Re: general protection fault in syscall_return_slowpath

[Dan Carpenter]

On Sun, Mar 08, 2020 at 09:29:04AM -0700, Andy Lutomirski wrote:
> On Sat, Mar 7, 2020 at 11:45 PM syzbot
> <syzbot+cd66e43794b178bb5cd6@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> >
> > Hello,
> >
> > syzbot found the following crash on:
> >
> > HEAD commit:    63623fd4 Merge tag 'for-linus' of git://git.kernel.org/pub..
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=16cfeac3e00000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=5d2e033af114153f
> > dashboard link: https://syzkaller.appspot.com/bug?extid=cd66e43794b178bb5cd6
> > compiler:       clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12a42329e00000
> >
> 
> I bet this is due to entirely missing input validation in
> con_font_copy() and/or fbcon_copy_font().

The only thing we use in con_font_copy() is op->height and we clamp it
to 0-MAX_NR_CONSOLES (64).

regards,
dan carpenter