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 X-Spam-Level: X-Spam-Status: No, score=-8.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, FREEMAIL_REPLYTO_END_DIGIT,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F3D4DC43441 for ; Sat, 24 Nov 2018 01:54:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 91B1820824 for ; Sat, 24 Nov 2018 01:54:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b="L2h/gIm+" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 91B1820824 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=163.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729261AbeKXMlG (ORCPT ); Sat, 24 Nov 2018 07:41:06 -0500 Received: from m12-13.163.com ([220.181.12.13]:58618 "EHLO m12-13.163.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729235AbeKXMlG (ORCPT ); Sat, 24 Nov 2018 07:41:06 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=Date:From:Subject:Message-ID:MIME-Version; bh=Mia71 0GVrkzIa0+UQuBOddn+CcnraMEfxnPJ31GICwg=; b=L2h/gIm+dr74pezFFWqeR JRV1UuUTdpoEx2mBiIbLgKiQ+TmmkEIQY74gzvWBtcpwY7BygWVGrKKireEUT9D2 Jdxgn1jkbiLcX8Uy7sorYz4kiekHsk8Z3e7CWNN9kHbQmvt6LZzMiQDXttee30Px UTgv+kEPgJJMnMSbvsrP0A= Received: from bp (unknown [106.120.213.96]) by smtp9 (Coremail) with SMTP id DcCowAAnZcpOr_hbiqcSBg--.18944S2; Sat, 24 Nov 2018 09:54:22 +0800 (CST) Date: Sat, 24 Nov 2018 09:54:23 +0800 From: PanBian To: Viacheslav Dubeyko Cc: Joe Perches , Ernesto =?iso-8859-1?Q?A=2E_Fern=E1ndez?= , Andrew Morton , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] hfs: do not free node before using Message-ID: <20181124015423.GB23256@bp> Reply-To: PanBian References: <1542963889-128825-1-git-send-email-bianpan2016@163.com> <1543020709.12764.3.camel@dubeyko.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1543020709.12764.3.camel@dubeyko.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-CM-TRANSID: DcCowAAnZcpOr_hbiqcSBg--.18944S2 X-Coremail-Antispam: 1Uf129KBjvJXoW7tw1DGF47Xw1DXF4DKw45ZFb_yoW8Wr17pr yxCF42kF4DZ34IkrnavF1Fg34vyw4xJrs0kws5Cr1xZ3Z8Xr97Wr18KryY93W5ZrW8Z3yj qrs8G3sxWrsxZaDanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07jNjjgUUUUU= X-Originating-IP: [106.120.213.96] X-CM-SenderInfo: held01tdqsiiqw6rljoofrz/xtbBzw4JclaD0ZEAlgAAs5 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 23, 2018 at 04:51:49PM -0800, Viacheslav Dubeyko wrote: > On Fri, 2018-11-23 at 17:04 +0800, Pan Bian wrote: > > The function hfs_bmap_free frees node via hfs_bnode_put(node). > > However, > > it then reads node->this when dumping error message on an error path, > > which may result in a use-after-free bug. This patch frees node only > > when it is never used. > > > > Fixes: d614267329f("hfs/hfsplus: convert printks to pr_") > > > > Signed-off-by: Pan Bian > > --- > >  fs/hfs/btree.c | 3 ++- > >  1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/fs/hfs/btree.c b/fs/hfs/btree.c > > index 98b96ff..19017d2 100644 > > --- a/fs/hfs/btree.c > > +++ b/fs/hfs/btree.c > > @@ -338,13 +338,14 @@ void hfs_bmap_free(struct hfs_bnode *node) > >   > >   nidx -= len * 8; > >   i = node->next; > > - hfs_bnode_put(node); > >   if (!i) { > >   /* panic */; > >   pr_crit("unable to free bnode %u. bmap not > > found!\n", > >   node->this); > > > What's about simply to store node->this into the local variable in the > beginning of the cycle? In this case, it is possible to use the node ID > in the pr_crit() and to use the hfs_bnode_put(node) in the same place > without to use it twice. What do you think? Of course, it is a solution. But I think doing like that does not really simplify the code, as we have to declare an extra local variable, and assign node->this to it... Best, Pan > > Thanks, > Vyacheslav Dubeyko. > > > > + hfs_bnode_put(node); > >   return; > >   } > > + hfs_bnode_put(node); > >   node = hfs_bnode_find(tree, i); > >   if (IS_ERR(node)) > >   return;