On 11.07.2023 12:18, Andi Shyti wrote:
Hi Andrzej, On Thu, Jul 06, 2023 at 05:16:11PM +0200, Andrzej Hajda wrote:GuC virtual engines can be removed before request removal. On the other side driver expects rq->engine to be a valid pointer for a whole life of request. Setting rq->engine to an always valid engine should solve the issue. The patch fixes bug detected by KASAN with following signature: i915 0000:00:02.0: [drm:i915_drop_caches_set [i915]] Dropping caches: 0x0000005c [0x0000005c] BUG: KASAN: slab-use-after-free in i915_fence_release+0x2a2/0x2f0 [i915] Read of size 4 at addr ffff88813ffda6e8 by task kworker/u32:10/157 ... Allocated by task 1184: ... guc_create_virtual+0x4d/0x1160 [i915] i915_gem_create_context+0x11ee/0x18c0 [i915] ... Freed by task 151: ... intel_guc_deregister_done_process_msg+0x324/0x6d0 [i915] ...so the only difference between v1 and v2 is this part of the log?
yes, I forgot to add changelog.
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/7926 Signed-off-by: Andrzej Hajda <andrzej.hajda@xxxxxxxxx> --- drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c index a0e3ef1c65d246..2c877ea5eda6f0 100644 --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c @@ -3461,6 +3461,8 @@ static void guc_prio_fini(struct i915_request *rq, struct intel_context *ce) static void remove_from_context(struct i915_request *rq) { struct intel_context *ce = request_to_scheduling_context(rq); + struct intel_engine_cs *engine; + intel_engine_mask_t tmp; GEM_BUG_ON(intel_context_is_child(ce)); @@ -3478,6 +3480,15 @@ static void remove_from_context(struct i915_request *rq) atomic_dec(&ce->guc_id.ref); i915_request_notify_execute_cb_imm(rq); + + /* + * GuC virtual engine can disappear after this call, so let's assign + * something valid, as driver expects this to be always valid pointer. + */ + for_each_engine_masked(engine, rq->engine->gt, rq->execution_mask, tmp) { + rq->engine = engine;yes... here the context might lose the virtual engine... I wonder whether this is the rigth solution, though. Maybe we should set rq->engine = NULL; and check for NULL? Don't know.
Setting NULL causes occasional null page de-reference in
i915_request_wait_timeout:
mutex_release(&rq->engine->gt->reset.mutex.dep_map, _THIS_IP_)
rq->engine after removing rq from context is (IMHO) used as a set of aliases for gt and i915 (despite rq itself contains the alias to i915).
Regards
Andrzej
Andi+ break; + } } static const struct intel_context_ops guc_context_ops = { -- 2.34.1
