[PATCH] drm/panfrost: Job should reference MMU not file_priv

[Steven Price]

For a while now it's been allowed for a MMU context to outlive it's
corresponding panfrost_priv, however the job structure still references
panfrost_priv to get hold of the MMU context. If panfrost_priv has been
freed this is a use-after-free which I've been able to trigger resulting
in a splat.

To fix this, drop the reference to panfrost_priv in the job structure
and add a direct reference to the MMU structure which is what's actually
needed.

Fixes: 7fdc48cc63a3 ("drm/panfrost: Make sure MMU context lifetime is not bound 
to panfrost_priv")
Signed-off-by: Steven Price <steven.pr...@arm.com>
---
 drivers/gpu/drm/panfrost/panfrost_drv.c | 5 +++--
 drivers/gpu/drm/panfrost/panfrost_job.c | 6 +++---
 drivers/gpu/drm/panfrost/panfrost_job.h | 2 +-
 3 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c 
b/drivers/gpu/drm/panfrost/panfrost_drv.c
index 7fcbc2a5b6cd..087e69b98d06 100644
--- a/drivers/gpu/drm/panfrost/panfrost_drv.c
+++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
@@ -233,6 +233,7 @@ static int panfrost_ioctl_submit(struct drm_device *dev, 
void *data,
                struct drm_file *file)
 {
        struct panfrost_device *pfdev = dev->dev_private;
+       struct panfrost_file_priv *file_priv = file->driver_priv;
        struct drm_panfrost_submit *args = data;
        struct drm_syncobj *sync_out = NULL;
        struct panfrost_job *job;
@@ -262,12 +263,12 @@ static int panfrost_ioctl_submit(struct drm_device *dev, 
void *data,
        job->jc = args->jc;
        job->requirements = args->requirements;
        job->flush_id = panfrost_gpu_get_latest_flush_id(pfdev);
-       job->file_priv = file->driver_priv;
+       job->mmu = file_priv->mmu;
 
        slot = panfrost_job_get_slot(job);
 
        ret = drm_sched_job_init(&job->base,
-                                &job->file_priv->sched_entity[slot],
+                                &file_priv->sched_entity[slot],
                                 NULL);
        if (ret)
                goto out_put_job;
diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c 
b/drivers/gpu/drm/panfrost/panfrost_job.c
index fda5871aebe3..7c4208476fbd 100644
--- a/drivers/gpu/drm/panfrost/panfrost_job.c
+++ b/drivers/gpu/drm/panfrost/panfrost_job.c
@@ -201,7 +201,7 @@ static void panfrost_job_hw_submit(struct panfrost_job 
*job, int js)
                return;
        }
 
-       cfg = panfrost_mmu_as_get(pfdev, job->file_priv->mmu);
+       cfg = panfrost_mmu_as_get(pfdev, job->mmu);
 
        job_write(pfdev, JS_HEAD_NEXT_LO(js), lower_32_bits(jc_head));
        job_write(pfdev, JS_HEAD_NEXT_HI(js), upper_32_bits(jc_head));
@@ -435,7 +435,7 @@ static void panfrost_job_handle_err(struct panfrost_device 
*pfdev,
                job->jc = 0;
        }
 
-       panfrost_mmu_as_put(pfdev, job->file_priv->mmu);
+       panfrost_mmu_as_put(pfdev, job->mmu);
        panfrost_devfreq_record_idle(&pfdev->pfdevfreq);
 
        if (signal_fence)
@@ -456,7 +456,7 @@ static void panfrost_job_handle_done(struct panfrost_device 
*pfdev,
         * happen when we receive the DONE interrupt while doing a GPU reset).
         */
        job->jc = 0;
-       panfrost_mmu_as_put(pfdev, job->file_priv->mmu);
+       panfrost_mmu_as_put(pfdev, job->mmu);
        panfrost_devfreq_record_idle(&pfdev->pfdevfreq);
 
        dma_fence_signal_locked(job->done_fence);
diff --git a/drivers/gpu/drm/panfrost/panfrost_job.h 
b/drivers/gpu/drm/panfrost/panfrost_job.h
index 77e6d0e6f612..8becc1ba0eb9 100644
--- a/drivers/gpu/drm/panfrost/panfrost_job.h
+++ b/drivers/gpu/drm/panfrost/panfrost_job.h
@@ -17,7 +17,7 @@ struct panfrost_job {
        struct kref refcount;
 
        struct panfrost_device *pfdev;
-       struct panfrost_file_priv *file_priv;
+       struct panfrost_mmu *mmu;
 
        /* Fence to be signaled by IRQ handler when the job is complete. */
        struct dma_fence *done_fence;
-- 
2.30.2