[Intel-gfx] [PATCH] drm/i915: Fix bug in user proto-context creation that leaked contexts

[Matthew Brost]

On Fri, Oct 01, 2021 at 09:40:19AM +0100, Tvrtko Ursulin wrote:
> 
> + Daniel as reviewer and maybe merge, avoid falling through cracks at least.
> 

Ty, working on push rights myself.

> On 22/09/2021 20:43, Matthew Brost wrote:
> > Set number of engines before attempting to create contexts so the
> > function free_engines can clean up properly. Also check return of
> > alloc_engines for NULL.
> > 
> > v2:
> >   (Tvrtko)
> >    - Send as stand alone patch
> >   (John Harrison)
> >    - Check for alloc_engines returning NULL
> > 
> > Cc: Jason Ekstrand <jason at jlekstrand.net>
> > Fixes: d4433c7600f7 ("drm/i915/gem: Use the proto-context to handle create parameters (v5)")
> > Signed-off-by: Matthew Brost <matthew.brost at intel.com>
> > Cc: <stable at vger.kernel.org>
> > ---
> >   drivers/gpu/drm/i915/gem/i915_gem_context.c | 6 +++++-
> >   1 file changed, 5 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> > index c2ab0e22db0a..9627c7aac6a3 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> > @@ -898,6 +898,11 @@ static struct i915_gem_engines *user_engines(struct i915_gem_context *ctx,
> >   	unsigned int n;
> >   	e = alloc_engines(num_engines);
> > +	if (!e) {
> > +		return ERR_PTR(-ENOMEM);
> > +	}
> 
> Ideally remove the braces and respin.
>

Yep, checkpatch didn't like this. Will respin.
 
> > +	e->num_engines = num_engines;
> 
> Theoretically you could have put it next to "e->engines[n] = ce" assignment
> so the pattern is the same as in default_engines(). Kind of makes more sense
> that the number is not set before anything is created, but as it doesn't
> really matter since free_engines handles sparse arrays so there is argument
> to have a simpler single assignment as well.
>

I like a single assignment, let's not overthink this.
 
> > +
> >   	for (n = 0; n < num_engines; n++) {
> >   		struct intel_context *ce;
> >   		int ret;
> > @@ -931,7 +936,6 @@ static struct i915_gem_engines *user_engines(struct i915_gem_context *ctx,
> >   			goto free_engines;
> >   		}
> >   	}
> > -	e->num_engines = num_engines;
> >   	return e;
> > 
> 
> Fix looks good to me. I did not want to butt in but since more than a week
> has passed without it getting noticed:
> 

Again, ty.

Matt

> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> 
> Regards,
> 
> Tvrtko