From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mout-p-101.mailbox.org (mout-p-101.mailbox.org [80.241.56.151]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 28A3F2848AA for ; Tue, 2 Sep 2025 11:54:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=80.241.56.151 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756814055; cv=none; b=FfZu5mr6zfRhK7J11dvIS5gQSDwiLJWhS+NpYaOSAf8xDGRqVRaBZHfs9sE/5e4IOcQdSKT1B1HgCLmZjtuJyorjxWDhf9sRTE4+x38f5DaydRTbWgIAN8lRihlmxPJRwoZ67Awrm2CsLG2baJoqHN8bfnCbqH4iXWZ/KIv3iIA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756814055; c=relaxed/simple; bh=A3oYmGMRkstL2rktDLFWJEbetTQIeAZ0cKssgdD76C0=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=qcxiSvCanl1A8KXa9hDVRsHKHBFJx58y/1LO4of9UPv+9jXZRYddTFbte1e5QzCVsSI/gKXdgJneX0iCVSFmHKX8PyMNQQhFpxk/2kzfFr72JyG6W2Pp20b+N14qihr0cPBsWU+YtMl07L2P8InozvvO+9/IzLOG7rSEdjWil4I= ARC-Authentication-Results:i=1; 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s=mail20150812; t=1756814048; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=CQfOullEKJbtvzY93DucdIHN8FLO7u/qthSzwSFy9vY=; b=rTEFP3IhcEDcVCKEjC5sR0s5bQ98CVeCGFYfUfjXo02gK9IHf00Hy1WOb8Cl/6dbDQTvf8 aU6bDns+h/UP0BSx8buaioiXnuDHPkDK217eACCfdIxVTROTteaVyIOuwf+ASPL+mArPIe KNWe8aHo9fUnd1EnmO2Qt53sH62Y5YM4rYq8q8cXucJpwM7CqFbfxC+L2xtHuy6Brs5pOs 9PgPDg1K4ga4+tlu5HZTINpLIbp06aUItBpa0RuX1AhFQwZpuEJEF8wSlPeW2P7DqHs+SL qiISZS+J3ATfBvVVtsuu1pjByNlOSNvavaPXyQawYgG+ZtKAPiss8R6OvsA1Og== Message-ID: <3ac127e7ae0c71c354eead23a77d2006bde42692.camel@mailbox.org> Subject: Re: [PATCH v2] drm/sched: Fix racy access to drm_sched_entity.dependency From: Philipp Stanner Reply-To: phasta@kernel.org To: phasta@kernel.org, Tvrtko Ursulin , Pierre-Eric Pelloux-Prayer , Matthew Brost , Danilo Krummrich , Christian =?ISO-8859-1?Q?K=F6nig?= , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Date: Tue, 02 Sep 2025 13:54:02 +0200 In-Reply-To: References: <20250901124032.1955-1-pierre-eric.pelloux-prayer@amd.com> <22e70ef7472310ad5147f934044a7ba0e02e02d6.camel@mailbox.org> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MBO-RS-META: d14s54ed9xbycoz7nw4dyh9twrrtknpx X-MBO-RS-ID: cc990f10a1ae4e576e8 On Tue, 2025-09-02 at 10:22 +0200, Philipp Stanner wrote: > On Tue, 2025-09-02 at 10:18 +0200, Philipp Stanner wrote: > > On Tue, 2025-09-02 at 08:59 +0100, Tvrtko Ursulin wrote: > > >=20 > > > On 02/09/2025 08:27, Philipp Stanner wrote: > > > > On Mon, 2025-09-01 at 14:40 +0200, Pierre-Eric Pelloux-Prayer wrote= : > > > > > The drm_sched_job_unschedulable trace point can access > > > > > entity->dependency after it was cleared by the callback > > > > > installed in drm_sched_entity_add_dependency_cb, causing: > > > > >=20 > > > > > BUG: kernel NULL pointer dereference, address: 0000000000000020 > > > > > [...] > > > > > Workqueue: comp_1.1.0 drm_sched_run_job_work [gpu_sched] > > > > > RIP: 0010:trace_event_raw_event_drm_sched_job_unschedulable+0x70/= 0xd0 [gpu_sched] > > > > >=20 > > > > > To fix this we either need to keep a reference to the fence befor= e > > > > > setting up the callbacks, or move the trace_drm_sched_job_unsched= ulable > > > > > calls into drm_sched_entity_add_dependency_cb where they can be > > > > > done earlier. > > > > >=20 > > > > > Fixes: 76d97c870f29 ("drm/sched: Trace dependencies for GPU jobs"= ) > > > > >=20 > > > > > Signed-off-by: Pierre-Eric Pelloux-Prayer > > > > > Reviewed-by: Tvrtko Ursulin > > > >=20 > > > > Applied