diff mbox series

[v1,5/8] kunit: Handle test faults

Message ID 20240229170409.365386-6-mic@digikod.net
State New
Headers
Series Run KUnit tests late and handle faults |

Commit Message

Mickaël Salaün Feb. 29, 2024, 5:04 p.m. UTC 
  Previously, when a kernel test thread crashed (e.g. NULL pointer
dereference, general protection fault), the KUnit test hanged for 30
seconds and exited with a timeout error.

Fix this issue by waiting on task_struct->vfork_done instead of the
custom kunit_try_catch.try_completion, and track the execution state by
initially setting try_result with -EFAULT and only setting it to 0 if
the test passed.

Fix kunit_generic_run_threadfn_adapter() signature by returning 0
instead of calling kthread_complete_and_exit().  Because thread's exit
code is never checked, always set it to 0 to make it clear.

Fix the -EINTR error message, which couldn't be reached until now.

This is tested with a following patch.

Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: David Gow <davidgow@google.com>
Cc: Rae Moar <rmoar@google.com>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
---
 include/kunit/try-catch.h |  3 ---
 lib/kunit/try-catch.c     | 14 +++++++-------
 2 files changed, 7 insertions(+), 10 deletions(-)

Comments

Kees Cook Feb. 29, 2024, 6:24 p.m. UTC | #1 
On Thu, Feb 29, 2024 at 06:04:06PM +0100, Mickaël Salaün wrote:
> Previously, when a kernel test thread crashed (e.g. NULL pointer
> dereference, general protection fault), the KUnit test hanged for 30
> seconds and exited with a timeout error.
> 
> Fix this issue by waiting on task_struct->vfork_done instead of the
> custom kunit_try_catch.try_completion, and track the execution state by
> initially setting try_result with -EFAULT and only setting it to 0 if
> the test passed.
> 
> Fix kunit_generic_run_threadfn_adapter() signature by returning 0
> instead of calling kthread_complete_and_exit().  Because thread's exit
> code is never checked, always set it to 0 to make it clear.
> 
> Fix the -EINTR error message, which couldn't be reached until now.
> 
> This is tested with a following patch.
> 
> Cc: Brendan Higgins <brendanhiggins@google.com>
> Cc: David Gow <davidgow@google.com>
> Cc: Rae Moar <rmoar@google.com>
> Cc: Shuah Khan <skhan@linuxfoundation.org>
> Signed-off-by: Mickaël Salaün <mic@digikod.net>

I assume we can start checking for "intentional" faults now?

Reviewed-by: Kees Cook <keescook@chromium.org>
Mickaël Salaün March 1, 2024, 7:09 p.m. UTC | #2 
On Thu, Feb 29, 2024 at 10:24:19AM -0800, Kees Cook wrote:
> On Thu, Feb 29, 2024 at 06:04:06PM +0100, Mickaël Salaün wrote:
> > Previously, when a kernel test thread crashed (e.g. NULL pointer
> > dereference, general protection fault), the KUnit test hanged for 30
> > seconds and exited with a timeout error.
> > 
> > Fix this issue by waiting on task_struct->vfork_done instead of the
> > custom kunit_try_catch.try_completion, and track the execution state by
> > initially setting try_result with -EFAULT and only setting it to 0 if
> > the test passed.
> > 
> > Fix kunit_generic_run_threadfn_adapter() signature by returning 0
> > instead of calling kthread_complete_and_exit().  Because thread's exit
> > code is never checked, always set it to 0 to make it clear.
> > 
> > Fix the -EINTR error message, which couldn't be reached until now.
> > 
> > This is tested with a following patch.
> > 
> > Cc: Brendan Higgins <brendanhiggins@google.com>
> > Cc: David Gow <davidgow@google.com>
> > Cc: Rae Moar <rmoar@google.com>
> > Cc: Shuah Khan <skhan@linuxfoundation.org>
> > Signed-off-by: Mickaël Salaün <mic@digikod.net>
> 
> I assume we can start checking for "intentional" faults now?

Yes, but adding dedicated exception handling for such faults would
probably be cleaner.

