linux-kernel - [PATCH 5.4 082/340] media: imx: Fix csc/scaler unregister

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Message-Id: <20210301161052.361891265@linuxfoundation.org>
Date:   Mon,  1 Mar 2021 17:10:26 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ezequiel Garcia <ezequiel@...labora.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 082/340] media: imx: Fix csc/scaler unregister

From: Ezequiel Garcia <ezequiel@...labora.com>

[ Upstream commit 89b14485caa4b7b2eaf70be0064f0978e68ebeee ]

The csc/scaler device private struct is released by
ipu_csc_scaler_video_device_release(), which can be called
by video_unregister_device() if there are no users
of the underlying struct video device.

Therefore, the mutex can't be held when calling
video_unregister_device() as its memory may be freed
by it, leading to a kernel oops.

Fortunately, the fix is quite simple as no locking
is needed when calling video_unregister_device(): v4l2-core
already has its own internal locking, and the structures
are also properly refcounted.

Fixes: a8ef0488cc59 ("media: imx: add csc/scaler mem2mem device")
Signed-off-by: Ezequiel Garcia <ezequiel@...labora.com>
Reviewed-by: Philipp Zabel <p.zabel@...gutronix.de>
Signed-off-by: Hans Verkuil <hverkuil-cisco@...all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/staging/media/imx/imx-media-csc-scaler.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/drivers/staging/media/imx/imx-media-csc-scaler.c b/drivers/staging/media/imx/imx-media-csc-scaler.c
index 2b635ebf62d6a..a15d970adb983 100644
--- a/drivers/staging/media/imx/imx-media-csc-scaler.c
+++ b/drivers/staging/media/imx/imx-media-csc-scaler.c
@@ -866,11 +866,7 @@ void imx_media_csc_scaler_device_unregister(struct imx_media_video_dev *vdev)
 	struct ipu_csc_scaler_priv *priv = vdev_to_priv(vdev);
 	struct video_device *vfd = priv->vdev.vfd;
 
-	mutex_lock(&priv->mutex);
-
 	video_unregister_device(vfd);
-
-	mutex_unlock(&priv->mutex);
 }
 
 struct imx_media_video_dev *
-- 
2.27.0