From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CB7BB1C4A24 for ; Tue, 30 Dec 2025 01:26:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767057976; cv=none; b=FdQ4qLFZEgl8a7VptAqII11JKYQg9oAqcydE6lFpac7uNJhKhFTeYTNi30Z63cfrqrcQGHQE3XsavupAFJ03tVggEMk0FRhHuJV5BWSoOH/flw9rd0osJOC+Q+xrqyfCtGQqRWJ3RZ30XdgWzXjWFr6l38QKNbjOwidUy8di0qA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767057976; c=relaxed/simple; bh=t9WZ/PCNlbtQdzauNE8oPBTv5i+Dis3yEXpYpdXD/os=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=E70LNZcj7VdATWuSLKj6lv3wUGmHFEzdytskxTuCkbSX2j/DOguycu5ETiANRj3EBetJ6iluv3kq2vmVQwEyPpLbSvAZ3RhuO+woGWW0c4QaQtvvrLGc5Y72h/iLNxsSM5FAwrS/o+iwfr38hwdx5eOzGBO8RM/gcSW7TxVZgsg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fdhhZRMO; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="fdhhZRMO" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 92D16C4CEF7; Tue, 30 Dec 2025 01:26:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1767057976; bh=t9WZ/PCNlbtQdzauNE8oPBTv5i+Dis3yEXpYpdXD/os=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fdhhZRMO+2GkmOCecHkR+iMsfPgT6z55R5niMlgU5q8kFSbYaRxlrPsn5KNeAktV+ tX1nF97gwrQhRYmOcbUGxM18IwTeE4t4jRu06IT7fZRuNI5GzFFRx78Rbhm15+H3lQ BQnQJTbeJgQd3c9aoqLeeKYenKRraStpeLEJ7WxLOzSkbX0wqX5I33XOIbOKyjJ+AD 14e2sVGH4GHG5x0MJTmUDO4UAGRqjlREb4BB9QSI5yw/y/cUSB/Fvv9B9shuBPRsMG XauWGteOb7U32JNldG9+tt7ST7gnc1d2rvE5Ehr3nr36nHzMokF0x9zM90AIhKZUXd u33zw80Bkh5wg== From: Sasha Levin To: stable@vger.kernel.org Cc: Fedor Pchelkin , Baokun Li , Jan Kara , Theodore Ts'o , Sasha Levin Subject: [PATCH 5.10.y] ext4: fix string copying in parse_apply_sb_mount_options() Date: Mon, 29 Dec 2025 20:26:14 -0500 Message-ID: <20251230012614.1920692-1-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <2025122959-unawake-devious-8898@gregkh> References: <2025122959-unawake-devious-8898@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Fedor Pchelkin [ Upstream commit ee5a977b4e771cc181f39d504426dbd31ed701cc ] strscpy_pad() can't be used to copy a non-NUL-term string into a NUL-term string of possibly bigger size. Commit 0efc5990bca5 ("string.h: Introduce memtostr() and memtostr_pad()") provides additional information in that regard. So if this happens, the following warning is observed: strnlen: detected buffer overflow: 65 byte read of buffer size 64 WARNING: CPU: 0 PID: 28655 at lib/string_helpers.c:1032 __fortify_report+0x96/0xc0 lib/string_helpers.c:1032 Modules linked in: CPU: 0 UID: 0 PID: 28655 Comm: syz-executor.3 Not tainted 6.12.54-syzkaller-00144-g5f0270f1ba00 #0 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:__fortify_report+0x96/0xc0 lib/string_helpers.c:1032 Call Trace: __fortify_panic+0x1f/0x30 lib/string_helpers.c:1039 strnlen include/linux/fortify-string.h:235 [inline] sized_strscpy include/linux/fortify-string.h:309 [inline] parse_apply_sb_mount_options fs/ext4/super.c:2504 [inline] __ext4_fill_super fs/ext4/super.c:5261 [inline] ext4_fill_super+0x3c35/0xad00 fs/ext4/super.c:5706 get_tree_bdev_flags+0x387/0x620 fs/super.c:1636 vfs_get_tree+0x93/0x380 fs/super.c:1814 do_new_mount fs/namespace.c:3553 [inline] path_mount+0x6ae/0x1f70 fs/namespace.c:3880 do_mount fs/namespace.c:3893 [inline] __do_sys_mount fs/namespace.c:4103 [inline] __se_sys_mount fs/namespace.c:4080 [inline] __x64_sys_mount+0x280/0x300 fs/namespace.c:4080 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0x64/0x140 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x76/0x7e Since userspace is expected to provide s_mount_opts field to be at most 63 characters long with the ending byte being NUL-term, use a 64-byte buffer which matches the size of s_mount_opts, so that strscpy_pad() does its job properly. Return with error if the user still managed to provide a non-NUL-term string here. Found by Linux Verification Center (linuxtesting.org) with Syzkaller. Fixes: 8ecb790ea8c3 ("ext4: avoid potential buffer over-read in parse_apply_sb_mount_options()") Cc: stable@vger.kernel.org Signed-off-by: Fedor Pchelkin Reviewed-by: Baokun Li Reviewed-by: Jan Kara Message-ID: <20251101160430.222297-1-pchelkin@ispras.ru> Signed-off-by: Theodore Ts'o [ goto failed_mount instead of return ] Signed-off-by: Sasha Levin --- fs/ext4/super.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 453e746ba361..41e49fee35e5 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -4282,10 +4282,11 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) } if (sbi->s_es->s_mount_opts[0]) { - char s_mount_opts[65]; + char s_mount_opts[64]; - strscpy_pad(s_mount_opts, sbi->s_es->s_mount_opts, - sizeof(s_mount_opts)); + if (strscpy_pad(s_mount_opts, sbi->s_es->s_mount_opts, + sizeof(s_mount_opts)) < 0) + goto failed_mount; if (!parse_options(s_mount_opts, sb, &journal_devnum, &journal_ioprio, 0)) { ext4_msg(sb, KERN_WARNING, -- 2.51.0