linux-kernel - [PATCH AUTOSEL 6.4 25/40] drm/amdgpu: Fix potential fence use-after-free v2

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Message-Id: <20230724013140.2327815-25-sashal@kernel.org>
Date:   Sun, 23 Jul 2023 21:31:25 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     shanzhulig <shanzhulig@...il.com>,
        Christian König <christian.koenig@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>, airlied@...ux.ie,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 6.4 25/40] drm/amdgpu: Fix potential fence use-after-free v2

From: shanzhulig <shanzhulig@...il.com>

[ Upstream commit 2e54154b9f27262efd0cb4f903cc7d5ad1fe9628 ]

fence Decrements the reference count before exiting.
Avoid Race Vulnerabilities for fence use-after-free.

v2 (chk): actually fix the use after free and not just move it.

Signed-off-by: shanzhulig <shanzhulig@...il.com>
Signed-off-by: Christian König <christian.koenig@....com>
Reviewed-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
index 2eb2c66843a88..71a9c4ab905f6 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
@@ -1624,15 +1624,15 @@ static int amdgpu_cs_wait_all_fences(struct amdgpu_device *adev,
 			continue;
 
 		r = dma_fence_wait_timeout(fence, true, timeout);
+		if (r > 0 && fence->error)
+			r = fence->error;
+
 		dma_fence_put(fence);
 		if (r < 0)
 			return r;
 
 		if (r == 0)
 			break;
-
-		if (fence->error)
-			return fence->error;
 	}
 
 	memset(wait, 0, sizeof(*wait));
-- 
2.39.2