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Wed, 23 Sep 2026 21:51:35 -0700 (PDT) Received: from Raccoon ([113.30.177.23]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-33e95c7bf6bsm9791270eec.8.2026.09.23.21.51.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Sep 2026 21:51:35 -0700 (PDT) From: Rohinthan P To: mchehab@kernel.org Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+ea047a32630b1f47da67@syzkaller.appspotmail.com Subject: [PATCH] media: as102: initialize bus_adap.lock and sem mutexes before DVB registration Date: Thu, 24 Sep 2026 10:21:28 +0530 Message-ID: <20260924045129.12794-1-rokinthanp03@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit In as102_dvb_register(), mutex_init(&as102_dev->bus_adap.lock) and mutex_init(&as102_dev->sem) are called at the end of the function, after dvb_register_frontend() has already registered the frontend device node to userspace. If userspace opens the frontend node immediately after registration, dvb_frontend_open() invokes fe->ops.ts_bus_ctrl(fe, 1), which calls as102_stream_ctrl(). In as102_stream_ctrl(), bus_adap->lock is acquired via mutex_lock_interruptible(&bus_adap->lock). Because the mutex has not yet been initialized, DEBUG_LOCKS_WARN_ON(lock->magic != lock) is triggered: DEBUG_LOCKS_WARN_ON(lock->magic != lock) WARNING: kernel/locking/mutex.c:625 at __mutex_lock+0x12d8/0x1550 ... Call Trace: as102_stream_ctrl+0x27/0xc0 drivers/media/usb/as102/as102_drv.c:259 dvb_frontend_open+0x7e2/0x1410 drivers/media/dvb-core/dvb_frontend.c:2825 dvb_device_open+0x24f/0x340 drivers/media/dvb-core/dvbdev.c:109 chrdev_open+0x4d9/0x600 fs/char_dev.c:411 Similarly, as102_dev->sem protects starting and stopping feeds via as102_dvb_dmx_start_feed() / as102_dvb_dmx_stop_feed(), and was also initialized after the demux device was initialized and frontend registered. Move mutex_init() for both bus_adap.lock and sem to the beginning of as102_dvb_register(), ensuring that the mutexes are initialized before the adapter, demux, or frontend are exposed to userspace. Fixes: 47f79129ecf5 ("[media] as102: prepare as102_fe to be compiled as a module") Reported-by: syzbot+ea047a32630b1f47da67@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=ea047a32630b1f47da67 Signed-off-by: Rohinthan P --- drivers/media/usb/as102/as102_drv.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/drivers/media/usb/as102/as102_drv.c b/drivers/media/usb/as102/as102_drv.c index 6b1d352..a6dd675 100644 --- a/drivers/media/usb/as102/as102_drv.c +++ b/drivers/media/usb/as102/as102_drv.c @@ -287,6 +287,12 @@ int as102_dvb_register(struct as102_dev_t *as102_dev) struct device *dev = &as102_dev->bus_adap.usb_dev->dev; int ret; + /* init bus mutex for token locking */ + mutex_init(&as102_dev->bus_adap.lock); + + /* init start / stop stream mutex */ + mutex_init(&as102_dev->sem); + ret = dvb_register_adapter(&as102_dev->dvb_adap, as102_dev->name, THIS_MODULE, dev, adapter_nr); @@ -341,12 +347,6 @@ int as102_dvb_register(struct as102_dev_t *as102_dev) goto efereg; } - /* init bus mutex for token locking */ - mutex_init(&as102_dev->bus_adap.lock); - - /* init start / stop stream mutex */ - mutex_init(&as102_dev->sem); - /* * try to load as102 firmware. If firmware upload failed, we'll be * able to upload it later. -- 2.53.0