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

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Date:   Fri, 28 Oct 2022 09:28:37 +0800
From:   Xiubo Li <xiubli@...hat.com>
To:     Luís Henriques <lhenriques@...e.de>,
        Ilya Dryomov <idryomov@...il.com>,
        Jeff Layton <jlayton@...nel.org>
Cc:     ceph-devel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ceph: fix mdsmap decode for v >= 17


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

Thanks!

- Xiubo