[PATCH AUTOSEL 4.19 25/25] drm/amdgpu: Fix a use-after-free

[Sasha Levin <sashal@kernel.org>]

From: xinhui pan <xinhui.pan@amd.com>

[ Upstream commit 1e5c37385097c35911b0f8a0c67ffd10ee1af9a2 ]

looks like we forget to set ttm->sg to NULL.
Hit panic below

[ 1235.844104] general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b7b4b: 0000 [#1] SMP DEBUG_PAGEALLOC NOPTI
[ 1235.989074] Call Trace:
[ 1235.991751]  sg_free_table+0x17/0x20
[ 1235.995667]  amdgpu_ttm_backend_unbind.cold+0x4d/0xf7 [amdgpu]
[ 1236.002288]  amdgpu_ttm_backend_destroy+0x29/0x130 [amdgpu]
[ 1236.008464]  ttm_tt_destroy+0x1e/0x30 [ttm]
[ 1236.013066]  ttm_bo_cleanup_memtype_use+0x51/0xa0 [ttm]
[ 1236.018783]  ttm_bo_release+0x262/0xa50 [ttm]
[ 1236.023547]  ttm_bo_put+0x82/0xd0 [ttm]
[ 1236.027766]  amdgpu_bo_unref+0x26/0x50 [amdgpu]
[ 1236.032809]  amdgpu_amdkfd_gpuvm_alloc_memory_of_gpu+0x7aa/0xd90 [amdgpu]
[ 1236.040400]  kfd_ioctl_alloc_memory_of_gpu+0xe2/0x330 [amdgpu]
[ 1236.046912]  kfd_ioctl+0x463/0x690 [amdgpu]

Signed-off-by: xinhui pan <xinhui.pan@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index 757fa486aac4..50807d621eca 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -1277,6 +1277,7 @@ static void amdgpu_ttm_tt_unpopulate(struct ttm_tt *ttm)
 	if (gtt && gtt->userptr) {
 		amdgpu_ttm_tt_set_user_pages(ttm, NULL);
 		kfree(ttm->sg);
+		ttm->sg = NULL;
 		ttm->page_flags &= ~TTM_PAGE_FLAG_SG;
 		return;
 	}
-- 
2.30.2