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 D37AB1A58D for ; Tue, 30 Dec 2025 00:47:27 +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=1767055647; cv=none; b=l4XnXlERIl7boUo/Ymp1av0Apxj8EAB9xMDje1sNeBwUPA9bOOWuhOQxHlU3yNLsj+fim5I8Jidt1s6GZleXmYC3ZMb48iaXv7y2bC2U5IhX8DgJ6t3Dtg+KdTMHyyVMN9uTXXEWgcHq8wu23ucEeYHl3ft+GPTvsPSeCMOfwgU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767055647; c=relaxed/simple; bh=rJm57baL4IyLLZGgONDVMTHB8xgUv0qoC7DEW8U6JSg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=iR0ftw+gqC7pNUol64SdFXz6PMlF5XGhTL40G4EIUR/0ZkjffiUR6vMgFPYgs+/tMO4G+V8S5b2T6LtbZyIG2p7pGoDo+39fmmpMwRKCmf1ilwHV8Q2llN5o3udbwnt28HJaipWW3QQAi53ubefwMSqun+OcFj3O4dzd20ypn2A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ENtPmfMt; 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="ENtPmfMt" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BD170C4CEF7; Tue, 30 Dec 2025 00:47:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1767055647; bh=rJm57baL4IyLLZGgONDVMTHB8xgUv0qoC7DEW8U6JSg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ENtPmfMt5mL/I38H+3loOcD1zMpU74wBreYhFle0+E+WjAI0WcCnzMNqtFWHgTcv/ lvWx66ALdznfvLyW6WaToyizqkylLNRbZuqi2TRCU96Br2320HfjHJkwz5w8biU4I4 fOjMCPUvRgitS+MiIcntnucSXNz5S/RzryLHgYWkMojeh0SphKzb9TUu7/EEvZfM53 Y7M5Gz4jcANaeVLEJJTnvCmxOJezbdO7zdU++MM8PK7r28nteUJgLG+BhI1B13LllX KXguSNk1lWkIDF3QjMHa+VFhcCEVUTdv9G3yc5CQl/z0BnxSmPD4+8NZsZsK2ItEft 6wYBXoZxp58jg== From: Sasha Levin To: stable@vger.kernel.org Cc: Fedor Pchelkin , Baokun Li , Jan Kara , Theodore Ts'o , Sasha Levin Subject: [PATCH 6.6.y] ext4: fix string copying in parse_apply_sb_mount_options() Date: Mon, 29 Dec 2025 19:47:24 -0500 Message-ID: <20251230004724.1896388-1-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <2025122956-dropkick-outlast-5a49@gregkh> References: <2025122956-dropkick-outlast-5a49@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 [ adapted 2-argument strscpy_pad() call to 3-argument form with explicit sizeof() ] Signed-off-by: Sasha Levin --- fs/ext4/super.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 16a6c249580e..5f823ea4a20a 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -2506,7 +2506,7 @@ static int parse_apply_sb_mount_options(struct super_block *sb, 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; @@ -2514,7 +2514,8 @@ static int parse_apply_sb_mount_options(struct super_block *sb, if (!sbi->s_es->s_mount_opts[0]) return 0; - 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) + return -E2BIG; fc = kzalloc(sizeof(struct fs_context), GFP_KERNEL); if (!fc) -- 2.51.0