From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6B7CAC54EBC for ; Tue, 20 Dec 2022 01:26:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233439AbiLTB0K (ORCPT ); Mon, 19 Dec 2022 20:26:10 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52420 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233193AbiLTBXh (ORCPT ); Mon, 19 Dec 2022 20:23:37 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3D4E311151; Mon, 19 Dec 2022 17:22:15 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id D9D3CB810FA; Tue, 20 Dec 2022 01:22:13 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 670EDC433F1; Tue, 20 Dec 2022 01:22:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1671499332; bh=aQFaecaqcH30nHzpU+8RbcjuDn2x7otmuRN7p6ZP31U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UEdaG28PR9Ggzi62AGfzP82yi4L577sT4Sywz9kPTvV7nWZlkOD0boZWWbSJdRi3a NhA2zOYwmMNAqJGKo1Rvsy5qfQSAfPi4uyeC7WNHiH02vgQCH3vuZVLf5ut/1kbru/ 5PxMpKzbJkl1lQzwYr0OJVjf040ssqiF3kE2wDzv6pnLJ+efLEVXmd1YaBP82FEYjc 7Q4u+EfAETGE+W+Y0aaBw4hqQI2IJctttAbuFISzv0AEWsOGUopuwQepqqNnDT+USK VqL2A0XEzAxzlP31MyTPnVCLF4OKHw04xFldaOGpaeya6ImRBA7xEhOb0DqzltJsJo OCbBPjCtVYnDQ== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Hawkins Jiawei , syzbot+a3e6acd85ded5c16a709@syzkaller.appspotmail.com, Mike Kravetz , Muchun Song , Ian Kent , Andrew Morton , Sasha Levin , muchun.song@linux.dev, linux-mm@kvack.org Subject: [PATCH AUTOSEL 5.15 5/9] hugetlbfs: fix null-ptr-deref in hugetlbfs_parse_param() Date: Mon, 19 Dec 2022 20:21:55 -0500 Message-Id: <20221220012159.1222517-5-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20221220012159.1222517-1-sashal@kernel.org> References: <20221220012159.1222517-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Hawkins Jiawei [ Upstream commit 26215b7ee923b9251f7bb12c4e5f09dc465d35f2 ] Syzkaller reports a null-ptr-deref bug as follows: ====================================================== KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] RIP: 0010:hugetlbfs_parse_param+0x1dd/0x8e0 fs/hugetlbfs/inode.c:1380 [...] Call Trace: vfs_parse_fs_param fs/fs_context.c:148 [inline] vfs_parse_fs_param+0x1f9/0x3c0 fs/fs_context.c:129 vfs_parse_fs_string+0xdb/0x170 fs/fs_context.c:191 generic_parse_monolithic+0x16f/0x1f0 fs/fs_context.c:231 do_new_mount fs/namespace.c:3036 [inline] path_mount+0x12de/0x1e20 fs/namespace.c:3370 do_mount fs/namespace.c:3383 [inline] __do_sys_mount fs/namespace.c:3591 [inline] __se_sys_mount fs/namespace.c:3568 [inline] __x64_sys_mount+0x27f/0x300 fs/namespace.c:3568 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd [...] ====================================================== According to commit "vfs: parse: deal with zero length string value", kernel will set the param->string to null pointer in vfs_parse_fs_string() if fs string has zero length. Yet the problem is that, hugetlbfs_parse_param() will dereference the param->string, without checking whether it is a null pointer. To be more specific, if hugetlbfs_parse_param() parses an illegal mount parameter, such as "size=,", kernel will constructs struct fs_parameter with null pointer in vfs_parse_fs_string(), then passes this struct fs_parameter to hugetlbfs_parse_param(), which triggers the above null-ptr-deref bug. This patch solves it by adding sanity check on param->string in hugetlbfs_parse_param(). Link: https://lkml.kernel.org/r/20221020231609.4810-1-yin31149@gmail.com Reported-by: syzbot+a3e6acd85ded5c16a709@syzkaller.appspotmail.com Tested-by: syzbot+a3e6acd85ded5c16a709@syzkaller.appspotmail.com Link: https://lore.kernel.org/all/0000000000005ad00405eb7148c6@google.com/ Signed-off-by: Hawkins Jiawei Reviewed-by: Mike Kravetz Cc: Hawkins Jiawei Cc: Muchun Song Cc: Ian Kent Signed-off-by: Andrew Morton Signed-off-by: Sasha Levin --- fs/hugetlbfs/inode.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index be8deec29ebe..352230a011e0 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -1250,7 +1250,7 @@ static int hugetlbfs_parse_param(struct fs_context *fc, struct fs_parameter *par case Opt_size: /* memparse() will accept a K/M/G without a digit */ - if (!isdigit(param->string[0])) + if (!param->string || !isdigit(param->string[0])) goto bad_val; ctx->max_size_opt = memparse(param->string, &rest); ctx->max_val_type = SIZE_STD; @@ -1260,7 +1260,7 @@ static int hugetlbfs_parse_param(struct fs_context *fc, struct fs_parameter *par case Opt_nr_inodes: /* memparse() will accept a K/M/G without a digit */ - if (!isdigit(param->string[0])) + if (!param->string || !isdigit(param->string[0])) goto bad_val; ctx->nr_inodes = memparse(param->string, &rest); return 0; @@ -1276,7 +1276,7 @@ static int hugetlbfs_parse_param(struct fs_context *fc, struct fs_parameter *par case Opt_min_size: /* memparse() will accept a K/M/G without a digit */ - if (!isdigit(param->string[0])) + if (!param->string || !isdigit(param->string[0])) goto bad_val; ctx->min_size_opt = memparse(param->string, &rest); ctx->min_val_type = SIZE_STD; -- 2.35.1