On 01/11/2020 17:40, Boris Brezillon wrote:

panfrost_ioctl_madvise() and panfrost_gem_purge() acquire the mappings and shmem locks in different orders, thus leading to a potential the mappings lock first.

Fixes: bdefca2d8dc0 ("drm/panfrost: Add the panfrost_gem_mapping concept") Cc: stable@vger.kernel.org Cc: Christian Hewitt christianshewitt@gmail.com Reported-by: Christian Hewitt christianshewitt@gmail.com Signed-off-by: Boris Brezillon boris.brezillon@collabora.com

Reviewed-by: Steven Price steven.price@arm.com

---

drivers/gpu/drm/panfrost/panfrost_gem.c | 4 +--- drivers/gpu/drm/panfrost/panfrost_gem.h | 2 +- drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c | 14 +++++++++++--- 3 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.c b/drivers/gpu/drm/panfrost/panfrost_gem.c index cdf1a8754eba..0c0243eaee81 100644 --- a/drivers/gpu/drm/panfrost/panfrost_gem.c +++ b/drivers/gpu/drm/panfrost/panfrost_gem.c @@ -105,14 +105,12 @@ void panfrost_gem_mapping_put(struct panfrost_gem_mapping *mapping) kref_put(&mapping->refcount, panfrost_gem_mapping_release); }

-void panfrost_gem_teardown_mappings(struct panfrost_gem_object *bo) +void panfrost_gem_teardown_mappings_locked(struct panfrost_gem_object *bo) { struct panfrost_gem_mapping *mapping;

• mutex_lock(&bo->mappings.lock); list_for_each_entry(mapping, &bo->mappings.list, node) panfrost_gem_teardown_mapping(mapping);

• mutex_unlock(&bo->mappings.lock); }

  int panfrost_gem_open(struct drm_gem_object *obj, struct drm_file *file_priv)

diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.h b/drivers/gpu/drm/panfrost/panfrost_gem.h index b3517ff9630c..8088d5fd8480 100644 --- a/drivers/gpu/drm/panfrost/panfrost_gem.h +++ b/drivers/gpu/drm/panfrost/panfrost_gem.h @@ -82,7 +82,7 @@ struct panfrost_gem_mapping * panfrost_gem_mapping_get(struct panfrost_gem_object *bo, struct panfrost_file_priv *priv); void panfrost_gem_mapping_put(struct panfrost_gem_mapping *mapping); -void panfrost_gem_teardown_mappings(struct panfrost_gem_object *bo); +void panfrost_gem_teardown_mappings_locked(struct panfrost_gem_object *bo);

void panfrost_gem_shrinker_init(struct drm_device *dev); void panfrost_gem_shrinker_cleanup(struct drm_device *dev); diff --git a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c index 288e46c40673..1b9f68d8e9aa 100644 --- a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c +++ b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c @@ -40,18 +40,26 @@ static bool panfrost_gem_purge(struct drm_gem_object *obj) { struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj); struct panfrost_gem_object *bo = to_panfrost_bo(obj);

• bool ret = false;

  if (atomic_read(&bo->gpu_usecount)) return false;

• if (!mutex_trylock(&shmem->pages_lock))

• if (!mutex_trylock(&bo->mappings.lock)) return false;

• panfrost_gem_teardown_mappings(bo);

• if (!mutex_trylock(&shmem->pages_lock))

• goto unlock_mappings;
  

• panfrost_gem_teardown_mappings_locked(bo); drm_gem_shmem_purge_locked(obj);

• ret = true;

  mutex_unlock(&shmem->pages_lock);

• return true;

+unlock_mappings:

• mutex_unlock(&bo->mappings.lock);

• return ret; }

  static unsigned long