Re: [PATCH] drm/xe: Do not dereference NULL job->fence in trace points

[Matthew Brost <matthew.brost@intel.com>]

On Thu, Jun 06, 2024 at 12:21:57AM -0500, Lucas De Marchi wrote:
> On Thu, Jun 06, 2024 at 02:55:23AM GMT, Matthew Brost wrote:
> > On Wed, Jun 05, 2024 at 06:13:42PM -0500, Lucas De Marchi wrote:
> > > On Tue, Jun 04, 2024 at 10:50:41PM GMT, Matthew Brost wrote:
> > > > job->fence is not assigned until xe_sched_job_arm(), check for
> > > > job->fence in xe_sched_job_seqno() so any usage of this function (trace
> > > > points) do not result in NULL ptr dereference. Also check job->fence
> > > > before assigning error in job trace points.
> > > >
> > > > Fixes: 0ac7a2c745e8 drm/xe: ("Don't initialize fences at xe_sched_job_create()")
> > > > Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> > > > Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> > > > ---
> > > > drivers/gpu/drm/xe/xe_sched_job.h | 2 +-
> > > > drivers/gpu/drm/xe/xe_trace.h     | 2 +-
> > > > 2 files changed, 2 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/drivers/gpu/drm/xe/xe_sched_job.h b/drivers/gpu/drm/xe/xe_sched_job.h
> > > > index 002c3b5c0a5c..f362e28455db 100644
> > > > --- a/drivers/gpu/drm/xe/xe_sched_job.h
> > > > +++ b/drivers/gpu/drm/xe/xe_sched_job.h
> > > > @@ -70,7 +70,7 @@ to_xe_sched_job(struct drm_sched_job *drm)
> > > >
> > > > static inline u32 xe_sched_job_seqno(struct xe_sched_job *job)
> > > > {
> > > > -	return job->fence->seqno;
> > > > +	return job->fence ? job->fence->seqno : 0;
> > > > }
> > > >
> > > > static inline u32 xe_sched_job_lrc_seqno(struct xe_sched_job *job)
> > > > diff --git a/drivers/gpu/drm/xe/xe_trace.h b/drivers/gpu/drm/xe/xe_trace.h
> > > > index 450f407c66e8..e4cba64474e6 100644
> > > > --- a/drivers/gpu/drm/xe/xe_trace.h
> > > > +++ b/drivers/gpu/drm/xe/xe_trace.h
> > > > @@ -270,7 +270,7 @@ DECLARE_EVENT_CLASS(xe_sched_job,
> > > > 			   __entry->guc_state =
> > > > 			   atomic_read(&job->q->guc->state);
> > > > 			   __entry->flags = job->q->flags;
> > > > -			   __entry->error = job->fence->error;
> > > > +			   __entry->error = job->fence ? job->fence->error : 0;
> > > 
> > > we already include xe_sched_job.h in this file and even call
> > > xe_sched_job_lrc_seqno() a few lines above this. Why can't we call the
> > > function you just fixed? With that changed,
> > 
> > We do call that function above, it just is not in the diff.
> > 
> > We don't have a helper to go from job -> job->fence->error hence the
> > open coding here. I could add a helper if you like.
> 
> ahh... ok, I misread s/error/seqno/ thinking they were handling the same
> thing.
> 
> let's just merge this as is then.
> 

Merged. Thanks.

Matt

> thanks
> Lucas De Marchi
> 
> > 
> > Matt
> > 
> > > 
> > > 	Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
> > > 
> > > 
> > > Lucas De Marchi
> > > 
> > > > 			   __entry->fence = job->fence;
> > > > 			   __entry->batch_addr = (u64)job->ptrs[0].batch_addr;
> > > > 			   ),
> > > > --
> > > > 2.34.1
> > > >