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.or... Tested-by: Linux Kernel Functional Testing lkft@linaro.org Acked-by: Mickaël Salaün mic@digikod.net Signed-off-by: David Gow davidgow@google.com

Hello,

This fix looks good to me. I have tested it and besides the fortify test error discussed in the previous patch series I am happy.

Thanks! -Rae

Reviewed-by: Rae Moar rmoar@google.com

---

lib/kunit/try-catch.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)

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;
  

-- 2.44.0.683.g7961c838ac-goog