[PATCH v3 6/6] drm/v3d: Protect per-fd reset counter against fd release

[Maíra Canal]

The per-fd reset counter tracks GPU resets caused by jobs submitted
through a specific file descriptor. However, there's a race condition
where the file descriptor can be closed while jobs are still running,
leading to potential access to freed memory when updating the reset
counter.

Ensure that the per-fd reset counter is only updated when the file
descriptor is still valid, preventing use-after-free scenarios during
GPU reset handling.

Signed-off-by: Maíra Canal <mca...@igalia.com>
Reviewed-by: Iago Toral Quiroga <ito...@igalia.com>
---
 drivers/gpu/drm/v3d/v3d_sched.c | 30 +++++++++++++++++-------------
 1 file changed, 17 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/v3d/v3d_sched.c b/drivers/gpu/drm/v3d/v3d_sched.c
index 
b8984e608547cf3e3a4f06bd0b8340b804a0f821..0ec06bfbbebb5e6347e72c3e9379e71ea4ba8bc2
 100644
--- a/drivers/gpu/drm/v3d/v3d_sched.c
+++ b/drivers/gpu/drm/v3d/v3d_sched.c
@@ -722,17 +722,19 @@ v3d_cache_clean_job_run(struct drm_sched_job *sched_job)
 }
 
 static enum drm_gpu_sched_stat
-v3d_gpu_reset_for_timeout(struct v3d_dev *v3d, struct drm_sched_job *sched_job)
+v3d_gpu_reset_for_timeout(struct v3d_dev *v3d, struct drm_sched_job *sched_job,
+                         enum v3d_queue q)
 {
        struct v3d_job *job = to_v3d_job(sched_job);
        struct v3d_file_priv *v3d_priv = job->file_priv;
-       enum v3d_queue q;
+       unsigned long irqflags;
+       enum v3d_queue i;
 
        mutex_lock(&v3d->reset_lock);
 
        /* block scheduler */
-       for (q = 0; q < V3D_MAX_QUEUES; q++)
-               drm_sched_stop(&v3d->queue[q].sched, sched_job);
+       for (i = 0; i < V3D_MAX_QUEUES; i++)
+               drm_sched_stop(&v3d->queue[i].sched, sched_job);
 
        if (sched_job)
                drm_sched_increase_karma(sched_job);
@@ -741,15 +743,17 @@ v3d_gpu_reset_for_timeout(struct v3d_dev *v3d, struct 
drm_sched_job *sched_job)
        v3d_reset(v3d);
 
        v3d->reset_counter++;
-       v3d_priv->reset_counter++;
+       spin_lock_irqsave(&v3d->queue[q].queue_lock, irqflags);
+       if (v3d_priv)
+               v3d_priv->reset_counter++;
+       spin_unlock_irqrestore(&v3d->queue[q].queue_lock, irqflags);
 
-       for (q = 0; q < V3D_MAX_QUEUES; q++)
-               drm_sched_resubmit_jobs(&v3d->queue[q].sched);
+       for (i = 0; i < V3D_MAX_QUEUES; i++)
+               drm_sched_resubmit_jobs(&v3d->queue[i].sched);
 
        /* Unblock schedulers and restart their jobs. */
-       for (q = 0; q < V3D_MAX_QUEUES; q++) {
-               drm_sched_start(&v3d->queue[q].sched, 0);
-       }
+       for (i = 0; i < V3D_MAX_QUEUES; i++)
+               drm_sched_start(&v3d->queue[i].sched, 0);
 
        mutex_unlock(&v3d->reset_lock);
 
@@ -777,7 +781,7 @@ v3d_cl_job_timedout(struct drm_sched_job *sched_job, enum 
v3d_queue q,
                return DRM_GPU_SCHED_STAT_NO_HANG;
        }
 
-       return v3d_gpu_reset_for_timeout(v3d, sched_job);
+       return v3d_gpu_reset_for_timeout(v3d, sched_job, q);
 }
 
 static enum drm_gpu_sched_stat
@@ -803,7 +807,7 @@ v3d_tfu_job_timedout(struct drm_sched_job *sched_job)
 {
        struct v3d_job *job = to_v3d_job(sched_job);
 
-       return v3d_gpu_reset_for_timeout(job->v3d, sched_job);
+       return v3d_gpu_reset_for_timeout(job->v3d, sched_job, V3D_TFU);
 }
 
 static enum drm_gpu_sched_stat
@@ -822,7 +826,7 @@ v3d_csd_job_timedout(struct drm_sched_job *sched_job)
                return DRM_GPU_SCHED_STAT_NO_HANG;
        }
 
-       return v3d_gpu_reset_for_timeout(v3d, sched_job);
+       return v3d_gpu_reset_for_timeout(v3d, sched_job, V3D_CSD);
 }
 
 static const struct drm_sched_backend_ops v3d_bin_sched_ops = {

-- 
2.51.0