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

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Message-ID: <b88b5d86-21dc-428c-a514-9030ffd494a1@kernel.org>
Date: Wed, 9 Jul 2025 09:07:25 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Jiri Slaby <jirislaby@...nel.org>, Luka <luka.2016.cs@...il.com>
Cc: linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org
Subject: Re: [Bug] WARNING in vt_do_diacrit in Linux Kernel v6.14

On 08/07/2025 10:46, Jiri Slaby wrote:
> On 08. 07. 25, 9:21, 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.
>> Under conditions such as memory allocation failure or page table
>> unavailability, this leads to a fault during execution of the mov
>> %eax, (%rcx) instruction.
> 
> Which is exactly how it should behave, right? If #PF, then it jumps to 
> __put_user_handle_exception and returns EFAULT.
Jiri,
Don't waste time. It's AI generated spam. Same as before.

Best regards,
Krzysztof