linux-fbdev.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
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 12:06:58 +0000	[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

  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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200927120658.GA107433@kroah.com \
    --to=gregkh@linuxfoundation.org \
    --cc=b.zolnierkie@samsung.com \
    --cc=daniel.vetter@ffwll.ch \
    --cc=deller@gmx.de \
    --cc=dri-devel@lists.freedesktop.org \
    --cc=george.kennedy@oracle.com \
    --cc=jirislaby@kernel.org \
    --cc=linux-fbdev@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=penguin-kernel@i-love.sakura.ne.jp \
    --cc=syzbot+b308f5fd049fbbc6e74f@syzkaller.appspotmail.com \
    --cc=syzkaller-bugs@googlegroups.com \
    --cc=torvalds@linux-foundation.org \
    --cc=yepeilin.cs@gmail.com \
    --subject='Re: [PATCH] vt_ioctl: make VT_RESIZEX behave like VT_RESIZE' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).