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 _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
