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

[Xiubo Li]

On 5/24/22 12:34 AM, Luís Henriques wrote:
> Jeff Layton <jlayton@xxxxxxxxxx> 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@xxxxxxx>
> > > ---
> > >   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@xxxxxxxxxx>
> Cheers,