linux-kernel - [PATCH 5.15 863/917] ceph: fix mdsmap decode when there are MDSs beyond max

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Message-Id: <20211115165458.290802129@linuxfoundation.org>
Date:   Mon, 15 Nov 2021 18:05:58 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Xiubo Li <xiubli@...hat.com>,
        Jeff Layton <jlayton@...nel.org>,
        Ilya Dryomov <idryomov@...il.com>
Subject: [PATCH 5.15 863/917] ceph: fix mdsmap decode when there are MDSs beyond max_mds

From: Xiubo Li <xiubli@...hat.com>

commit 0e24421ac431e7af62d4acef6c638b85aae51728 upstream.

If the max_mds is decreased in a cephfs cluster, there is a window
of time before the MDSs are removed. If a map goes out during this
period, the mdsmap may show the decreased max_mds but still shows
those MDSes as in or in the export target list.

Ensure that we don't fail the map decode in that case.

Cc: stable@...r.kernel.org
URL: https://tracker.ceph.com/issues/52436
Fixes: d517b3983dd3 ("ceph: reconnect to the export targets on new mdsmaps")
Signed-off-by: Xiubo Li <xiubli@...hat.com>
Reviewed-by: Jeff Layton <jlayton@...nel.org>
Signed-off-by: Ilya Dryomov <idryomov@...il.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/ceph/mdsmap.c |    4 ----
 1 file changed, 4 deletions(-)

--- a/fs/ceph/mdsmap.c
+++ b/fs/ceph/mdsmap.c
@@ -263,10 +263,6 @@ struct ceph_mdsmap *ceph_mdsmap_decode(v
 				goto nomem;
 			for (j = 0; j < num_export_targets; j++) {
 				target = ceph_decode_32(&pexport_targets);
-				if (target >= m->possible_max_rank) {
-					err = -EIO;
-					goto corrupt;
-				}
 				info->export_targets[j] = target;
 			}
 		} else {