Re: [PATCHv2 2/4] tty: Hold tty_ldisc_lock() during tty_reopen()

[Sergey Senozhatsky]

On (09/03/18 17:52), Dmitry Safonov wrote:
> 
> 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
> 
> tty_ldisc_reinit() should be called with ldisc_sem hold for writing,
> which will protect any reader against line discipline changes.
> 
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: Jiri Slaby <jslaby@xxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx # depends on commit b027e2298bd5 ("tty: fix
> data race between tty_init_dev and flush of buf")

I believe there's a "Fixes" tag for that

Fixes: b027e2298bd5 ("tty: fix data race between tty_init_dev and flush of buf")
Cc: stable@xxxxxxxxxxxxxxx

	-ss