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

[Tvrtko Ursulin]

+ Daniel as reviewer and maybe merge, avoid falling through cracks at least.

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.

> +	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.

> +
>   	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:

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

Regards,

Tvrtko