[PATCH] selftests/seccomp: Handle namespace failures gracefully

[PATCH] selftests/seccomp: Handle namespace failures gracefully

[Kees Cook]

When running without USERNS or PIDNS the seccomp test would hang since
it was waiting forever for the child to trigger the user notification
since it seems the glibc() abort handler makes a call to getpid(),
which would trap again. This changes the getpid filter to getppid, and
makes sure ASSERTs execute to stop from spawning the listener.

Reported-by: Shuah Khan <shuah@kernel.org>
Fixes: 6a21cc50f0c7 ("seccomp: add a return code to trap to userspace")
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 tools/testing/selftests/seccomp/seccomp_bpf.c | 43 ++++++++++---------
 1 file changed, 23 insertions(+), 20 deletions(-)

diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
index f69d2ee29742..3a280b7efc87 100644
--- a/tools/testing/selftests/seccomp/seccomp_bpf.c
+++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
@@ -3079,9 +3079,9 @@ TEST(user_notification_basic)
 
 	/* Check that we get -ENOSYS with no listener attached */
 	if (pid == 0) {
-		if (user_trap_syscall(__NR_getpid, 0) < 0)
+		if (user_trap_syscall(__NR_getppid, 0) < 0)
 			exit(1);
-		ret = syscall(__NR_getpid);
+		ret = syscall(__NR_getppid);
 		exit(ret >= 0 || errno != ENOSYS);
 	}
 
@@ -3096,12 +3096,12 @@ TEST(user_notification_basic)
 	EXPECT_EQ(seccomp(SECCOMP_SET_MODE_FILTER, 0, &prog), 0);
 
 	/* Check that the basic notification machinery works */
-	listener = user_trap_syscall(__NR_getpid,
+	listener = user_trap_syscall(__NR_getppid,
 				     SECCOMP_FILTER_FLAG_NEW_LISTENER);
 	ASSERT_GE(listener, 0);
 
 	/* Installing a second listener in the chain should EBUSY */
-	EXPECT_EQ(user_trap_syscall(__NR_getpid,
+	EXPECT_EQ(user_trap_syscall(__NR_getppid,
 				    SECCOMP_FILTER_FLAG_NEW_LISTENER),
 		  -1);
 	EXPECT_EQ(errno, EBUSY);
@@ -3110,7 +3110,7 @@ TEST(user_notification_basic)
 	ASSERT_GE(pid, 0);
 
 	if (pid == 0) {
-		ret = syscall(__NR_getpid);
+		ret = syscall(__NR_getppid);
 		exit(ret != USER_NOTIF_MAGIC);
 	}
 
@@ -3128,7 +3128,7 @@ TEST(user_notification_basic)
 	EXPECT_GT(poll(&pollfd, 1, -1), 0);
 	EXPECT_EQ(pollfd.revents, POLLOUT);
 
-	EXPECT_EQ(req.data.nr,  __NR_getpid);
+	EXPECT_EQ(req.data.nr,  __NR_getppid);
 
 	resp.id = req.id;
 	resp.error = 0;
@@ -3160,7 +3160,7 @@ TEST(user_notification_kill_in_middle)
 		TH_LOG("Kernel does not support PR_SET_NO_NEW_PRIVS!");
 	}
 
-	listener = user_trap_syscall(__NR_getpid,
+	listener = user_trap_syscall(__NR_getppid,
 				     SECCOMP_FILTER_FLAG_NEW_LISTENER);
 	ASSERT_GE(listener, 0);
 
@@ -3172,7 +3172,7 @@ TEST(user_notification_kill_in_middle)
 	ASSERT_GE(pid, 0);
 
 	if (pid == 0) {
-		ret = syscall(__NR_getpid);
+		ret = syscall(__NR_getppid);
 		exit(ret != USER_NOTIF_MAGIC);
 	}
 
