--- /dev/null
+From de62c1827d8541d001444fcda74aa0d7d311e6c5 Mon Sep 17 00:00:00 2001
+From: Sasha Levin <sashal@kernel.org>
+Date: Tue, 15 Sep 2020 17:07:35 -0400
+Subject: drm/amdgpu: prevent double kfree ttm->sg
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+From: Philip Yang <Philip.Yang@amd.com>
+
+[ Upstream commit 1d0e16ac1a9e800598dcfa5b6bc53b704a103390 ]
+
+Set ttm->sg to NULL after kfree, to avoid memory corruption backtrace:
+
+[ 420.932812] kernel BUG at
+/build/linux-do9eLF/linux-4.15.0/mm/slub.c:295!
+[ 420.934182] invalid opcode: 0000 [#1] SMP NOPTI
+[ 420.935445] Modules linked in: xt_conntrack ipt_MASQUERADE
+[ 420.951332] Hardware name: Dell Inc. PowerEdge R7525/0PYVT1, BIOS
+1.5.4 07/09/2020
+[ 420.952887] RIP: 0010:__slab_free+0x180/0x2d0
+[ 420.954419] RSP: 0018:ffffbe426291fa60 EFLAGS: 00010246
+[ 420.955963] RAX: ffff9e29263e9c30 RBX: ffff9e29263e9c30 RCX:
+000000018100004b
+[ 420.957512] RDX: ffff9e29263e9c30 RSI: fffff3d33e98fa40 RDI:
+ffff9e297e407a80
+[ 420.959055] RBP: ffffbe426291fb00 R08: 0000000000000001 R09:
+ffffffffc0d39ade
+[ 420.960587] R10: ffffbe426291fb20 R11: ffff9e49ffdd4000 R12:
+ffff9e297e407a80
+[ 420.962105] R13: fffff3d33e98fa40 R14: ffff9e29263e9c30 R15:
+ffff9e2954464fd8
+[ 420.963611] FS: 00007fa2ea097780(0000) GS:ffff9e297e840000(0000)
+knlGS:0000000000000000
+[ 420.965144] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
+[ 420.966663] CR2: 00007f16bfffefb8 CR3: 0000001ff0c62000 CR4:
+0000000000340ee0
+[ 420.968193] Call Trace:
+[ 420.969703] ? __page_cache_release+0x3c/0x220
+[ 420.971294] ? amdgpu_ttm_tt_unpopulate+0x5e/0x80 [amdgpu]
+[ 420.972789] kfree+0x168/0x180
+[ 420.974353] ? amdgpu_ttm_tt_set_user_pages+0x64/0xc0 [amdgpu]
+[ 420.975850] ? kfree+0x168/0x180
+[ 420.977403] amdgpu_ttm_tt_unpopulate+0x5e/0x80 [amdgpu]
+[ 420.978888] ttm_tt_unpopulate.part.10+0x53/0x60 [amdttm]
+[ 420.980357] ttm_tt_destroy.part.11+0x4f/0x60 [amdttm]
+[ 420.981814] ttm_tt_destroy+0x13/0x20 [amdttm]
+[ 420.983273] ttm_bo_cleanup_memtype_use+0x36/0x80 [amdttm]
+[ 420.984725] ttm_bo_release+0x1c9/0x360 [amdttm]
+[ 420.986167] amdttm_bo_put+0x24/0x30 [amdttm]
+[ 420.987663] amdgpu_bo_unref+0x1e/0x30 [amdgpu]
+[ 420.989165] amdgpu_amdkfd_gpuvm_alloc_memory_of_gpu+0x9ca/0xb10
+[amdgpu]
+[ 420.990666] kfd_ioctl_alloc_memory_of_gpu+0xef/0x2c0 [amdgpu]
+
+Signed-off-by: Philip Yang <Philip.Yang@amd.com>
+Reviewed-by: Felix Kuehling <Felix.Kuehling@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 bc746131987ff..ae700e445fbc8 100644
+--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
++++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+@@ -727,6 +727,7 @@ static int amdgpu_ttm_tt_pin_userptr(struct ttm_tt *ttm)
+
+ release_sg:
+ kfree(ttm->sg);
++ ttm->sg = NULL;
+ return r;
+ }
+
+--
+2.25.1
+