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 <brauner@kernel.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Günther Noack <gnoack@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Will Drewry <wad@chromium.org>
Fixes: 41cca0542d7c ("selftests/harness: Fix TEST_F()'s vfork handling")
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20240511171445.904356-5-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
#include <sys/wait.h>
#include <unistd.h>
#include <setjmp.h>
+#include <syscall.h>
+#include <linux/sched.h>
#include "kselftest.h"
# define TH_LOG_ENABLED 1
#endif
+/* Wait for the child process to end but without sharing memory mapping. */
+static inline pid_t clone3_vfork(void)
+{
+ struct clone_args args = {
+ .flags = CLONE_VFORK,
+ .exit_signal = SIGCHLD,
+ };
+
+ return syscall(__NR_clone3, &args, sizeof(args));
+}
+
/**
* TH_LOG()
*
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;