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From:   Qu Huang <jinsdb@126.com>
To:     alexander.deucher@amd.com, christian.koenig@amd.com,
        airlied@linux.ie, daniel@ffwll.ch, sumit.semwal@linaro.org,
        airlied@redhat.com, ray.huang@amd.com, Mihir.Patel@amd.com,
        nirmoy.aiemd@gmail.com
Cc:     amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
        linux-kernel@vger.kernel.org, linux-media@vger.kernel.org,
        linaro-mm-sig@lists.linaro.org, jinsdb@126.com
Subject: [PATCH] drm/amdgpu: Fix a potential sdma invalid access
Date:   Fri,  2 Apr 2021 11:18:47 +0800
Message-Id: <1617333527-89782-1-git-send-email-jinsdb@126.com>
Precedence: bulk

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@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