linux-kernel - Re: [PATCH 4.4 48/76] libceph: force GFP

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAOi1vP-TeEwNM8n=Z5b6yx1epMDVJ4f7+S1poubA7zfT7L0hQQ@mail.gmail.com>
Date:   Tue, 28 Mar 2017 15:23:58 +0200
From:   Ilya Dryomov <idryomov@...il.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        stable@...r.kernel.org, Sergey Jerusalimov <wintchester@...il.com>,
        Jeff Layton <jlayton@...hat.com>
Subject: Re: [PATCH 4.4 48/76] libceph: force GFP_NOIO for socket allocations

On Tue, Mar 28, 2017 at 2:43 PM, Michal Hocko <mhocko@...nel.org> wrote:
> On Tue 28-03-17 14:30:45, Greg KH wrote:
>> 4.4-stable review patch.  If anyone has any objections, please let me know.
>
> I haven't seen the original patch but the changelog makes me worried.
> How exactly this is a problem? Where do we lockup? Does rbd/libceph take
> any xfs locks?

No, it doesn't.  This is just another instance of "using GFP_KERNEL on
the writeback path may lead to a deadlock" with nothing extra to it.

XFS is writing out data, libceph messenger worker tries to open
a socket and recurses back into XFS because the sockfs inode is
allocated with GFP_KERNEL.  The message with some of the data never
goes out and eventually we get a deadlock.

I've only included the offending stack trace.  I guess I should have
stressed that ceph-msgr workqueue is used for reclaim.

Thanks,

                Ilya