At least we can now easily write tests as I did with the last patch. The
only potential issue is that the kernel will still print the related
warning in logs, but I think it's OK for tests (and maybe something we'd
like to test too by the way).

> 
> Reviewed-by: Kees Cook <keescook@chromium.org>
> 
> -- 
> Kees Cook
>
diff mbox series

Patch

diff --git a/include/kunit/try-catch.h b/include/kunit/try-catch.h
index c507dd43119d..7c966a1adbd3 100644
--- a/include/kunit/try-catch.h
+++ b/include/kunit/try-catch.h
@@ -14,13 +14,11 @@ 
 
 typedef void (*kunit_try_catch_func_t)(void *);
 
-struct completion;
 struct kunit;
 
 /**
  * struct kunit_try_catch - provides a generic way to run code which might fail.
  * @test: The test case that is currently being executed.
- * @try_completion: Completion that the control thread waits on while test runs.
  * @try_result: Contains any errno obtained while running test case.
  * @try: The function, the test case, to attempt to run.
  * @catch: The function called if @try bails out.
@@ -46,7 +44,6 @@  struct kunit;
 struct kunit_try_catch {
 	/* private: internal use only. */
 	struct kunit *test;
-	struct completion *try_completion;
 	int try_result;
 	kunit_try_catch_func_t try;
 	kunit_try_catch_func_t catch;
diff --git a/lib/kunit/try-catch.c b/lib/kunit/try-catch.c
index cab8b24b5d5a..c6ee4db0b3bd 100644
--- a/lib/kunit/try-catch.c
+++ b/lib/kunit/try-catch.c
@@ -18,7 +18,7 @@ 
 void __noreturn kunit_try_catch_throw(struct kunit_try_catch *try_catch)
 {
 	try_catch->try_result = -EFAULT;
-	kthread_complete_and_exit(try_catch->try_completion, -EFAULT);
+	kthread_exit(0);
 }
 EXPORT_SYMBOL_GPL(kunit_try_catch_throw);
 
@@ -26,9 +26,12 @@  static int kunit_generic_run_threadfn_adapter(void *data)
 {
 	struct kunit_try_catch *try_catch = data;
 
+	try_catch->try_result = -EINTR;
 	try_catch->try(try_catch->context);
+	if (try_catch->try_result == -EINTR)
+		try_catch->try_result = 0;
 
-	kthread_complete_and_exit(try_catch->try_completion, 0);
+	return 0;
 }
 
 static unsigned long kunit_test_timeout(void)
@@ -58,13 +61,11 @@  static unsigned long kunit_test_timeout(void)
 
 void kunit_try_catch_run(struct kunit_try_catch *try_catch, void *context)
 {
-	DECLARE_COMPLETION_ONSTACK(try_completion);
 	struct kunit *test = try_catch->test;
 	struct task_struct *task_struct;
 	int exit_code, time_remaining;
 
 	try_catch->context = context;
-	try_catch->try_completion = &try_completion;
 	try_catch->try_result = 0;
 	task_struct = kthread_create(kunit_generic_run_threadfn_adapter,
 				     try_catch, "kunit_try_catch_thread");
@@ -75,8 +76,7 @@  void kunit_try_catch_run(struct kunit_try_catch *try_catch, void *context)
 	}
 	get_task_struct(task_struct);
 	wake_up_process(task_struct);
-
-	time_remaining = wait_for_completion_timeout(&try_completion,
+	time_remaining = wait_for_completion_timeout(task_struct->vfork_done,
 						     kunit_test_timeout());
 	if (time_remaining == 0) {
 		try_catch->try_result = -ETIMEDOUT;
@@ -92,7 +92,7 @@  void kunit_try_catch_run(struct kunit_try_catch *try_catch, void *context)
 	if (exit_code == -EFAULT)
 		try_catch->try_result = 0;
 	else if (exit_code == -EINTR)
-		kunit_err(test, "wake_up_process() was never called\n");
+		kunit_err(test, "try faulted\n");
 	else if (exit_code == -ETIMEDOUT)
 		kunit_err(test, "try timed out\n");
 	else if (exit_code)