linux-kernel - Re: [Bug] WARNING in vt_do_diacrit in Linux Kernel v6.14

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <2025070805-stoning-overeager-39f1@gregkh>
Date: Tue, 8 Jul 2025 09:49:01 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Luka <luka.2016.cs@...il.com>
Cc: Jiri Slaby <jirislaby@...nel.org>, linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org
Subject: Re: [Bug] WARNING in vt_do_diacrit in Linux Kernel v6.14

On Tue, Jul 08, 2025 at 03:21:36PM +0800, Luka wrote:
> Dear Linux Kernel Maintainers,
> 
> I hope this message finds you well.
> 
> I am writing to report a potential vulnerability I encountered during
> testing of the Linux Kernel version v6.14.
> 
> Git Commit: 38fec10eb60d687e30c8c6b5420d86e8149f7557 (tag: v6.14)
> 
> Bug Location: drivers/tty/vt/keyboard.c
> 
> Bug report: https://pastebin.com/yuVJpati
> 
> Complete log: https://pastebin.com/qKnipvvK
> 
> Entire kernel config: https://pastebin.com/MRWGr3nv
> 
> Root Cause Analysis:
> The vt_do_diacrit() function in the virtual terminal subsystem
> performs a write to a user-space pointer via __put_user_4() without
> ensuring that the destination address is mapped and accessible.

Where?  I see calls to put_user() happening in that function, and the
return value is properly checked.  What lines exactly show the issue?

> Under conditions such as memory allocation failure or page table
> unavailability, this leads to a fault during execution of the mov
> %eax, (%rcx) instruction.

Again, a normal call to put_user() should be catching this.  Are you
sure you are looking at the latest kernel tree?

> At present, I have not yet obtained a minimal reproducer for this
> issue. However, I am actively working on reproducing it, and I will
> promptly share any additional findings or a working reproducer as soon
> as it becomes available.

Please do.

thanks,

greg k-h