Re: [PATCH v3] media: dvb-core: fix use-after-free in dvb_frontend_open()

["Zhou, Yun" <yun.zhou@windriver.com>]

Friendly ping again

On 6/25/26 19:24, Zhou, Yun wrote:
> Friendly ping
> 
> On 6/10/26 16:30, Yun Zhou wrote:
>> dvb_frontend_open() calls dvb_generic_release() in its error path after
>> dvb_generic_open() succeeds. dvb_generic_release() drops the device
>> reference via dvb_device_put(), and then dvb_device_open() drops it again
>> in its error handling, causing a use-after-free and refcount underflow.
>>
>> Fix this by incrementing the refcount before dvb_generic_release() in the
>> error path, so that the put inside dvb_generic_release() is balanced and
>> dvb_device_open() remains the sole effective put on open failure.
>>
>> Reported-by: syzbot+40339ea82afa8184ad5d@syzkaller.appspotmail.com
>> Closes: https://syzkaller.appspot.com/bug?extid=40339ea82afa8184ad5d
>> Cc: stable@vger.kernel.org
>> Fixes: 0fc044b2b5e2 ("media: dvbdev: adopts refcnt to avoid UAF")
>> Signed-off-by: Yun Zhou <yun.zhou@windriver.com>
>> ---
>> v3:
>>   - Simplify fix: increment refcount before dvb_generic_release() instead
>>     of introducing __dvb_generic_release()
>>
>> v2:
>>   - Fix Fixes tag commit title
>>   - Add Closes: link after Reported-by
>>   - Cc stable@vger.kernel.org
>>
>>   drivers/media/dvb-core/dvb_frontend.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/media/dvb-core/dvb_frontend.c b/drivers/media/ 
>> dvb-core/dvb_frontend.c
>> index d082b6c57c76..608525d08277 100644
>> --- a/drivers/media/dvb-core/dvb_frontend.c
>> +++ b/drivers/media/dvb-core/dvb_frontend.c
>> @@ -2887,6 +2887,7 @@ static int dvb_frontend_open(struct inode 
>> *inode, struct file *file)
>>       mutex_unlock(&fe->dvb->mdev_lock);
>>   err2:
>>   #endif
>> +    dvb_device_get(dvbdev);
>>       dvb_generic_release(inode, file);
>>   err1:
>>       if (dvbdev->users == -1 && fe->ops.ts_bus_ctrl)
>