linux-ext4 - Re: [PATCH] ext4: Reject on-disk mount options with missing NUL-terminator

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Message-ID: <202602101749.40E8AB05@keescook>
Date: Tue, 10 Feb 2026 17:50:00 -0800
From: Kees Cook <kees@...nel.org>
To: Fedor Pchelkin <pchelkin@...ras.ru>
Cc: "Darrick J. Wong" <djwong@...nel.org>, Theodore Ts'o <tytso@....edu>,
	李龙兴 <coregee2000@...il.com>,
	Andreas Dilger <adilger.kernel@...ger.ca>,
	Andy Shevchenko <andriy.shevchenko@...el.com>,
	linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org, Jan Kara <jack@...e.cz>
Subject: Re: [PATCH] ext4: Reject on-disk mount options with missing
 NUL-terminator

On Tue, Feb 10, 2026 at 12:03:35PM +0300, Fedor Pchelkin wrote:
> If I understand the issue correctly, it's already being rejected with the
> existing check:
> 
> 	if (strscpy_pad(s_mount_opts, sbi->s_es->s_mount_opts) < 0)
> 		return -E2BIG;
> 
> If the source string is truncated at least by one symbol (which is the
> case for unterminated string), strscpy_pad() returns -E2BIG and the mount
> fails.

Agreed. Sorry for the noise! Things appear to be fine as-is. I had
missed the version tested in the original report.

-- 
Kees Cook