[PATCH] drm/amdgpu: Fix a potential sdma invalid access

[Qu Huang]

Before dma_resv_lock(bo->base.resv, NULL) in amdgpu_bo_release_notify(),
the bo->base.resv lock may be held by ttm_mem_evict_first(),
and the VRAM mem will be evicted, mem region was replaced
by Gtt mem region. amdgpu_bo_release_notify() will then
hold the bo->base.resv lock, and SDMA will get an invalid
address in amdgpu_fill_buffer(), resulting in a VMFAULT
or memory corruption.

To avoid it, we have to hold bo->base.resv lock first, and
check whether the mem.mem_type is TTM_PL_VRAM.

Signed-off-by: Qu Huang <jinsdb at 126.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_object.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
index 4b29b82..8018574 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
@@ -1300,12 +1300,16 @@ void amdgpu_bo_release_notify(struct ttm_buffer_object *bo)
 	if (bo->base.resv == &bo->base._resv)
 		amdgpu_amdkfd_remove_fence_on_pt_pd_bos(abo);

-	if (bo->mem.mem_type != TTM_PL_VRAM || !bo->mem.mm_node ||
-	    !(abo->flags & AMDGPU_GEM_CREATE_VRAM_WIPE_ON_RELEASE))
+	if (!(abo->flags & AMDGPU_GEM_CREATE_VRAM_WIPE_ON_RELEASE))
 		return;

 	dma_resv_lock(bo->base.resv, NULL);

+	if (bo->mem.mem_type != TTM_PL_VRAM || !bo->mem.mm_node) {
+		dma_resv_unlock(bo->base.resv);
+		return;
+	}
+
 	r = amdgpu_fill_buffer(abo, AMDGPU_POISON, bo->base.resv, &fence);
 	if (!WARN_ON(r)) {
 		amdgpu_bo_fence(abo, fence, false);
--
1.8.3.1