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

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Date:   Mon, 23 May 2022 17:34:26 +0100
From:   Luís Henriques <lhenriques@...e.de>
To:     Jeff Layton <jlayton@...nel.org>
Cc:     Xiubo Li <xiubli@...hat.com>, 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

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.

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

Cheers,
-- 
Luís