linux-kernel - [PATCH] drm/i915/selftests: fix potential refcnt issue of a dma

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Date:   Thu, 23 Dec 2021 11:39:49 +0800
From:   Xin Xiong <xiongx18@...an.edu.cn>
To:     Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        linaro-mm-sig@...ts.linaro.org
Cc:     yuanxzhang@...an.edu.cn, Xin Xiong <xiongx18@...an.edu.cn>,
        Xiyu Yang <xiyuyang19@...an.edu.cn>,
        Xin Tan <tanxin.ctf@...il.com>
Subject: [PATCH] drm/i915/selftests: fix potential refcnt issue of a dma_buf object

This issue happens in an error path of igt_dmabuf_export_vmap(). When
dma_buf_vmap() succeeds and memchr_inv() returns nonzero, the function
forgets to decrement `vmapping_counter` of the dma_buf object, which
may result in refcount leaks.

Fix it by calling dma_buf_vunmap() under label `out_dma_map` in
certain error path.

Signed-off-by: Xin Xiong <xiongx18@...an.edu.cn>
Signed-off-by: Xiyu Yang <xiyuyang19@...an.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@...il.com>
---
 drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c
index 4a6bb64c3..b24bc506f 100644
--- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c
+++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c
@@ -428,12 +428,14 @@ static int igt_dmabuf_export_vmap(void *arg)
 	if (memchr_inv(ptr, 0, dmabuf->size)) {
 		pr_err("Exported object not initialiased to zero!\n");
 		err = -EINVAL;
-		goto out;
+		goto out_dma_map;
 	}
 
 	memset(ptr, 0xc5, dmabuf->size);
 
 	err = 0;
+
+out_dma_map:
 	dma_buf_vunmap(dmabuf, &map);
 out:
 	dma_buf_put(dmabuf);
-- 
2.25.1