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 B164DC38A2D for ; Fri, 21 Oct 2022 20:43:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230026AbiJUUnB (ORCPT ); Fri, 21 Oct 2022 16:43:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45086 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230424AbiJUUmT (ORCPT ); Fri, 21 Oct 2022 16:42:19 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 63EADBB076 for ; Fri, 21 Oct 2022 13:41:52 -0700 (PDT) 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 4138CB80C82 for ; Fri, 21 Oct 2022 20:41:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 97720C433D7; Fri, 21 Oct 2022 20:41:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1666384908; bh=Qzg0lzb4PyXJJpKafhb5Mq85PLuLiXUJJpeNDuwXkKM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=ReshceG5rp6LLS2X4EjA3hNe+xtJmtSeqLaGBy4fLcsKbO0DOWo7r0Axsge39E7rp Bs6rMoys5yCI8c/5Hn6n8ygTleU67IOhzfAhdNN2uwZ3Md0UmFDpGiDWtPJBdqL0rj aPnDajP6SSLCjixdJ65PrIzlZq4bjdlDe+Ec1SDI= Date: Fri, 21 Oct 2022 13:41:47 -0700 From: Andrew Morton To: Mike Kravetz Cc: Hawkins Jiawei , syzbot+a3e6acd85ded5c16a709@syzkaller.appspotmail.com, Muchun Song , linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, 18801353760@163.com, Ian Kent Subject: Re: [PATCH -next] hugetlbfs: fix null-ptr-deref in hugetlbfs_parse_param() Message-Id: <20221021134147.17278fc73dce36589d167c5d@linux-foundation.org> In-Reply-To: References: <20221020231609.4810-1-yin31149@gmail.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 20 Oct 2022 16:38:18 -0700 Mike Kravetz wrote: > On 10/21/22 07:16, Hawkins Jiawei wrote: > > 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 > > ac369cdd9448("vfs: parse: deal with zero length string value"), > > kernel will sets 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(). > > > > 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 > > Thank you! > > This was on my list of things to look at. > > Do you know if the issue existed before commit ac369cdd9448? Just > wondering if we need a Fixes tag and stable backports. Ian Kent's "vfs: parse: deal with zero length string value" exists only in mm-nonmm-unstable. I'm hoping that it gets some attention from Al Viro. I'll merge this patch so we're ready for Ian's patch. I normally merge mm-stable ahead of mm-nonmm-stable so there shouldn't be a bisection window. Ian, could you please go through the filesystems and see if there are other instances of this getting ready to bite us? > I'll take a closer look at the patch a bit later, unless someone beats > me to it. > -- > Mike Kravetz > > > --- > > 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 7f836f8f9db1..3ee84604e36d 100644 > > --- a/fs/hugetlbfs/inode.c > > +++ b/fs/hugetlbfs/inode.c > > @@ -1377,7 +1377,7 @@ 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; > > @@ -1387,7 +1387,7 @@ 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; > > @@ -1403,7 +1403,7 @@ 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; > > -- > > 2.25.1 > >