linux-kernel - Re: [PATCH] ceph: fix decoding of client session messages flags

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Message-ID: <3a5e1fdc-6ace-d4bc-7bca-20854155d652@redhat.com>
Date:   Tue, 24 May 2022 09:20:02 +0800
From:   Xiubo Li <xiubli@...hat.com>
To:     Luís Henriques <lhenriques@...e.de>,
        Jeff Layton <jlayton@...nel.org>
Cc:     Ilya Dryomov <idryomov@...il.com>, ceph-devel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ceph: fix decoding of client session messages flags


On 5/24/22 12:34 AM, Luís Henriques wrote:
> Jeff Layton <jlayton@...nel.org> writes:
>
>> On Mon, 2022-05-23 at 17:09 +0100, Luís Henriques wrote:
>>> The cephfs kernel client started to show  the message:
>>>
>>>   ceph: mds0 session blocklisted
>>>
>>> when mounting a filesystem.  This is due to the fact that the session
>>> messages are being incorrectly decoded: the skip needs to take into
>>> account the 'len'.
>>>
>>> While there, fixed some whitespaces too.
>>>
>>> Fixes: e1c9788cb397 ("ceph: don't rely on error_string to validate blocklisted session.")
>>> Signed-off-by: Luís Henriques <lhenriques@...e.de>
>>> ---
>>>   fs/ceph/mds_client.c | 14 +++++++++-----
>>>   1 file changed, 9 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
>>> index 00c3de177dd6..1bd3e1bb0fdf 100644
>>> --- a/fs/ceph/mds_client.c
>>> +++ b/fs/ceph/mds_client.c
>>> @@ -3375,13 +3375,17 @@ static void handle_session(struct ceph_mds_session *session,
>>>   	}
>>>   
>>>   	if (msg_version >= 5) {
>>> -		u32 flags;
>>> -		/* version >= 4, struct_v, struct_cv, len, metric_spec */
>>> -	        ceph_decode_skip_n(&p, end, 2 + sizeof(u32) * 2, bad);
>>> +		u32 flags, len;
>>> +
>>> +		/* version >= 4 */
>>> +		ceph_decode_skip_16(&p, end, bad); /* struct_v, struct_cv */
>>> +		ceph_decode_32_safe(&p, end, len, bad); /* len */
>>> +		ceph_decode_skip_n(&p, end, len, bad); /* metric_spec */
>>> +
>>>   		/* version >= 5, flags   */
>>> -                ceph_decode_32_safe(&p, end, flags, bad);
>>> +		ceph_decode_32_safe(&p, end, flags, bad);
>>>   		if (flags & CEPH_SESSION_BLOCKLISTED) {
>>> -		        pr_warn("mds%d session blocklisted\n", session->s_mds);
>>> +			pr_warn("mds%d session blocklisted\n", session->s_mds);
>>>   			blocklisted = true;
>>>   		}
>>>   	}
>> Good catch! Should we send this to stable too?
> Ah, yeah.  I didn't explicitly tagged it as I assumed the 'Fixes:' would
> be enough for that.  But it's probably better to do add the 'Cc: stable'
> too.

Good catch! Merged into the testing branch and added the 'Cc: stable'.

Thanks Luis.

-- Xiubo


>> Reviewed-by: Jeff Layton <jlayton@...nel.org>
> Cheers,