On Thu, 11 Apr 2024 at 09:55, David Gow davidgow@google.com wrote:
On Wed, 10 Apr 2024 at 23:23, Will Deacon will@kernel.org wrote:
On Wed, Apr 10, 2024 at 03:57:10PM +0530, Naresh Kamboju wrote:
Following kernel crash noticed on Linux next-20240410 tag while running kunit testing on qemu-arm64 and qemu-x86_64.
Reported-by: Linux Kernel Functional Testing lkft@linaro.org
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Ok, so 'task_struct->vfork_done' is NULL. Looks like this code was added recently, so adding Mickaël to cc.
Thanks. This looks like a race condition where the KUnit test kthread can terminate before we wait on it.
Mickaël, does this seem like a correct fix to you?
From: David Gow davidgow@google.com Date: Thu, 11 Apr 2024 12:07:47 +0800 Subject: [PATCH] kunit: Fix race condition in try-catch completion
KUnit's try-catch infrastructure now uses vfork_done, which is always set to a valid completion when a kthread is crated, but which is set to NULL once the thread terminates. This creates a race condition, where the kthread exits before we can wait on it.
Keep a copy of vfork_done, which is taken before we wake_up_process() and so valid, and wait on that instead.
Fixes: 4de2a8e4cca4 ("kunit: Handle test faults") Reported-by: Linux Kernel Functional Testing lkft@linaro.org Signed-off-by: David Gow davidgow@google.com
This patch tested on top of Linux next and reported issues fixed.
Tested-by: Linux Kernel Functional Testing lkft@linaro.org
lib/kunit/try-catch.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/lib/kunit/try-catch.c b/lib/kunit/try-catch.c index fa687278ccc9..fc6cd4d7e80f 100644 --- a/lib/kunit/try-catch.c +++ b/lib/kunit/try-catch.c @@ -63,6 +63,7 @@ void kunit_try_catch_run(struct kunit_try_catch *try_catch, void *context) { struct kunit *test = try_catch->test; struct task_struct *task_struct;
struct completion *task_done; int exit_code, time_remaining; try_catch->context = context;
@@ -75,13 +76,14 @@ void kunit_try_catch_run(struct kunit_try_catch *try_catch, void *context) return; } get_task_struct(task_struct);
task_done = task_struct->vfork_done; wake_up_process(task_struct); /* * As for a vfork(2), task_struct->vfork_done (pointing to the * underlying kthread->exited) can be used to wait for the end of a * kernel thread. */
time_remaining = wait_for_completion_timeout(task_struct->vfork_done,
time_remaining = wait_for_completion_timeout(task_done, kunit_test_timeout()); if (time_remaining == 0) { try_catch->try_result = -ETIMEDOUT;
--
-- Linaro LKFT https://lkft.linaro.org