Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Dmitry Osipenko <dmitry.osipenko@collabora.com>
To:     Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Sumit Semwal <sumit.semwal@linaro.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        =?UTF-8?q?Christian=20K=C3=B6nig?= <christian.koenig@amd.com>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>, noralf@tronnes.org,
        Dan Carpenter <dan.carpenter@oracle.com>
Cc:     dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org
Subject: [PATCH v2 1/2] dma-buf: Make locking consistent in dma_buf_detach()
Date:   Sun, 30 Oct 2022 18:44:11 +0300
Message-Id: <20221030154412.8320-2-dmitry.osipenko@collabora.com>
In-Reply-To: <20221030154412.8320-1-dmitry.osipenko@collabora.com>
References: <20221030154412.8320-1-dmitry.osipenko@collabora.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Precedence: bulk

The dma_buf_detach() locks attach->dmabuf->resv and then unlocks
dmabuf->resv, which could be a two different locks from a static
code checker perspective. In particular this triggers Smatch to
report the "double unlock" error. Make the locking pointers consistent.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://lore.kernel.org/dri-devel/Y1fLfsccW3AS%2Fo+%2F@kili/
Fixes: 809d9c72c2f8 ("dma-buf: Move dma_buf_attach() to dynamic locking specification")
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 drivers/dma-buf/dma-buf.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index c40d72d318fd..13bfd2d09c56 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -995,10 +995,10 @@ static void __unmap_dma_buf(struct dma_buf_attachment *attach,
  */
 void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
 {
-	if (WARN_ON(!dmabuf || !attach))
+	if (WARN_ON(!dmabuf || !attach || dmabuf != attach->dmabuf))
 		return;
 
-	dma_resv_lock(attach->dmabuf->resv, NULL);
+	dma_resv_lock(dmabuf->resv, NULL);
 
 	if (attach->sgt) {
 
-- 
2.37.3