@@ -3282,7 +3282,7 @@ TEST(user_notification_closed_listener)
 		TH_LOG("Kernel does not support PR_SET_NO_NEW_PRIVS!");
 	}
 
-	listener = user_trap_syscall(__NR_getpid,
+	listener = user_trap_syscall(__NR_getppid,
 				     SECCOMP_FILTER_FLAG_NEW_LISTENER);
 	ASSERT_GE(listener, 0);
 
@@ -3293,7 +3293,7 @@ TEST(user_notification_closed_listener)
 	ASSERT_GE(pid, 0);
 	if (pid == 0) {
 		close(listener);
-		ret = syscall(__NR_getpid);
+		ret = syscall(__NR_getppid);
 		exit(ret != -1 && errno != ENOSYS);
 	}
 
@@ -3316,14 +3316,15 @@ TEST(user_notification_child_pid_ns)
 
 	ASSERT_EQ(unshare(CLONE_NEWUSER | CLONE_NEWPID), 0);
 
-	listener = user_trap_syscall(__NR_getpid, SECCOMP_FILTER_FLAG_NEW_LISTENER);
+	listener = user_trap_syscall(__NR_getppid,
+				     SECCOMP_FILTER_FLAG_NEW_LISTENER);
 	ASSERT_GE(listener, 0);
 
 	pid = fork();
 	ASSERT_GE(pid, 0);
 
 	if (pid == 0)
-		exit(syscall(__NR_getpid) != USER_NOTIF_MAGIC);
+		exit(syscall(__NR_getppid) != USER_NOTIF_MAGIC);
 
 	EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_RECV, &req), 0);
 	EXPECT_EQ(req.pid, pid);
@@ -3355,7 +3356,8 @@ TEST(user_notification_sibling_pid_ns)
 		TH_LOG("Kernel does not support PR_SET_NO_NEW_PRIVS!");
 	}
 
-	listener = user_trap_syscall(__NR_getpid, SECCOMP_FILTER_FLAG_NEW_LISTENER);
+	listener = user_trap_syscall(__NR_getppid,
+				     SECCOMP_FILTER_FLAG_NEW_LISTENER);
 	ASSERT_GE(listener, 0);
 
 	pid = fork();
@@ -3368,7 +3370,7 @@ TEST(user_notification_sibling_pid_ns)
 		ASSERT_GE(pid2, 0);
 
 		if (pid2 == 0)
-			exit(syscall(__NR_getpid) != USER_NOTIF_MAGIC);
+			exit(syscall(__NR_getppid) != USER_NOTIF_MAGIC);
 
 		EXPECT_EQ(waitpid(pid2, &status, 0), pid2);
 		EXPECT_EQ(true, WIFEXITED(status));
@@ -3377,11 +3379,11 @@ TEST(user_notification_sibling_pid_ns)
 	}
 
 	/* Create the sibling ns, and sibling in it. */
-	EXPECT_EQ(unshare(CLONE_NEWPID), 0);
-	EXPECT_EQ(errno, 0);
+	ASSERT_EQ(unshare(CLONE_NEWPID), 0);
+	ASSERT_EQ(errno, 0);
 
 	pid2 = fork();
-	EXPECT_GE(pid2, 0);
+	ASSERT_GE(pid2, 0);
 
 	if (pid2 == 0) {
 		ASSERT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_RECV, &req), 0);
@@ -3389,7 +3391,7 @@ TEST(user_notification_sibling_pid_ns)
 		 * The pid should be 0, i.e. the task is in some namespace that
 		 * we can't "see".
 		 */
-		ASSERT_EQ(req.pid, 0);
+		EXPECT_EQ(req.pid, 0);
 
 		resp.id = req.id;
 		resp.error = 0;
@@ -3419,14 +3421,15 @@ TEST(user_notification_fault_recv)
 
 	ASSERT_EQ(unshare(CLONE_NEWUSER), 0);
 
