From: Greg KH <gregkh@linuxfoundation.org>
To: Jiri Slaby <jslaby@suse.cz>
Cc: linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org,
syzbot+26183d9746e62da329b8@syzkaller.appspotmail.com
Subject: Re: [PATCH 2/2] vt: selection, push sel_lock up
Date: Fri, 28 Feb 2020 14:04:00 +0100 [thread overview]
Message-ID: <20200228130400.GA3017265@kroah.com> (raw)
In-Reply-To: <71582fee-257c-3ef4-7c03-3d43651898ff@suse.cz>
On Fri, Feb 28, 2020 at 01:59:36PM +0100, Jiri Slaby wrote:
> On 28. 02. 20, 13:03, Greg KH wrote:
> > On Fri, Feb 28, 2020 at 12:54:06PM +0100, Jiri Slaby wrote:
> >> sel_lock cannot nest in the console lock. Thanks to syzkaller, the
> >> kernel states firmly:
> >>
> >>> WARNING: possible circular locking dependency detected
> >>> 5.6.0-rc3-syzkaller #0 Not tainted
> >>> ------------------------------------------------------
> >>> syz-executor.4/20336 is trying to acquire lock:
> >>> ffff8880a2e952a0 (&tty->termios_rwsem){++++}, at: tty_unthrottle+0x22/0x100 drivers/tty/tty_ioctl.c:136
> ...
> >>> other info that might help us debug this:
> >>>
> >>> Chain exists of:
> >>> &tty->termios_rwsem --> console_lock --> sel_lock
> >>
> >> Clearly. From the above, we have:
> >> console_lock -> sel_lock
> >> sel_lock -> termios_rwsem
> >> termios_rwsem -> console_lock
> >>
> >> Fix this by reversing the console_lock -> sel_lock dependency in
> >> ioctl(TIOCL_SETSEL). First, lock sel_lock, then console_lock.
> >>
> >> Signed-off-by: Jiri Slaby <jslaby@suse.cz>
> >> Reported-by: syzbot+26183d9746e62da329b8@syzkaller.appspotmail.com
> >> Fixes: 07e6124a1a46 ("vt: selection, close sel_buffer race")
> >
> > As 07e6124a1a46 was marked for stable, both of these should be as well,
> > right?
>
> Ah, yes. My bad again, sorry.
>
> > And did you happen to test these two with the syzbot tool to see if it
> > really did fix the report?
>
> Nope, this syz* stuff is a black magic for me. How can I do that?
From the syzbot report at the bottom it says:
syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches
Try running these through that and let's see if we get a "success"
report or not.
thanks,
greg k-h
prev parent reply other threads:[~2020-02-28 13:04 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-28 11:54 [PATCH 1/2] vt: selection, push console lock down Jiri Slaby
2020-02-28 11:54 ` [PATCH 2/2] vt: selection, push sel_lock up Jiri Slaby
2020-02-28 12:03 ` Greg KH
2020-02-28 12:59 ` Jiri Slaby
2020-02-28 13:04 ` Greg KH [this message]
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