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authorBoris Brezillon <boris.brezillon@collabora.com>2019-11-29 14:59:04 +0100
committerRob Herring <robh@kernel.org>2019-12-06 11:06:16 -0600
commitaed44cbeae2b7674cd155ba5cc6506aafe46a94e (patch)
treeca806245e28d14a4f018ef7fd675d4216bfffddf
parent3bb69dbcb9e8430e0cc9990cff427ca3ae25ffdc (diff)
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: 013b65101315 ("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
-rw-r--r--drivers/gpu/drm/panfrost/panfrost_gem.c15
1 files changed, 10 insertions, 5 deletions
diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.c b/drivers/gpu/drm/panfrost/panfrost_gem.c
index deca0c30bbd4..fa1b2732a3a8 100644
--- a/drivers/gpu/drm/panfrost/panfrost_gem.c
+++ b/drivers/gpu/drm/panfrost/panfrost_gem.c
@@ -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);
}