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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Guchun Chen <guchun.chen@amd.com>,
        =?UTF-8?q?Christian=20K=C3=B6nig?= <christian.koenig@amd.com>,
        Alex Deucher <alexander.deucher@amd.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.12 251/384] drm/amdgpu: fix NULL pointer dereference
Date:   Mon, 10 May 2021 12:20:40 +0200
Message-Id: <20210510102023.158865963@linuxfoundation.org>
In-Reply-To: <20210510102014.849075526@linuxfoundation.org>
References: <20210510102014.849075526@linuxfoundation.org>
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From: Guchun Chen <guchun.chen@amd.com>

[ Upstream commit 3c3dc654333f6389803cdcaf03912e94173ae510 ]

ttm->sg needs to be checked before accessing its child member.

Call Trace:
 amdgpu_ttm_backend_destroy+0x12/0x70 [amdgpu]
 ttm_bo_cleanup_memtype_use+0x3a/0x60 [ttm]
 ttm_bo_release+0x17d/0x300 [ttm]
 amdgpu_bo_unref+0x1a/0x30 [amdgpu]
 amdgpu_amdkfd_gpuvm_alloc_memory_of_gpu+0x78b/0x8b0 [amdgpu]
 kfd_ioctl_alloc_memory_of_gpu+0x118/0x220 [amdgpu]
 kfd_ioctl+0x222/0x400 [amdgpu]
 ? kfd_dev_is_large_bar+0x90/0x90 [amdgpu]
 __x64_sys_ioctl+0x8e/0xd0
 ? __context_tracking_exit+0x52/0x90
 do_syscall_64+0x33/0x80
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f97f264d317
Code: b3 66 90 48 8b 05 71 4b 2d 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 41 4b 2d 00 f7 d8 64 89 01 48
RSP: 002b:00007ffdb402c338 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f97f3cc63a0 RCX: 00007f97f264d317
RDX: 00007ffdb402c380 RSI: 00000000c0284b16 RDI: 0000000000000003
RBP: 00007ffdb402c380 R08: 00007ffdb402c428 R09: 00000000c4000004
R10: 00000000c4000004 R11: 0000000000000246 R12: 00000000c0284b16
R13: 0000000000000003 R14: 00007f97f3cc63a0 R15: 00007f8836200000

Signed-off-by: Guchun Chen <guchun.chen@amd.com>
Acked-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 | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index f61fd2cf3fee..383c178cf074 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -942,7 +942,7 @@ static void amdgpu_ttm_tt_unpin_userptr(struct ttm_bo_device *bdev,
 		DMA_BIDIRECTIONAL : DMA_TO_DEVICE;
 
 	/* double check that we don't free the table twice */
-	if (!ttm->sg->sgl)
+	if (!ttm->sg || !ttm->sg->sgl)
 		return;
 
 	/* unmap the pages mapped to the device */
-- 
2.30.2