diff mbox series

[v3,4/7] kunit: Handle test faults

Message ID 20240319104857.70783-5-mic@digikod.net (mailing list archive)
State Handled Elsewhere
Headers show
Series Handle faults in KUnit tests | expand

Commit Message

Mickaël Salaün March 19, 2024, 10:48 a.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 -EINTR 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: Shuah Khan <skhan@linuxfoundation.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: David Gow <davidgow@google.com>
Tested-by: Rae Moar <rmoar@google.com>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Link: https://lore.kernel.org/r/20240319104857.70783-5-mic@digikod.net
---

Changes since v2:
* s/-EFAULT/-EINTR/ in commit message as spotted by Rae.
* Add a comment explaining vfork_done as suggested by David.
* Add David's Reviewed-by.
* Add Rae's Tested-by.

Changes since v1:
* Add Kees's Reviewed-by.
---
 include/kunit/try-catch.h |  3 ---
 lib/kunit/try-catch.c     | 19 ++++++++++++-------
 2 files changed, 12 insertions(+), 10 deletions(-)

Comments

David Gow March 23, 2024, 7:37 a.m. UTC | #1
On Tue, 19 Mar 2024 at 18:49, Mickaël Salaün <mic@digikod.net> 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 -EINTR 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: Shuah Khan <skhan@linuxfoundation.org>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Reviewed-by: David Gow <davidgow@google.com>
> Tested-by: Rae Moar <rmoar@google.com>
> Signed-off-by: Mickaël Salaün <mic@digikod.net>
> Link: https://lore.kernel.org/r/20240319104857.70783-5-mic@digikod.net
> ---
>
> Changes since v2:
> * s/-EFAULT/-EINTR/ in commit message as spotted by Rae.
> * Add a comment explaining vfork_done as suggested by David.
> * Add David's Reviewed-by.
> * Add Rae's Tested-by.
>
> Changes since v1:
> * Add Kees's Reviewed-by.
> ---
>  include/kunit/try-catch.h |  3 ---
>  lib/kunit/try-catch.c     | 19 ++++++++++++-------
>  2 files changed, 12 insertions(+), 10 deletions(-)
>
> 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..7a3910dd78a6 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);

It turns out kthread_exit() is not exported, so this doesn't work if
KUnit is built as a module.

I think the options we have are:
- Add EXPORT_SYMBOL(kthread_exit).
- Keep using out own completion, and kthread_complete_and_exit()
- try_get_module() before spawning the thread, and use
module_put_and_kthread_exit().

I think all of these would be okay, but I could've missed something.

-- David

>  }
>  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 +76,12 @@ 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,
> +       /*
> +        * 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,
>                                                      kunit_test_timeout());
>         if (time_remaining == 0) {
>                 try_catch->try_result = -ETIMEDOUT;
> @@ -92,7 +97,7 @@ 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)
> --
> 2.44.0
>
Mickaël Salaün March 26, 2024, 9:02 a.m. UTC | #2
On Sat, Mar 23, 2024 at 03:37:21PM +0800, David Gow wrote:
> On Tue, 19 Mar 2024 at 18:49, Mickaël Salaün <mic@digikod.net> 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 -EINTR 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: Shuah Khan <skhan@linuxfoundation.org>
> > Reviewed-by: Kees Cook <keescook@chromium.org>
> > Reviewed-by: David Gow <davidgow@google.com>
> > Tested-by: Rae Moar <rmoar@google.com>
> > Signed-off-by: Mickaël Salaün <mic@digikod.net>
> > Link: https://lore.kernel.org/r/20240319104857.70783-5-mic@digikod.net
> > ---
> >
> > Changes since v2:
> > * s/-EFAULT/-EINTR/ in commit message as spotted by Rae.
> > * Add a comment explaining vfork_done as suggested by David.
> > * Add David's Reviewed-by.
> > * Add Rae's Tested-by.
> >
> > Changes since v1:
> > * Add Kees's Reviewed-by.
> > ---
> >  include/kunit/try-catch.h |  3 ---
> >  lib/kunit/try-catch.c     | 19 ++++++++++++-------
> >  2 files changed, 12 insertions(+), 10 deletions(-)
> >
> > 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..7a3910dd78a6 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);
> 
> It turns out kthread_exit() is not exported, so this doesn't work if
> KUnit is built as a module.
> 
> I think the options we have are:
> - Add EXPORT_SYMBOL(kthread_exit).

I'll go this way. This should not be an issue because
kthread_complete_and_exit() can already (only) call kthread_exit() if
the completion is NULL, but directly calling kthread_exit() is cleaner.

> - Keep using out own completion, and kthread_complete_and_exit()
> - try_get_module() before spawning the thread, and use
> module_put_and_kthread_exit().
> 
> I think all of these would be okay, but I could've missed something.
> 
> -- David
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..7a3910dd78a6 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 +76,12 @@  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,
+	/*
+	 * 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,
 						     kunit_test_timeout());
 	if (time_remaining == 0) {
 		try_catch->try_result = -ETIMEDOUT;
@@ -92,7 +97,7 @@  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)