Unverified Commit a86f1890 authored May 11, 2024 by Mickaël Salaün

selftests/harness: Fix interleaved scheduling leading to race conditions



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: 41cca054 ("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>

parent fff37bd3

tools/testing/selftests/kselftest_harness.h

+14 −1

Original line number	Diff line number	Diff line
		@@ -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;