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From:   Sukrut Bellary <sukrut.bellary@linux.com>
To:     Jeffrey Hugo <quic_jhugo@quicinc.com>,
        Oded Gabbay <ogabbay@kernel.org>,
        Sumit Semwal <sumit.semwal@linaro.org>,
        =?UTF-8?q?Christian=20K=C3=B6nig?= <christian.koenig@amd.com>
Cc:     Sukrut Bellary <sukrut.bellary@linux.com>,
        linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org,
        linaro-mm-sig@lists.linaro.org, linux-media@vger.kernel.org,
        linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org
Subject: [PATCH] accel/qaic: Fix dereferencing freed memory
Date:   Fri,  9 Jun 2023 19:12:00 -0700
Message-Id: <20230610021200.377452-1-sukrut.bellary@linux.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

smatch warning:
	drivers/accel/qaic/qaic_data.c:620 qaic_free_object() error:
		dereferencing freed memory 'obj->import_attach'

obj->import_attach is detached and freed using dma_buf_detach().
But used after free to decrease the dmabuf ref count using
dma_buf_put().

Fixes: ff13be830333 ("accel/qaic: Add datapath")
Signed-off-by: Sukrut Bellary <sukrut.bellary@linux.com>
---
 drivers/accel/qaic/qaic_data.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/accel/qaic/qaic_data.c b/drivers/accel/qaic/qaic_data.c
index e42c1f9ffff8..7cba4d680ea8 100644
--- a/drivers/accel/qaic/qaic_data.c
+++ b/drivers/accel/qaic/qaic_data.c
@@ -613,11 +613,13 @@ static int qaic_gem_object_mmap(struct drm_gem_object *obj, struct vm_area_struc
 static void qaic_free_object(struct drm_gem_object *obj)
 {
 	struct qaic_bo *bo = to_qaic_bo(obj);
+	struct dma_buf *dmabuf;
 
 	if (obj->import_attach) {
 		/* DMABUF/PRIME Path */
+		dmabuf = obj->import_attach->dmabuf;
 		dma_buf_detach(obj->import_attach->dmabuf, obj->import_attach);
-		dma_buf_put(obj->import_attach->dmabuf);
+		dma_buf_put(dmabuf);
 	} else {
 		/* Private buffer allocation path */
 		qaic_free_sgt(bo->sgt);
-- 
2.34.1