to drm-misc-next > > >=20 > > > Shouldn't it have been drm-misc-fixes? > >=20 > > I considered that, but thought not: the fixed commit is only in this rc > > (v6.17), and in this case the committer guidelines say it should go to > > misc-next: > >=20 > > https://drm.pages.freedesktop.org/maintainer-tools/committer/committer-= drm-misc.html >=20 > OK, wait, the opposite is the case. I slipped to the wrong branch in > the diagram. >=20 > Oh dear. My coffee machine broke a few days ago, and it shows. >=20 > My bad, sorry. Let me ping the drm maintainers to sort that one out. Maxime was so kind to fix this for me. Merci, Maxime, and sorry guys. Is now on drm-misc-fixes and we're good. P. >=20 > P. >=20 >=20 >=20 > >=20 > > Same reason we don't need to +Cc stable. > >=20 > > But correct me if I made a mistake. > >=20 > > P. > >=20 > >=20 > > >=20 > > > Regards, > > >=20 > > > Tvrtko > > >=20 > > > > > --- > > > > > =C2=A0=C2=A0drivers/gpu/drm/scheduler/sched_entity.c | 11 +++++++= ---- > > > > > =C2=A0=C2=A01 file changed, 7 insertions(+), 4 deletions(-) > > > > >=20 > > > > > diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/g= pu/drm/scheduler/sched_entity.c > > > > > index 8867b95ab089..3d06f72531ba 100644 > > > > > --- a/drivers/gpu/drm/scheduler/sched_entity.c > > > > > +++ b/drivers/gpu/drm/scheduler/sched_entity.c > > > > > @@ -391,7 +391,8 @@ EXPORT_SYMBOL(drm_sched_entity_set_priority); > > > > > =C2=A0=C2=A0 * Add a callback to the current dependency of the en= tity to wake up the > > > > > =C2=A0=C2=A0 * scheduler when the entity becomes available. > > > > > =C2=A0=C2=A0 */ > > > > > -static bool drm_sched_entity_add_dependency_cb(struct drm_sched_= entity *entity) > > > > > +static bool drm_sched_entity_add_dependency_cb(struct drm_sched_= entity *entity, > > > > > + =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 struct drm_sched_job *= sched_job) > > > > > =C2=A0=C2=A0{ > > > > > =C2=A0=C2=A0 struct drm_gpu_scheduler *sched =3D entity->rq->sche= d; > > > > > =C2=A0=C2=A0 struct dma_fence *fence =3D entity->dependency; > > > > > @@ -421,6 +422,10 @@ static bool drm_sched_entity_add_dependency_= cb(struct drm_sched_entity *entity) > > > > > =C2=A0=C2=A0 entity->dependency =3D fence; > > > > > =C2=A0=C2=A0 } > > > > > =C2=A0=20 > > > > > + if (trace_drm_sched_job_unschedulable_enabled() && > > > > > + =C2=A0=C2=A0=C2=A0 !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &enti= ty->dependency->flags)) > > > > > + trace_drm_sched_job_unschedulable(sched_job, entity->dependenc= y); > > > > > + > > > > > =C2=A0=C2=A0 if (!dma_fence_add_callback(entity->dependency, &ent= ity->cb, > > > > > =C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 drm_sched_entity_wakeup)) > > > > > =C2=A0=C2=A0 return true; > > > > > @@ -461,10 +466,8 @@ struct drm_sched_job *drm_sched_entity_pop_j= ob(struct drm_sched_entity *entity) > > > > > =C2=A0=20 > > > > > =C2=A0=C2=A0 while ((entity->dependency =3D > > > > > =C2=A0=C2=A0 drm_sched_job_dependency(sched_job, entity))) { > > > > > - if (drm_sched_entity_add_dependency_cb(entity)) { > > > > > - trace_drm_sched_job_unschedulable(sched_job, entity->dependen= cy); > > > > > + if (drm_sched_entity_add_dependency_cb(entity, sched_job)) > > > > > =C2=A0=C2=A0 return NULL; > > > > > - } > > > > > =C2=A0=C2=A0 } > > > > > =C2=A0=20 > > > > > =C2=A0=C2=A0 /* skip jobs from entity that marked guilty */ > > > >=20 > > >=20 > >=20 >=20