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Date: Tue, 10 Feb 2026 17:50:00 -0800
From: Kees Cook <kees@kernel.org>
To: Fedor Pchelkin <pchelkin@ispras.ru>
Cc: "Darrick J. Wong" <djwong@kernel.org>, Theodore Ts'o <tytso@mit.edu>,
	=?utf-8?B?5p2O6b6Z5YW0?= <coregee2000@gmail.com>,
	Andreas Dilger <adilger.kernel@dilger.ca>,
	Andy Shevchenko <andriy.shevchenko@intel.com>,
	linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-hardening@vger.kernel.org, Jan Kara <jack@suse.cz>
Subject: Re: [PATCH] ext4: Reject on-disk mount options with missing
 NUL-terminator
Message-ID: <202602101749.40E8AB05@keescook>
References: <20260206212654.work.035-kees@kernel.org>
 <20260209193945-80d9bfc8aa82b0eb1b764c7f-pchelkin@ispras>
 <202602091148.EDBFECE686@keescook>
 <20260210050124.GR7686@frogsfrogsfrogs>
 <20260210115731-8a60c77ca684b6684fb8955f-pchelkin@ispras>
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In-Reply-To: <20260210115731-8a60c77ca684b6684fb8955f-pchelkin@ispras>

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