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From:   Pavel Skripkin <paskripkin@gmail.com>
To:     mkrufky@linuxtv.org, mchehab@kernel.org, crope@iki.fi
Cc:     linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
        Pavel Skripkin <paskripkin@gmail.com>,
        syzbot+5ca0bf339f13c4243001@syzkaller.appspotmail.com
Subject: [PATCH] media: mxl111sf: change mutex_init() location
Date:   Sat, 31 Jul 2021 00:38:29 +0300
Message-Id: <20210730213829.2909-1-paskripkin@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Syzbot reported, that mxl111sf_ctrl_msg() uses uninitialized
mutex. The problem was in wrong mutex_init() location.

Previous mutex_init(&state->msg_lock) call was in ->init() function, but
dvb_usbv2_init() has this order of calls:

	dvb_usbv2_init()
	  dvb_usbv2_adapter_init()
	    dvb_usbv2_adapter_frontend_init()
	      props->frontend_attach()

	  props->init()

Since mxl111sf_frontend_attach_atsc_mh() calls mxl111sf_ctrl_msg()
internally we need to initialize state->msg_lock in it to make lockdep
happy.

Reported-and-tested-by: syzbot+5ca0bf339f13c4243001@syzkaller.appspotmail.com
Fixes: 8572211842af ("[media] mxl111sf: convert to new DVB USB")
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
---
 drivers/media/usb/dvb-usb-v2/mxl111sf.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/media/usb/dvb-usb-v2/mxl111sf.c b/drivers/media/usb/dvb-usb-v2/mxl111sf.c
index 7865fa0a8295..2e5663ffa7ce 100644
--- a/drivers/media/usb/dvb-usb-v2/mxl111sf.c
+++ b/drivers/media/usb/dvb-usb-v2/mxl111sf.c
@@ -931,8 +931,6 @@ static int mxl111sf_init(struct dvb_usb_device *d)
 		  .len = sizeof(eeprom), .buf = eeprom },
 	};
 
-	mutex_init(&state->msg_lock);
-
 	ret = get_chip_info(state);
 	if (mxl_fail(ret))
 		pr_err("failed to get chip info during probe");
@@ -979,8 +977,12 @@ static int mxl111sf_frontend_attach_mh(struct dvb_usb_adapter *adap)
 static int mxl111sf_frontend_attach_atsc_mh(struct dvb_usb_adapter *adap)
 {
 	int ret;
+	struct mxl111sf_state *state = d_to_priv(adap_to_d(adap));
+
 	pr_debug("%s\n", __func__);
 
+	mutex_init(&state->msg_lock);
+
 	ret = mxl111sf_lgdt3305_frontend_attach(adap, 0);
 	if (ret < 0)
 		return ret;
-- 
2.32.0