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selftests/harness: Fix interleaved scheduling leading to race conditions

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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: 41cca0542d ("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>
This commit is contained in:
Mickaël Salaün 2024-05-11 19:14:39 +02:00
parent fff37bd32c
commit a86f18903d
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1 changed files with 14 additions and 1 deletions
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15
tools/testing/selftests/kselftest_harness.h
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@ -66,6 +66,8 @@
#include <sys/wait.h>
#include <unistd.h>
#include <setjmp.h>
#include <syscall.h>
#include <linux/sched.h>
#include "kselftest.h"
@ -80,6 +82,17 @@
# 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()
*
@ -1183,7 +1196,7 @@ 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;