Re: [PATCH] tty: ldisc: fix deadlock between ldisc_sem and rtnl_mutex

Hi Jagielski,

On 7/16/26 15:59, Jagielski, Jedrzej wrote:
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> From: Yun Zhou <[email protected]>
> Sent: Thursday, July 16, 2026 8:47 AM
> 
>> syzbot reported a circular lock dependency involving tty ldisc_sem and
>> the networking rtnl_mutex. The full chain is:
>>
>>   rtnl_mutex --> nft_commit_mutex --> ... --> ep->mtx --> ldisc_sem --> rtnl_mutex
> 
> still unclear where the first mutex may come from

   tty_set_ldisc()
     tty_ldisc_lock()        <- hold ldisc_sem
       tty_ldisc_open()
         slcan_open()
           register_candev()
             register_netdev()
               rtnl_net_lock_killable()  <- hold rtnl_mutex

> 
>>
>> +      tty_ldisc_unlock(tty);
>>
>> +      /*
> 
> this blank line is redundant i believe
> 

Isn't it common practice to leave the first line of a multi-line comment 
blank? Does it violate the coding style guidelines?

BR,
Yun