linux-kernel - Re: [PATCH] ceph: fix mdsmap decode for v >= 17

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Message-ID: <Y1ubPgzSm7YATBRv@suse.de>
Date:   Fri, 28 Oct 2022 10:05:02 +0100
From:   Luís Henriques <lhenriques@...e.de>
To:     Xiubo Li <xiubli@...hat.com>
Cc:     Ilya Dryomov <idryomov@...il.com>,
        Jeff Layton <jlayton@...nel.org>, ceph-devel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ceph: fix mdsmap decode for v >= 17

On Fri, Oct 28, 2022 at 09:28:37AM +0800, Xiubo Li wrote:
> 
> On 27/10/2022 23:28, Luís Henriques wrote:
> > Commit d93231a6bc8a ("ceph: prevent a client from exceeding the MDS
> > maximum xattr size") was merged before the corresponding MDS-side changes
> > have been merged.  With the introduction of 'bal_rank_mask' in the mdsmap,
> > the decoding of maps with v>=17 is now incorrect.  Fix this by skipping
> > the 'bal_rank_mask' string decoding.
> > 
> > Fixes: d93231a6bc8a ("ceph: prevent a client from exceeding the MDS maximum xattr size")
> > Signed-off-by: Luís Henriques <lhenriques@...e.de>
> > ---
> > Hi!
> > 
> > This inconsistency was introduced by ceph PR #43284; I think that, before
> > picking this patch, we need to get PR #46357 merged to avoid new
> > problems.
> > 
> > Cheers,
> > --
> > Luís
> > 
> >   fs/ceph/mdsmap.c | 2 ++
> >   1 file changed, 2 insertions(+)
> > 
> > diff --git a/fs/ceph/mdsmap.c b/fs/ceph/mdsmap.c
> > index 3fbabc98e1f7..fe4f1a6c3465 100644
> > --- a/fs/ceph/mdsmap.c
> > +++ b/fs/ceph/mdsmap.c
> > @@ -379,6 +379,8 @@ struct ceph_mdsmap *ceph_mdsmap_decode(void **p, void *end, bool msgr2)
> >   		ceph_decode_skip_8(p, end, bad_ext);
> >   		/* required_client_features */
> >   		ceph_decode_skip_set(p, end, 64, bad_ext);
> > +		/* bal_rank_mask */
> > +		ceph_decode_skip_string(p, end, bad_ext);
> >   		ceph_decode_64_safe(p, end, m->m_max_xattr_size, bad_ext);
> >   	} else {
> >   		/* This forces the usage of the (sync) SETXATTR Op */
> > 
> Luis,
> 
> Because the ceph PR #43284 will break kclient here and your xattr size patch
> got merged long time ago, we should fix it in ceph. More detail please see
> my comments in:
> 
> https://github.com/ceph/ceph/pull/46357#issuecomment-1294290492

OK, agreed.  I'll update this PR to try to fix it on the MDS side
instead.  And let's try to have it merged as soon as possible to prevent
further issues.

Cheers,
--
Luís