Re: Syzkaller found a bug: KASAN: use-after-free Read in do_update_region

[gregkh@xxxxxxxxxxxxxxxxxxx]

On Wed, Nov 23, 2022 at 06:38:01PM +0000, Sanan Hasanov wrote:
> Good day, dear maintainers,
> 
> We found a bug using a modified kernel configuration file used by syzbot.
> 
> We enhanced the coverage of the configuration file using our tool, klocalizer.
> 
> Kernel branch: linux-next 5.11.0-rc1+ (HEAD detached at 6a4b1f2dff55)
> 
> configuration file: https://drive.google.com/file/d/18W-8umgZVSm-KwvIzcBQpxRn74Q1S_Fa/view?usp=sharing
> 
> Unfortunately, we have no reproducer for this bug yet.

Reproducer would be great, thanks.  Otherwise this goes on the thousands
of other "syzbot-found-bugs-with-no-way-to-reproduce" pile that we
have...

> ==================================================================
> BUG: KASAN: use-after-free in do_update_region+0x571/0x5f0 drivers/tty/vt/vt.c:664
> Read of size 2 at addr ffff888000100000 by task (agetty)/17350
> 
> CPU: 6 PID: 17350 Comm: (agetty) Not tainted 5.11.0-rc1+ #3

Wait, that's a VERY old and obsolete and known buggy kernel version.
Please test with something more modern, usually Linus's tree, or
linux-next or worst case, the latest stable release.  5.11-rc1 came out
almost 2 years ago, and over 150 thousand changes have happened since
then.

Not much we really can do about old obsolete kernels, sorry.

thanks,

greg k-h