5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Raphael Zimmer commit 40480eee361ed9676b3f844d532ac28b47251634 upstream. A message of type CEPH_MSG_MON_MAP contains a monmap that is sent from a monitor to the client. This monmap contains information about the existing monitors in the cluster. Currently, a monmap indicating that there are zero monitors in the cluster is treated as valid. However, it is impossible to have zero monitors in the cluster and still receive a valid monmap from a monitor. Therefore, such a monmap must be corrupted and should be treated as invalid. Furthermore, a monmap with a monitor count of zero can subsequently crash the client when attempting to open a session with a monitor in __open_session(). This happens because the "BUG_ON(monc->monmap->num_mon < 1)" assertion in pick_new_mon() is triggered. This patch extends a check in ceph_monmap_decode() to also reject arriving mon_maps with num_mon == 0 rather than only with num_mon > CEPH_MAX_MON. [ idryomov: drop "log output for unusual values of num_mon" part ] Signed-off-by: Raphael Zimmer Reviewed-by: Ilya Dryomov Signed-off-by: Ilya Dryomov Signed-off-by: Roman Demidov Signed-off-by: Sasha Levin --- net/ceph/mon_client.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ceph/mon_client.c b/net/ceph/mon_client.c index e1f01aef263e8..fac52fe7a5870 100644 --- a/net/ceph/mon_client.c +++ b/net/ceph/mon_client.c @@ -59,7 +59,7 @@ static struct ceph_monmap *ceph_monmap_decode(void *p, void *end) num_mon = ceph_decode_32(&p); - if (num_mon > CEPH_MAX_MON) + if (num_mon == 0 || num_mon > CEPH_MAX_MON) goto bad; m = kmalloc(struct_size(m, mon_inst, num_mon), GFP_NOFS); if (m == NULL) -- 2.53.0