[PATCH 5.15 005/201] drm/ttm: fix locking in vmap/vunmap TTM GEM helpers

[Greg Kroah-Hartman]

From: Christian König <christian.koenig@xxxxxxx>

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@xxxxxxx>
Fixes: 43676605f890 ("drm/ttm: Add vmap/vunmap to TTM and TTM GEM helpers")
Cc: stable@xxxxxxxxxxxxxxx
Reviewed-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20220715111533.467012-1-christian.koenig@xxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/drm_gem_ttm_helper.c |    9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

--- 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_obje
 		     struct dma_buf_map *map)
 {
 	struct ttm_buffer_object *bo = drm_gem_ttm_of_gem(gem);
+	int ret;
 
-	return ttm_bo_vmap(bo, map);
+	dma_resv_lock(gem->resv, NULL);
+	ret = ttm_bo_vmap(bo, map);
+	dma_resv_unlock(gem->resv);
+
+	return ret;
 }
 EXPORT_SYMBOL(drm_gem_ttm_vmap);
 
@@ -82,7 +87,9 @@ void drm_gem_ttm_vunmap(struct drm_gem_o
 {
 	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);