drm/imagination: take paired job reference

commit 4ba2abe154ef68f9612eee9d6fbfe53a1736b064 upstream.

For paired jobs, have the fragment job take a reference on the
geometry job, so that the geometry job cannot be freed until
the fragment job has finished with it.

The geometry job structure is accessed when the fragment job is being
prepared by the GPU scheduler. Taking the reference prevents the
geometry job being freed until the fragment job no longer requires it.

Fixes a use after free bug detected by KASAN:

[  124.256386] BUG: KASAN: slab-use-after-free in pvr_queue_prepare_job+0x108/0x868 [powervr]
[  124.264893] Read of size 1 at addr ffff0000084cb960 by task kworker/u16:4/63

Cc: stable@vger.kernel.org
Fixes: eaf01ee5ba28 ("drm/imagination: Implement job submission and scheduling")
Signed-off-by: Brendan King <brendan.king@imgtec.com>
Reviewed-by: Matt Coster <matt.coster@imgtec.com>
Link: https://lore.kernel.org/r/20250318-ddkopsrc-1337-use-after-free-in-pvr_queue_prepare_job-v1-1-80fb30d044a6@imgtec.com
Signed-off-by: Matt Coster <matt.coster@imgtec.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/imagination/pvr_job.c b/drivers/gpu/drm/imagination/pvr_job.c
index 78c2f3c6dce019c6ede3342a0e30783ffd0aa959..6a15c1d2d871d3a8182ad1ff71e949da1cf3d000 100644 (file)
--- a/drivers/gpu/drm/imagination/pvr_job.c
+++ b/drivers/gpu/drm/imagination/pvr_job.c
@@ -684,6 +684,13 @@ pvr_jobs_link_geom_frag(struct pvr_job_data *job_data, u32 *job_count)
                geom_job->paired_job = frag_job;
                frag_job->paired_job = geom_job;
 
+               /* The geometry job pvr_job structure is used when the fragment
+                * job is being prepared by the GPU scheduler. Have the fragment
+                * job hold a reference on the geometry job to prevent it being
+                * freed until the fragment job has finished with it.
+                */
+               pvr_job_get(geom_job);
+
                /* Skip the fragment job we just paired to the geometry job. */
                i++;
        }

diff --git a/drivers/gpu/drm/imagination/pvr_queue.c b/drivers/gpu/drm/imagination/pvr_queue.c
index 87780cc7c0c3225ab182dbbd5e42ef8be7d8f2df..130473cfdfc9b7cc80a058727947eea79d248d36 100644 (file)
--- a/drivers/gpu/drm/imagination/pvr_queue.c
+++ b/drivers/gpu/drm/imagination/pvr_queue.c
@@ -866,6 +866,10 @@ static void pvr_queue_free_job(struct drm_sched_job *sched_job)
        struct pvr_job *job = container_of(sched_job, struct pvr_job, base);
 
        drm_sched_job_cleanup(sched_job);
+
+       if (job->type == DRM_PVR_JOB_TYPE_FRAGMENT && job->paired_job)
+               pvr_job_put(job->paired_job);
+
        job->paired_job = NULL;
        pvr_job_put(job);
 }