lkml.org 
[lkml]   [2020]   [Sep]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] vt_ioctl: make VT_RESIZEX behave like VT_RESIZE
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

\
 
 \ /
  Last update: 2020-09-27 14:07    [W:0.094 / U:0.100 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site