From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	Kefu Chai <k.chai@proxmox.com>,
	Ilya Dryomov <idryomov@gmail.com>
Subject: [PATCH 6.18 064/217] libceph: tolerate addrvecs with multiple entries of the same type
Date: Thu, 20 Aug 2026 16:53:52 +0200
Message-ID: <20260820145239.549940331@linuxfoundation.org>
In-Reply-To: <20260820145237.531699751@linuxfoundation.org>
References: <20260820145237.531699751@linuxfoundation.org>
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6.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Kefu Chai <k.chai@proxmox.com>

commit 5a87925539acecfe88229bad76ab81bd75a7e3f5 upstream.

ceph_decode_entity_addrvec() rejects any addrvec containing more than
one entry that matches the requested msgr type (LEGACY or MSGR2),
logging "another match of type N in addrvec" and returning -EINVAL.

Some admin tooling (e.g. pveceph mon create from Proxmox VE) generates
addrvecs with multiple same-type entries when public_network lists more
than one CIDR: it picks one local IP per subnet and emits both a v2 and
a v1 entry for each IP.  Monmaps shaped this way cause:

  libceph: mon0 (1)10.10.10.15:6789 session established
  libceph: another match of type 1 in addrvec
  libceph: problem decoding monmap, -22

No Ceph code uses the extra entries: since Nautilus, the userspace
messenger (AsyncMessenger) unconditionally picks the first address of
the requested type and ignores any subsequent matches.

Match that behavior: use the first matching entry and silently skip any
subsequent ones.  This is a compatibility fix for existing deployments
and does not enable dual-stack or multi-subnet address selection.

[ idryomov: tweak ceph_decode_entity_addrvec() comment ]

Cc: stable@vger.kernel.org
Fixes: a5cbd5fc22d5 ("libceph, ceph: get and handle cluster maps with addrvecs")
Link: https://bugzilla.proxmox.com/show_bug.cgi?id=7518
Signed-off-by: Kefu Chai <k.chai@proxmox.com>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ceph/decode.c |   18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

--- a/net/ceph/decode.c
+++ b/net/ceph/decode.c
@@ -87,8 +87,9 @@ bad:
 EXPORT_SYMBOL(ceph_decode_entity_addr);
 
 /*
- * Return addr of desired type (MSGR2 or LEGACY) or error.
- * Make sure there is only one match.
+ * Return addr of desired type (MSGR2 or LEGACY) or error.  In case of
+ * multiple matches, use the first one for compatibility with userspace
+ * messenger.
  *
  * Assume encoding with MSG_ADDR2.
  */
@@ -121,14 +122,13 @@ int ceph_decode_entity_addrvec(void **p,
 
 		dout("%s i %d addr %s\n", __func__, i, ceph_pr_addr(&tmp_addr));
 		if (tmp_addr.type == my_type) {
-			if (found) {
-				pr_err("another match of type %d in addrvec\n",
-				       le32_to_cpu(my_type));
-				return -EINVAL;
+			if (!found) {
+				memcpy(addr, &tmp_addr, sizeof(*addr));
+				found = true;
+			} else {
+				dout("%s skipping extra match of type %d in addrvec\n",
+				     __func__, le32_to_cpu(my_type));
 			}
-
-			memcpy(addr, &tmp_addr, sizeof(*addr));
-			found = true;
 		}
 	}