Hi,
As reported by Kernel Test Robot [1], some pidfd tests fail. This is
due to the use of vfork() which introduced some side effects.
Similarly, while making it more generic, a previous commit made some
Landlock file system tests flaky, and subject to the host's file system
mount configuration.
This series fixes all these side effects by replacing vfork() with
clone3() and CLONE_VFORK, which is cleaner (no arbitrary shared memory)
and makes the Kselftest framework more robust.
I tried different approaches and I found this one to be the cleaner and
less invasive for current test cases.
I successfully ran the following tests (using TEST_F and
fork/clone/clone3) with this series:
- landlock:fs_test
- landlock:net_test
- landlock:ptrace_test
- move_mount_set_group:move_mount_set_group_test
- net/af_unix:scm_pidfd
- perf_events:remove_on_exec
- pidfd:pidfd_getfd_test
- pidfd:pidfd_setns_test
- seccomp:seccomp_bpf
- user_events:abi_test
[1] https://lore.kernel.org/oe-lkp/[email protected]
Regards,
Mickaël Salaün (5):
selftests/pidfd: Fix config for pidfd_setns_test
selftests/landlock: Fix FS tests when run on a private mount point
selftests/harness: Fix fixture teardown
selftests/harness: Fix interleaved scheduling leading to race
conditions
selftests/harness: Fix vfork() side effects and uncaught errors
tools/testing/selftests/kselftest_harness.h | 113 +++++++++++++-----
tools/testing/selftests/landlock/fs_test.c | 83 ++++++++-----
tools/testing/selftests/pidfd/config | 2 +
.../selftests/pidfd/pidfd_setns_test.c | 2 +-
4 files changed, 135 insertions(+), 65 deletions(-)
base-commit: c942a0cd3603e34dd2d7237e064d9318cb7f9654
--
2.44.0
Fix a race condition when running several FIXTURE_TEARDOWN() managing
the same resource. This fixes a race condition in the Landlock file
system tests when creating or unmounting the same directory.
Using clone3() with CLONE_VFORK guarantees that the child and grandchild
test processes are sequentially scheduled. This is implemented with a
new clone3_vfork() helper replacing the fork() call.
This avoids triggering this error in __wait_for_test():
Test ended in some other way [127]
Cc: Christian Brauner <[email protected]>
Cc: David S. Miller <[email protected]>
Cc: Günther Noack <[email protected]>
Cc: Jakub Kicinski <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Mark Brown <[email protected]>
Cc: Shuah Khan <[email protected]>
Cc: Will Drewry <[email protected]>
Fixes: 41cca0542d7c ("selftests/harness: Fix TEST_F()'s vfork handling")
Signed-off-by: Mickaël Salaün <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
---
tools/testing/selftests/kselftest_harness.h | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/tools/testing/selftests/kselftest_harness.h b/tools/testing/selftests/kselftest_harness.h
index 73491efbae9e..d2dd246a3843 100644
--- a/tools/testing/selftests/kselftest_harness.h
+++ b/tools/testing/selftests/kselftest_harness.h
@@ -67,6 +67,8 @@
#include <sys/wait.h>
#include <unistd.h>
#include <setjmp.h>
+#include <syscall.h>
+#include <linux/sched.h>
#include "kselftest.h"
@@ -81,6 +83,17 @@
# define TH_LOG_ENABLED 1
#endif
+/* Wait for the child process to end but without sharing memory mapping. */
+static pid_t __attribute__((__unused__)) clone3_vfork(void)
+{
+ struct clone_args args = {
+ .flags = CLONE_VFORK,
+ .exit_signal = SIGCHLD,
+ };
+
+ return syscall(__NR_clone3, &args, sizeof(args));
+}
+
/**
* TH_LOG()
*
@@ -1180,7 +1193,7 @@ void __run_test(struct __fixture_metadata *f,
fflush(stdout);
fflush(stderr);
- t->pid = fork();
+ t->pid = clone3_vfork();
if (t->pid < 0) {
ksft_print_msg("ERROR SPAWNING TEST CHILD\n");
t->exit_code = KSFT_FAIL;
--
2.44.0