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 2734E355024; Tue, 6 Jan 2026 17:23:33 +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=1767720213; cv=none; b=gjI13TR6uD2Khz+19bYnLORduHZS1Ybu2DeGM1PHNiBIXgzYZPH/JpaLJUir7BLLkYWO+R2otIgEJkYdXPOicrV3U6it0dfoQkXtuWXCEd2kIR/3K30Tff7gYMtYlNv7B/oRL7nnNI2cR2V5HhsyqqORV12LFS4naiJgbJpEzkY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767720213; c=relaxed/simple; bh=LY2AI6ZIQLCoJb8ydPBHHRcPUWqSUIgGFcamYxhsbIw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=OuF0G3ODq+ks0VPn4TEe+jK4Il3da19tgQLo/HqzEPS+2urlHLDYr8RP5jWfIwyYRmlbUq9Y+MHN+nG8EldSldiFXdEzMlYngGEbtnMFUkrHu8kNUYzkrMoi3gY72i6Zpz2OU8+sGP40TjPGKDpuehNsAYuun1t9Q9VH5J07SPw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=rM2n9SOQ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="rM2n9SOQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 90A05C16AAE; Tue, 6 Jan 2026 17:23:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1767720213; bh=LY2AI6ZIQLCoJb8ydPBHHRcPUWqSUIgGFcamYxhsbIw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=rM2n9SOQHAmdrwuRztE8r4ht29RNNQMEx/zL9gJm1YYq3+0tzY+7q8GvKQZoURTLi 8bFyaCxo4UDQRiK2Djw6dtFJjVCVAsst0VgB7WNDzmZDYQFLR8UtP3rBZPUKB9jsSD jqpNeikMwd2SKZ6F6QUEEnbiDNVdh+Txb26whaug= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Fedor Pchelkin , Baokun Li , Jan Kara , Theodore Tso Subject: [PATCH 6.12 167/567] ext4: fix string copying in parse_apply_sb_mount_options() Date: Tue, 6 Jan 2026 17:59:09 +0100 Message-ID: <20260106170457.504395100@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260106170451.332875001@linuxfoundation.org> References: <20260106170451.332875001@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Fedor Pchelkin commit ee5a977b4e771cc181f39d504426dbd31ed701cc upstream. 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 Signed-off-by: Greg Kroah-Hartman --- fs/ext4/super.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -2493,7 +2493,7 @@ static int parse_apply_sb_mount_options( struct ext4_fs_context *m_ctx) { struct ext4_sb_info *sbi = EXT4_SB(sb); - char s_mount_opts[65]; + char s_mount_opts[64]; struct ext4_fs_context *s_ctx = NULL; struct fs_context *fc = NULL; int ret = -ENOMEM; @@ -2501,7 +2501,8 @@ static int parse_apply_sb_mount_options( if (!sbi->s_es->s_mount_opts[0]) return 0; - strscpy_pad(s_mount_opts, sbi->s_es->s_mount_opts); + if (strscpy_pad(s_mount_opts, sbi->s_es->s_mount_opts) < 0) + return -E2BIG; fc = kzalloc(sizeof(struct fs_context), GFP_KERNEL); if (!fc)