Re: [PATCHv2 2/4] tty: Hold tty_ldisc_lock() during tty_reopen()
On 09/03/2018, 06:52 PM, 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 2260
> 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
> Cc: Jiri Slaby
Reviewed-by: Jiri Slaby
> Cc: sta...@vger.kernel.org # depends on commit b027e2298bd5 ("tty: fix
> data race between tty_init_dev and flush of buf")
> Reported-by: syzbot+3aa9784721dfb90e9...@syzkaller.appspotmail.com
> Tested-by: Tetsuo Handa
> Signed-off-by: Dmitry Safonov
thanks,
--
js
suse labs
Re: [PATCHv2 2/4] tty: Hold tty_ldisc_lock() during tty_reopen()
On 09/03/2018, 06:52 PM, 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 2260
> 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
> Cc: Jiri Slaby
Reviewed-by: Jiri Slaby
> Cc: sta...@vger.kernel.org # depends on commit b027e2298bd5 ("tty: fix
> data race between tty_init_dev and flush of buf")
> Reported-by: syzbot+3aa9784721dfb90e9...@syzkaller.appspotmail.com
> Tested-by: Tetsuo Handa
> Signed-off-by: Dmitry Safonov
thanks,
--
js
suse labs
Re: [PATCHv2 2/4] tty: Hold tty_ldisc_lock() during tty_reopen()
On (09/04/18 08:30), Jiri Slaby wrote:
>
> >> Cc: sta...@vger.kernel.org # 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: sta...@vger.kernel.org
>
> Nope, it would be translated as:
> Backport-first: b027e2298bd5
> :)
:) Ah, OK.
So this "Backport-first:" is for pre-4.9 longterm kernels.
As far as I can see linux-4.9.y picked up b027e2298bd5:
commit 55eaecffe3d663d02084023b9fc06d5f39b97389
Author: Gaurav Kohli
Date: Tue Jan 23 13:16:34 2018 +0530
tty: fix data race between tty_init_dev and flush of buf
commit b027e2298bd588d6fa36ed2eda97447fb3eac078 upstream.
-ss
Re: [PATCHv2 2/4] tty: Hold tty_ldisc_lock() during tty_reopen()
On (09/04/18 08:30), Jiri Slaby wrote:
>
> >> Cc: sta...@vger.kernel.org # 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: sta...@vger.kernel.org
>
> Nope, it would be translated as:
> Backport-first: b027e2298bd5
> :)
:) Ah, OK.
So this "Backport-first:" is for pre-4.9 longterm kernels.
As far as I can see linux-4.9.y picked up b027e2298bd5:
commit 55eaecffe3d663d02084023b9fc06d5f39b97389
Author: Gaurav Kohli
Date: Tue Jan 23 13:16:34 2018 +0530
tty: fix data race between tty_init_dev and flush of buf
commit b027e2298bd588d6fa36ed2eda97447fb3eac078 upstream.
-ss
Re: [PATCHv2 2/4] tty: Hold tty_ldisc_lock() during tty_reopen()
On 09/04/2018, 03:51 AM, Sergey Senozhatsky wrote:
> 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 2260
>> 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
>> Cc: Jiri Slaby
>> Cc: sta...@vger.kernel.org # 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: sta...@vger.kernel.org
Nope, it would be translated as:
Backport-first: b027e2298bd5
:)
thanks,
--
js
suse labs
Re: [PATCHv2 2/4] tty: Hold tty_ldisc_lock() during tty_reopen()
On 09/04/2018, 03:51 AM, Sergey Senozhatsky wrote:
> 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 2260
>> 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
>> Cc: Jiri Slaby
>> Cc: sta...@vger.kernel.org # 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: sta...@vger.kernel.org
Nope, it would be translated as:
Backport-first: b027e2298bd5
:)
thanks,
--
js
suse labs
Re: [PATCHv2 2/4] tty: Hold tty_ldisc_lock() during tty_reopen()
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 2260
> 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
> Cc: Jiri Slaby
> Cc: sta...@vger.kernel.org # 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: sta...@vger.kernel.org
-ss
Re: [PATCHv2 2/4] tty: Hold tty_ldisc_lock() during tty_reopen()
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 2260
> 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
> Cc: Jiri Slaby
> Cc: sta...@vger.kernel.org # 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: sta...@vger.kernel.org
-ss
