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

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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,




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