Re: [PATCH v5] drm/i915: Fix NULL pointer dereference in capture_engine

[Jani Nikula <jani.nikula@linux.intel.com>]

On Tue, 03 Dec 2024, Eugene Kobyak <eugene.kobyak@intel.com> wrote:
> When the intel_context structure contains NULL,
> it raises a NULL pointer dereference error in drm_info().

Blank line here between commit message body and trailers.

> Fixes: e8a3319c31a1 ("drm/i915: Allow error capture without a request")
> Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/12309
> Cc: John Harrison <John.C.Harrison@Intel.com>
> Cc: <stable@vger.kernel.org> # v6.3+
> Signed-off-by: Eugene Kobyak <eugene.kobyak@intel.com>
> ---
> v2:
>   - return drm_info to separate condition
> v3:
>   - create separate condition which generate string if intel_context exist
> v4:
>   - rollback and add check intel_context in log condition
> v5:
>   - create separate string with guc_id if intel_context exist
>  drivers/gpu/drm/i915/i915_gpu_error.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
> index 135ded17334e..4ca6b9872a48 100644
> --- a/drivers/gpu/drm/i915/i915_gpu_error.c
> +++ b/drivers/gpu/drm/i915/i915_gpu_error.c
> @@ -1643,9 +1643,12 @@ capture_engine(struct intel_engine_cs *engine,
>  		return NULL;
>  
>  	intel_engine_get_hung_entity(engine, &ce, &rq);
> -	if (rq && !i915_request_started(rq))
> -		drm_info(&engine->gt->i915->drm, "Got hung context on %s with active request %lld:%lld [0x%04X] not yet started\n",
> -			 engine->name, rq->fence.context, rq->fence.seqno, ce->guc_id.id);
> +	if (rq && !i915_request_started(rq)) {
> +	        char guc_id[11];
> +		ce ? snprintf(guc_id, sizeof(guc_id), " [0x%04x] ", ce->guc_id.id) : snprintf(guc_id, sizeof(guc_id), " ");

I don't know if there's a separate coding style entry saying you
shouldn't use a ternary operator like that, but you shouldn't use a
ternary operator like that.

BR,
Jani.

> +	        drm_info(&engine->gt->i915->drm, "Got hung context on %s with active request %lld:%lld%snot yet started\n",
> +	                 engine->name, rq->fence.context, rq->fence.seqno, guc_id);
> +	}
>  
>  	if (rq) {
>  		capture = intel_engine_coredump_add_request(ee, rq, ATOMIC_MAYFAIL);

-- 
Jani Nikula, Intel