[PATCH v2] drm/amdgpu: unmap GART dma pages before free

[Michail Tatas <michail.tatas@gmail.com>]

amdgpu_gart_table_ram_alloc() maps the GART dma pages
and neither the error path nor amdgpu_gart_table_ram_free()
unmaps those pages before freeing them, which could leave
the device writing to freed memory.

Fix by unmapping the GART dma pages before freeing them.

Signed-off-by: Michail Tatas <michail.tatas@gmail.com>
---

Changes in v2:
- Fixed a null dereference possibility based on review 
  from sashiko

Revisions:
- v1: https://lore.kernel.org/all/arKhDFCSoPDNYaxX@michalis-linux/

 drivers/gpu/drm/amd/amdgpu/amdgpu_gart.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gart.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gart.c
index c4c21dbbbdbf..116c646b86a8 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gart.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gart.c
@@ -209,6 +209,8 @@ int amdgpu_gart_table_ram_alloc(struct amdgpu_device *adev)
 error_resv:
 	amdgpu_bo_unreserve(bo);
 error:
+	dma_unmap_page(&adev->pdev->dev, dma_addr, adev->gart.table_size,
+		       DMA_BIDIRECTIONAL);
 	amdgpu_bo_unref(&bo);
 	if (sg) {
 		sg_free_table(sg);
@@ -240,6 +242,8 @@ void amdgpu_gart_table_ram_free(struct amdgpu_device *adev)
 		amdgpu_bo_unreserve(adev->gart.bo);
 	}
 	amdgpu_bo_unref(&adev->gart.bo);
+	dma_unmap_page(&adev->pdev->dev, sg_dma_address(sg->sgl), adev->gart.table_size,
+		       DMA_BIDIRECTIONAL);
 	sg_free_table(sg);
 	kfree(sg);
 	p = virt_to_page(adev->gart.ptr);
-- 
2.43.0