-	listener = user_trap_syscall(__NR_getpid, SECCOMP_FILTER_FLAG_NEW_LISTENER);
+	listener = user_trap_syscall(__NR_getppid,
+				     SECCOMP_FILTER_FLAG_NEW_LISTENER);
 	ASSERT_GE(listener, 0);
 
 	pid = fork();
 	ASSERT_GE(pid, 0);
 
 	if (pid == 0)
-		exit(syscall(__NR_getpid) != USER_NOTIF_MAGIC);
+		exit(syscall(__NR_getppid) != USER_NOTIF_MAGIC);
 
 	/* Do a bad recv() */
 	EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_RECV, NULL), -1);
-- 
2.17.1


-- 
Kees Cook

Re: [PATCH] selftests/seccomp: Handle namespace failures gracefully

[Tycho Andersen]

On Thu, Apr 11, 2019 at 04:56:31PM -0700, Kees Cook wrote:
> When running without USERNS or PIDNS the seccomp test would hang since
> it was waiting forever for the child to trigger the user notification
> since it seems the glibc() abort handler makes a call to getpid(),
> which would trap again. This changes the getpid filter to getppid, and
> makes sure ASSERTs execute to stop from spawning the listener.
> 
> Reported-by: Shuah Khan <shuah@kernel.org>
> Fixes: 6a21cc50f0c7 ("seccomp: add a return code to trap to userspace")
> Signed-off-by: Kees Cook <keescook@chromium.org>

Sorry for the delay, thanks for looking at this!

Reviewed-by: Tycho Andersen <tycho@tycho.ws>

Re: [PATCH] selftests/seccomp: Handle namespace failures gracefully

[shuah]

On 4/12/19 9:25 AM, Tycho Andersen wrote:
> On Thu, Apr 11, 2019 at 04:56:31PM -0700, Kees Cook wrote:
>> When running without USERNS or PIDNS the seccomp test would hang since
>> it was waiting forever for the child to trigger the user notification
>> since it seems the glibc() abort handler makes a call to getpid(),
>> which would trap again. This changes the getpid filter to getppid, and
>> makes sure ASSERTs execute to stop from spawning the listener.
>>
>> Reported-by: Shuah Khan <shuah@kernel.org>
>> Fixes: 6a21cc50f0c7 ("seccomp: add a return code to trap to userspace")
>> Signed-off-by: Kees Cook <keescook@chromium.org>
> 
> Sorry for the delay, thanks for looking at this!
> 
> Reviewed-by: Tycho Andersen <tycho@tycho.ws>
> 

Thanks both. Should it go into stables. I will pull this and
add stable if that is appropriate.

thanks,
-- Shuah

Re: [PATCH] selftests/seccomp: Handle namespace failures gracefully

[Tycho Andersen]

On Fri, Apr 12, 2019 at 11:07:11AM -0600, shuah wrote:
> On 4/12/19 9:25 AM, Tycho Andersen wrote:
> > On Thu, Apr 11, 2019 at 04:56:31PM -0700, Kees Cook wrote:
> > > When running without USERNS or PIDNS the seccomp test would hang since
> > > it was waiting forever for the child to trigger the user notification
> > > since it seems the glibc() abort handler makes a call to getpid(),
> > > which would trap again. This changes the getpid filter to getppid, and
> > > makes sure ASSERTs execute to stop from spawning the listener.
> > > 
> > > Reported-by: Shuah Khan <shuah@kernel.org>
> > > Fixes: 6a21cc50f0c7 ("seccomp: add a return code to trap to userspace")
> > > Signed-off-by: Kees Cook <keescook@chromium.org>
> > 
> > Sorry for the delay, thanks for looking at this!
> > 
> > Reviewed-by: Tycho Andersen <tycho@tycho.ws>
> > 
> 
> Thanks both. Should it go into stables. I will pull this and
> add stable if that is appropriate.

Yes, for 5.0+ that sounds good.

Thanks!

Tycho