linux-kernel - [PATCH] drm/sched: fix potential page fault in drm_sched_job

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Message-ID: <20231108022716.15250-1-dakr@redhat.com>
Date:   Wed,  8 Nov 2023 03:26:07 +0100
From:   Danilo Krummrich <dakr@...hat.com>
To:     airlied@...il.com, daniel@...ll.ch, christian.koenig@....com,
        luben.tuikov@....com
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Danilo Krummrich <dakr@...hat.com>
Subject: [PATCH] drm/sched: fix potential page fault in drm_sched_job_init()

Commit 56e449603f0a ("drm/sched: Convert the GPU scheduler to variable
number of run-queues") introduces drm_err() in drm_sched_job_init(), in
order to indicate that the given entity has no runq, however at this
time job->sched is not yet set, likely to be NULL initialized, and hence
shouldn't be used.

Replace the corresponding drm_err() call with pr_err() to avoid a
potential page fault.

While at it, extend the documentation of drm_sched_job_init() to
indicate that job->sched is not a valid pointer until
drm_sched_job_arm() has been called.

Fixes: 56e449603f0a ("drm/sched: Convert the GPU scheduler to variable number of run-queues")
Signed-off-by: Danilo Krummrich <dakr@...hat.com>
---
 drivers/gpu/drm/scheduler/sched_main.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index 27843e37d9b7..dd28389f0ddd 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -680,6 +680,9 @@ EXPORT_SYMBOL(drm_sched_resubmit_jobs);
  * This function returns -ENOENT in this case (which probably should be -EIO as
  * a more meanigful return value).
  *
+ * Note that job->sched is not a valid pointer until drm_sched_job_arm() has
+ * been called.
+ *
  * Returns 0 for success, negative error code otherwise.
  */
 int drm_sched_job_init(struct drm_sched_job *job,
@@ -691,7 +694,7 @@ int drm_sched_job_init(struct drm_sched_job *job,
 		 * or worse--a blank screen--leave a trail in the
 		 * logs, so this can be debugged easier.
 		 */
-		drm_err(job->sched, "%s: entity has no rq!\n", __func__);
+		pr_err("%s: entity has no rq!\n", __func__);
 		return -ENOENT;
 	}
 

base-commit: c015fb6d01adb616fb54824feb55ce5ab18e8ca1
-- 
2.41.0