drm/ttm: fix locking in vmap/vunmap TTM GEM helpers

commit dbd0da2453c694f2f74651834d90fb280b57f151 upstream.

I've stumbled over this while reviewing patches for DMA-buf and it looks
like we completely messed the locking up here.

In general most TTM function should only be called while holding the
appropriate BO resv lock. Without this we could break the internal
buffer object state here.

Only compile tested!

Signed-off-by: Christian König <christian.koenig@amd.com>
Fixes: 43676605f890 ("drm/ttm: Add vmap/vunmap to TTM and TTM GEM helpers")
Cc: stable@vger.kernel.org
Reviewed-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220715111533.467012-1-christian.koenig@amd.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/drm_gem_ttm_helper.c b/drivers/gpu/drm/drm_gem_ttm_helper.c
index ecf3d2a..759c65b 100644 (file)
--- a/drivers/gpu/drm/drm_gem_ttm_helper.c
+++ b/drivers/gpu/drm/drm_gem_ttm_helper.c
@@ -64,8 +64,13 @@ int drm_gem_ttm_vmap(struct drm_gem_object *gem,
                     struct dma_buf_map *map)
 {
        struct ttm_buffer_object *bo = drm_gem_ttm_of_gem(gem);
+       int ret;
+
+       dma_resv_lock(gem->resv, NULL);
+       ret = ttm_bo_vmap(bo, map);
+       dma_resv_unlock(gem->resv);
 
-       return ttm_bo_vmap(bo, map);
+       return ret;
 }
 EXPORT_SYMBOL(drm_gem_ttm_vmap);
 
@@ -82,7 +87,9 @@ void drm_gem_ttm_vunmap(struct drm_gem_object *gem,
 {
        struct ttm_buffer_object *bo = drm_gem_ttm_of_gem(gem);
 
+       dma_resv_lock(gem->resv, NULL);
        ttm_bo_vunmap(bo, map);
+       dma_resv_unlock(gem->resv);
 }
 EXPORT_SYMBOL(drm_gem_ttm_vunmap);