oss-sec mailing list archives
Re: CVE-2020-25656: Linux kernel concurrency UAF in vt_do_kdgkb_ioctl
From: Greg KH <gregkh () linuxfoundation org>
Date: Fri, 16 Oct 2020 09:03:49 +0200
On Fri, Oct 16, 2020 at 08:58:34AM +0200, Jiri Slaby wrote:
Cc Greg. On 16. 10. 20, 5:39, Minh Yuan wrote:Hi, We recently discovered a uaf read in vt_do_kdgkb_ioctl from linux kernel version 3.4 to the latest version (v5.9 for now). The root cause of this vulnerability is that there exits a race in KDGKBSENT and KDSKBSENT. Here are details: 1. use KDSKBSENT to allocate a lager heap buffer to funcbufptr; 2. use KDGKBSENT to obtain the allocated heap pointer in step1 by func_table, at the same time, due to KDGKBSENT has no lock, we can use KDSKBSENT again to allocate a larger buffer than step1, and the old funcbufptr will be freed. However, we've obtained the heap pointer in KDGKBSENT, so a uaf read will happen while executing put_user.Hi, this is likely the issue I am fixing at: https://git.kernel.org/pub/scm/linux/kernel/git/jirislaby/linux.git/commit/?h=devel&id=57c85191e788e172a446e34ef77d34473cfb1e8d I think, it won't apply cleanly as it's a part of a larger set. I will reorder the patch and send something during the day.
Great, thanks for looking into this! greg k-h
Current thread:
- CVE-2020-25656: Linux kernel concurrency UAF in vt_do_kdgkb_ioctl Minh Yuan (Oct 15)
- <Possible follow-ups>
- Re: CVE-2020-25656: Linux kernel concurrency UAF in vt_do_kdgkb_ioctl Jiri Slaby (Oct 16)
- Re: CVE-2020-25656: Linux kernel concurrency UAF in vt_do_kdgkb_ioctl Greg KH (Oct 16)