| Message ID | 20240412025903.489470-1-davidgow@google.com |
|---|---|
| State | New |
| Headers | show |
| Series | kunit: Fix race condition in try-catch completion | expand |
On Thu, Apr 11, 2024 at 10:59 PM David Gow <davidgow@google.com> wrote: > > KUnit's try-catch infrastructure now uses vfork_done, which is always > set to a valid completion when a kthread is created, 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> > Closes: https://lore.kernel.org/lkml/20240410102710.35911-1-naresh.kamboju@linaro.org/ > Tested-by: Linux Kernel Functional Testing <lkft@linaro.org> > Acked-by: Mickaël Salaün <mic@digikod.net> > Signed-off-by: David Gow <davidgow@google.com> I noticed it with the Rust tests too, and indeed this fixed it: Tested-by: Miguel Ojeda <ojeda@kernel.org> Thanks! Cheers, Miguel
diff --git a/lib/kunit/try-catch.c b/lib/kunit/try-catch.c index fa687278ccc9..6bbe0025b079 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 +76,16 @@ void kunit_try_catch_run(struct kunit_try_catch *try_catch, void *context) return; } get_task_struct(task_struct); - 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. + * kernel thread. It is set to NULL when the thread exits, so we + * keep a copy here. */ - time_remaining = wait_for_completion_timeout(task_struct->vfork_done, + task_done = task_struct->vfork_done; + wake_up_process(task_struct); + + time_remaining = wait_for_completion_timeout(task_done, kunit_test_timeout()); if (time_remaining == 0) { try_catch->try_result = -ETIMEDOUT;
KUnit's try-catch infrastructure now uses vfork_done, which is always set to a valid completion when a kthread is created, 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> Closes: https://lore.kernel.org/lkml/20240410102710.35911-1-naresh.kamboju@linaro.org/ Tested-by: Linux Kernel Functional Testing <lkft@linaro.org> Acked-by: Mickaël Salaün <mic@digikod.net> Signed-off-by: David Gow <davidgow@google.com> --- lib/kunit/try-catch.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)