linux-kernel - Re: [PATCH v2] ceph/iov_iter: fix bad iov_iter handling in ceph splice codepaths

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <CAOi1vP8Gu+Gc0+y8J5G9H14qGh=8o9SuHwYHKFQJgWy3vJQr8Q@mail.gmail.com>
Date:   Thu, 12 Jan 2017 12:46:42 +0100
From:   Ilya Dryomov <idryomov@...il.com>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     Jeff Layton <jlayton@...hat.com>, "Yan, Zheng" <zyan@...hat.com>,
        Sage Weil <sage@...hat.com>,
        Ceph Development <ceph-devel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Zhu, Caifeng" <zhucaifeng@...ssoft-nj.com>
Subject: Re: [PATCH v2] ceph/iov_iter: fix bad iov_iter handling in ceph
 splice codepaths

On Thu, Jan 12, 2017 at 12:37 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
> On Thu, Jan 12, 2017 at 12:13:31PM +0100, Ilya Dryomov wrote:
>
>> It would be a significant and wide-reaching change, but I've been
>> meaning to look into switching to iov_iter for a couple of releases
>> now.  There is a lot of ugly code in net/ceph/messenger.c to hangle
>> iteration over "page vectors", "page lists" and "bio lists".  All of it
>> predates iov_iter proliferation and is mostly incomplete anyway: IIRC
>> you can send out of a pagelist but can't recv into a pagelist, etc.
>
> Wait a sec...  Is it done from the same thread that has issued a syscall?
> If so, we certainly could just pass iov_iter without bothering with any
> form of ..._get_pages(); if not, we'll need at least to get from iovec
> to bio_vec, since userland addresses make sense only in the caller's
> context...

No, not necessarily - it's also used by rbd (all of net/ceph has two
users: fs/ceph and drivers/block/rbd.c).

Thanks,

                Ilya