Re: [Intel-gfx] [PATCH 19/27] drm/i915: Fix bug in user proto-context creation that leaked contexts

John Harrison
2021-09-20T22:57:16Z

On 8/20/2021 15:44, Matthew Brost wrote:
> Set number of engines before attempting to create contexts so the
> function free_engines can clean up properly.
>
> Fixes: d4433c7600f7 ("drm/i915/gem: Use the proto-context to handle create parameters (v5)")
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> Cc: <stable@vger.kernel.org>
> ---
> drivers/gpu/drm/i915/gem/i915_gem_context.c | 2 +-
> 1 file changed, 1 insertion(+), 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 dbaeb924a437..bcaaf514876b 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> @@ -944,6 +944,7 @@ static struct i915_gem_engines *user_engines(struct i915_gem_context *ctx,
> unsigned int n;
>
> e = alloc_engines(num_engines);
This can return null when out of memory. There needs to be an early exit
check before dereferencing a null pointer. Not sure if that is a worse
bug or not than leaking memory! Either way, it would be good to fix that
too.

John.

> + e->num_engines = num_engines;
> for (n = 0; n < num_engines; n++) {
> struct intel_context *ce;
> int ret;
> @@ -977,7 +978,6 @@ static struct i915_gem_engines *user_engines(struct i915_gem_context *ctx,
> goto free_engines;
> }
> }
> - e->num_engines = num_engines;
>
> return e;
>