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From: "Mickaël Salaün" <mic@digikod.net>
To: Christian Brauner <brauner@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Jakub Kicinski <kuba@kernel.org>,
	Kees Cook <keescook@chromium.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Mark Brown <broonie@kernel.org>, Sasha Levin <sashal@kernel.org>,
	Sean Christopherson <seanjc@google.com>,
	Shengyu Li <shengyu.li.evgeny@gmail.com>,
	Shuah Khan <shuah@kernel.org>,
	Shuah Khan <skhan@linuxfoundation.org>
Cc: "Mickaël Salaün" <mic@digikod.net>,
	"Bagas Sanjaya" <bagasdotme@gmail.com>,
	"Brendan Higgins" <brendanhiggins@google.com>,
	"David Gow" <davidgow@google.com>,
	"David S . Miller" <davem@davemloft.net>,
	"Florian Fainelli" <florian.fainelli@broadcom.com>,
	"Günther Noack" <gnoack@google.com>,
	"Jon Hunter" <jonathanh@nvidia.com>, "Ron Economos" <re@w6rz.net>,
	"Ronald Warsow" <rwarsow@gmx.de>,
	"Stephen Rothwell" <sfr@canb.auug.org.au>,
	"Will Drewry" <wad@chromium.org>,
	"kernel test robot" <oliver.sang@intel.com>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-kselftest@vger.kernel.org, netdev@vger.kernel.org,
	stable@vger.kernel.org
Subject: [PATCH v7 04/10] selftests/harness: Fix interleaved scheduling leading to race conditions
Date: Sat, 11 May 2024 19:14:39 +0200	[thread overview]
Message-ID: <20240511171445.904356-5-mic@digikod.net> (raw)
In-Reply-To: <20240511171445.904356-1-mic@digikod.net>

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>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Link: https://lore.kernel.org/r/20240511171445.904356-5-mic@digikod.net
---

Changes since v2:
* Replace __attribute__((__unused__)) with inline for clone3_vfork()
  (suggested by Kees and Jakub)
---
 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 55699a762c45..9d7178a71c2c 100644
--- a/tools/testing/selftests/kselftest_harness.h
+++ b/tools/testing/selftests/kselftest_harness.h
@@ -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;
-- 
2.45.0


  parent reply	other threads:[~2024-05-11 17:15 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-05-11 17:14 [PATCH v7 00/10] Fix Kselftest's vfork() side effects Mickaël Salaün
2024-05-11 17:14 ` [PATCH v7 01/10] selftests/pidfd: Fix config for pidfd_setns_test Mickaël Salaün
2024-05-11 17:14 ` [PATCH v7 02/10] selftests/landlock: Fix FS tests when run on a private mount point Mickaël Salaün
2024-05-11 17:14 ` [PATCH v7 03/10] selftests/harness: Fix fixture teardown Mickaël Salaün
2024-05-11 17:14 ` Mickaël Salaün [this message]
2024-05-27 19:07   ` [PATCH v7 04/10] selftests/harness: Fix interleaved scheduling leading to race conditions Mark Brown
2024-06-03 16:27     ` Mark Brown
2024-06-03 17:22       ` Mark Brown
2024-06-04 16:06         ` Mickaël Salaün
2024-06-04 16:18           ` Mark Brown
2024-05-11 17:14 ` [PATCH v7 05/10] selftests/landlock: Do not allocate memory in fixture data Mickaël Salaün
2024-05-11 17:14 ` [PATCH v7 06/10] selftests/harness: Constify fixture variants Mickaël Salaün
2024-05-11 17:14 ` [PATCH v7 07/10] selftests/pidfd: Fix wrong expectation Mickaël Salaün
2024-05-11 17:16   ` kernel test robot
2024-05-11 17:14 ` [PATCH v7 08/10] selftests/harness: Share _metadata between forked processes Mickaël Salaün
2024-05-11 17:14 ` [PATCH v7 09/10] selftests/harness: Fix vfork() side effects Mickaël Salaün
2024-05-11 17:14 ` [PATCH v7 10/10] selftests/harness: Handle TEST_F()'s explicit exit codes Mickaël Salaün

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