From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751422AbdDAJLW (ORCPT ); Sat, 1 Apr 2017 05:11:22 -0400 Received: from mx2.suse.de ([195.135.220.15]:41727 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751095AbdDAJLU (ORCPT ); Sat, 1 Apr 2017 05:11:20 -0400 Subject: Re: [PATCHv2] fs: Handle register_shrinker failure To: Al Viro References: <1490342270-19240-1-git-send-email-nborisov@suse.com> <1490343948-20840-1-git-send-email-nborisov@suse.com> Cc: Dmitry Vyukov , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller@googlegroups.com From: Nikolay Borisov Message-ID: <7a5b5bb6-ef61-fad6-055a-cf026d0059ec@suse.com> Date: Sat, 1 Apr 2017 12:11:17 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: <1490343948-20840-1-git-send-email-nborisov@suse.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 24.03.2017 10:25, Nikolay Borisov wrote: > register_shrinker allocates dynamic memory and thus is susceptible to failures > under low-memory situation. Currently,get_userns ignores the return value of > register_shrinker, potentially exposing not fully initialised object. This > can lead to a NULL-ptr deref everytime shrinker->nr_deferred is referenced. > > Fix this by failing to register the filesystem in case there is not enough > memory to fully construct the shrinker object. > > Signed-off-by: Nikolay Borisov > Fixes: 1d3d4437eae1 ("vmscan: per-node deferred work") > Link: lkml.kernel.org/r/CACT4Y+b-purC3HHbw=SctmS3MA8FKqtNYZUS_KCo2WMctTwyNA@mail.gmail.com > --- PING, Al is there something bothering you with this patch that needs fixing before it's merged? Also I think it should be tagged stable. > > Add Fixes and Link tags for better traceability > > fs/super.c | 14 +++++++++++++- > 1 file changed, 13 insertions(+), 1 deletion(-) > > diff --git a/fs/super.c b/fs/super.c > index b8b6a086c03b..964b18447c92 100644 > --- a/fs/super.c > +++ b/fs/super.c > @@ -518,7 +518,19 @@ struct super_block *sget_userns(struct file_system_type *type, > hlist_add_head(&s->s_instances, &type->fs_supers); > spin_unlock(&sb_lock); > get_filesystem(type); > - register_shrinker(&s->s_shrink); > + err = register_shrinker(&s->s_shrink); > + if (err) { > + spin_lock(&sb_lock); > + list_del(&s->s_list); > + hlist_del(&s->s_instances); > + spin_unlock(&sb_lock); > + > + up_write(&s->s_umount); > + destroy_super(s); > + put_filesystem(type); > + return ERR_PTR(err); > + } > + > return s; > } > >