Kees Cook
2022-04-29 9:24 ` [PATCH v3 0/2] Handle seccomp notification preemption Rodrigo Campos
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