lkml.org 
[lkml]   [2018]   [Aug]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 2/4] tty: Hold tty_ldisc_lock() during tty_reopen()
From
Date
On 2018/08/29 11:23, Dmitry Safonov wrote:
> tty_ldisc_reinit() doesn't race with neither tty_ldisc_hangup()
> nor set_ldisc() nor tty_ldisc_release() as they use tty lock.
> But it races with anyone who expects line discipline to be the same
> after hoding read semaphore in tty_ldisc_ref().
>
> We've seen the following crash on v4.9.108 stable:
>
> BUG: unable to handle kernel paging request at 0000000000002260
> IP: [..] n_tty_receive_buf_common+0x5f/0x86d
> Workqueue: events_unbound flush_to_ldisc
> Call Trace:
> [..] n_tty_receive_buf2
> [..] tty_ldisc_receive_buf
> [..] flush_to_ldisc
> [..] process_one_work
> [..] worker_thread
> [..] kthread
> [..] ret_from_fork
>
> I think, tty_ldisc_reinit() should be called with ldisc_sem hold for
> writing, which will protect any reader against line discipline changes.
>
> Note: I failed to reproduce the described crash, so obiviously can't
> guarantee that this is the place where line discipline was switched.

This will be same with a report at
https://syzkaller.appspot.com/bug?id=f08670354701fa64cc0dd3c0128a491bdb16adcc .

syzbot is now testing a patch from Jiri Slaby.

\
 
 \ /
  Last update: 2018-08-29 17:19    [W:2.119 / U:0.400 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site