CVE-2025-39880: libceph: fix invalid accesses to ceph_connection_v1_info

In the Linux kernel, the following vulnerability has been resolved:

libceph: fix invalid accesses to cephconnectionv1info

There is a place where generic code in messenger.c is reading and another place where it is writing to con->v1 union member without checking that the union member is active (i.e. msgr1 is in use).

On 64-bit systems, con->v1.authretry overlaps with con->v2.outiter, so such a read is almost guaranteed to return a bogus value instead of 0 when msgr2 is in use. This ends up being fairly benign because the side effect is just the invalidation of the authorizer and successive fetching of new tickets.

con->v1.connectseq overlaps with con->v2.connbufs and the fact that it's being written to can cause more serious consequences, but luckily it's not something that happens often.