From: Greg KH <gregkh@linuxfoundation.org>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: syzbot <syzbot+b308f5fd049fbbc6e74f@syzkaller.appspotmail.com>,
linux-fbdev@vger.kernel.org,
George Kennedy <george.kennedy@oracle.com>,
b.zolnierkie@samsung.com, daniel.vetter@ffwll.ch, deller@gmx.de,
syzkaller-bugs@googlegroups.com, linux-kernel@vger.kernel.org,
dri-devel@lists.freedesktop.org,
Linus Torvalds <torvalds@linux-foundation.org>,
jirislaby@kernel.org, Peilin Ye <yepeilin.cs@gmail.com>
Subject: Re: [PATCH] vt_ioctl: make VT_RESIZEX behave like VT_RESIZE
Date: Sun, 27 Sep 2020 14:06:58 +0200 [thread overview]
Message-ID: <20200927120658.GA107433@kroah.com> (raw)
In-Reply-To: <4933b81b-9b1a-355b-df0e-9b31e8280ab9@i-love.sakura.ne.jp>
On Sun, Sep 27, 2020 at 08:46:30PM +0900, Tetsuo Handa wrote:
> syzbot is reporting UAF/OOB read at bit_putcs()/soft_cursor() [1][2], for
> vt_resizex() from ioctl(VT_RESIZEX) allows setting font height larger than
> actual font height calculated by con_font_set() from ioctl(PIO_FONT).
> Since fbcon_set_font() from con_font_set() allocates minimal amount of
> memory based on actual font height calculated by con_font_set(),
> use of vt_resizex() can cause UAF/OOB read for font data.
>
> VT_RESIZEX was introduced in Linux 1.3.3, but it is unclear that what
> comes to the "+ more" part, and I couldn't find a user of VT_RESIZEX.
>
> #define VT_RESIZE 0x5609 /* set kernel's idea of screensize */
> #define VT_RESIZEX 0x560A /* set kernel's idea of screensize + more */
>
> So far we are not aware of syzbot reports caused by setting non-zero value
> to v_vlin parameter. But given that it is possible that nobody is using
> VT_RESIZEX, we can try removing support for v_clin and v_vlin parameters.
Debian code search doesn't show any users, and that's usually a good
indication of what userspace ioctls for old things like this, are being
used for.
So this makes sense to me, I'll queue it up, thanks!
greg k-h
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next prev parent reply other threads:[~2020-09-27 12:06 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-23 17:30 KASAN: use-after-free Read in bit_putcs syzbot
2020-09-26 2:03 ` syzbot
2020-09-26 16:25 ` Tetsuo Handa
2020-09-26 19:39 ` Peilin Ye
2020-09-27 0:25 ` Tetsuo Handa
2020-09-27 8:28 ` Tetsuo Handa
2020-09-27 9:27 ` Peilin Ye
2020-09-27 11:46 ` [PATCH] vt_ioctl: make VT_RESIZEX behave like VT_RESIZE Tetsuo Handa
2020-09-27 12:06 ` Greg KH [this message]
2020-09-28 17:59 ` Martin Hostettler
2020-09-29 1:12 ` Tetsuo Handa
2020-09-29 10:52 ` Martin Hostettler
2020-09-29 16:56 ` Daniel Vetter
2020-09-29 17:10 ` Greg KH
2021-04-11 21:43 ` Maciej W. Rozycki
2021-04-11 22:15 ` Linus Torvalds
2021-04-12 7:01 ` Daniel Vetter
2021-04-12 13:30 ` Maciej W. Rozycki
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