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drm/panfrost: Fix a race in panfrost_gem_free_object() 

panfrost_gem_shrinker_scan() might purge a BO (release the sgt and
kill the GPU mapping) that's being freed by panfrost_gem_free_object()
if we don't remove the BO from the shrinker list at the beginning of
panfrost_gem_free_object().

Fixes: 013b651013 ("drm/panfrost: Add madvise and shrinker support")
Cc: <stable@vger.kernel.org>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Acked-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20191129135908.2439529-5-boris.brezillon@collabora.com
This commit is contained in:
Boris Brezillon 2019-11-29 14:59:04 +01:00 committed by Rob Herring
parent 3bb69dbcb9
commit aed44cbeae
1 changed files with 10 additions and 5 deletions
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15
drivers/gpu/drm/panfrost/panfrost_gem.c
View File

@ -19,6 +19,16 @@ static void panfrost_gem_free_object(struct drm_gem_object *obj)
struct panfrost_gem_object *bo = to_panfrost_bo(obj);
struct panfrost_device *pfdev = obj->dev->dev_private;
/*
* Make sure the BO is no longer inserted in the shrinker list before
* taking care of the destruction itself. If we don't do that we have a
* race condition between this function and what's done in
* panfrost_gem_shrinker_scan().
*/
mutex_lock(&pfdev->shrinker_lock);
list_del_init(&bo->base.madv_list);
mutex_unlock(&pfdev->shrinker_lock);
if (bo->sgts) {
int i;
int n_sgt = bo->base.base.size / SZ_2M;
@ -33,11 +43,6 @@ static void panfrost_gem_free_object(struct drm_gem_object *obj)
kfree(bo->sgts);
}
mutex_lock(&pfdev->shrinker_lock);
if (!list_empty(&bo->base.madv_list))
list_del(&bo->base.madv_list);
mutex_unlock(&pfdev->shrinker_lock);
drm_gem_shmem_free_object(obj);
}