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Date: Tue, 28 Jul 2020 11:59:14 -0700
From: Eric Biggers <>
Subject: Re: [CVE-2020-14331] Linux Kernel: buffer over write
 in vgacon_scrollback_update

On Tue, Jul 28, 2020 at 11:16:55AM +0800, 张云海 wrote:
> There is a buffer over write in drivers/video/console/vgacon.c in
> vgacon_scrollback_update.
> The issue is reported by Yunhai Zhang / NSFOCUS Security Team
> <>, CVE-2020-14331 assigned via Red Hat.
> # Affected Versions
> The issue is found and tested on 5.7.0-rc6.
> The issue is introduced in commit:
> 15bdab959c9bb909c0317480dd9b35748a8f7887 ([PATCH] vgacon: Add support
> for soft scrollback)
> According to code review, all versions older than
> 92ed301919932f777713b9172e525674157e983d (v5.8-rc7) are affected.

Thanks for the writeup.  Note that there are many open syzbot reports in the
fbdev, vt, and vgacon kernel subsystems.  These subsystems aren't actively
maintained (receiving drive-by fixes only), and the kernel developers recommend
to not enable these subsystems if you care about security

This particular bug, for example, appears to have been already found by someone
running syzkaller and publicly reported over 2 years ago, with a C reproducer:
No one did anything.

I suggest that people relying on the security of these kernel subsystems
contribute resources to fixing the many known fuzzing bugs in them.

- Eric

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