From: Greg KH <gregkh@linuxfoundation.org>
To: Jiri Slaby <jslaby@suse.cz>
Cc: linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org,
syzbot+59997e8d5cbdc486e6f6@syzkaller.appspotmail.com
Subject: Re: [PATCH 2/2] vt: selection, close sel_buffer race
Date: Wed, 12 Feb 2020 11:59:09 -0800 [thread overview]
Message-ID: <20200212195909.GA2081344@kroah.com> (raw)
In-Reply-To: <20200210081131.23572-2-jslaby@suse.cz>
On Mon, Feb 10, 2020 at 09:11:31AM +0100, Jiri Slaby wrote:
> syzkaller reported this UAF:
> BUG: KASAN: use-after-free in n_tty_receive_buf_common+0x2481/0x2940 drivers/tty/n_tty.c:1741
> Read of size 1 at addr ffff8880089e40e9 by task syz-executor.1/13184
>
> CPU: 0 PID: 13184 Comm: syz-executor.1 Not tainted 5.4.7 #1
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
> Call Trace:
> ...
> kasan_report+0xe/0x20 mm/kasan/common.c:634
> n_tty_receive_buf_common+0x2481/0x2940 drivers/tty/n_tty.c:1741
> tty_ldisc_receive_buf+0xac/0x190 drivers/tty/tty_buffer.c:461
> paste_selection+0x297/0x400 drivers/tty/vt/selection.c:372
> tioclinux+0x20d/0x4e0 drivers/tty/vt/vt.c:3044
> vt_ioctl+0x1bcf/0x28d0 drivers/tty/vt/vt_ioctl.c:364
> tty_ioctl+0x525/0x15a0 drivers/tty/tty_io.c:2657
> vfs_ioctl fs/ioctl.c:47 [inline]
>
> It is due to a race between parallel paste_selection (TIOCL_PASTESEL)
> and set_selection_user (TIOCL_SETSEL) invocations. One uses sel_buffer,
> while the other frees it and reallocates a new one for another
> selection. Add a mutex to close this race.
>
> The mutex takes care properly of sel_buffer and sel_buffer_lth only. The
> other selection global variables (like sel_start, sel_end, and sel_cons)
> are protected only in set_selection_user. The other functions need quite
> some more work to close the races of the variables there. This is going
> to happen later.
>
> This likely fixes (I am unsure as there is no reproducer provided) bug
> 206361 too. It was marked as CVE-2020-8648.
>
> Signed-off-by: Jiri Slaby <jslaby@suse.cz>
> Reported-by: syzbot+59997e8d5cbdc486e6f6@syzkaller.appspotmail.com
> References: https://bugzilla.kernel.org/show_bug.cgi?id=206361
This needs patch 1 in order to work properly, right?
thanks,
greg k-h
next prev parent reply other threads:[~2020-02-12 19:59 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-10 8:11 [PATCH 1/2] vt: selection, handle pending signals in paste_selection Jiri Slaby
2020-02-10 8:11 ` [PATCH 2/2] vt: selection, close sel_buffer race Jiri Slaby
2020-02-12 19:59 ` Greg KH [this message]
2020-02-13 7:09 ` Jiri Slaby
2020-02-13 19:58 ` Greg KH
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