dlm: fix overflows when copying from ->m_extra to lvb

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David Teigland <teigland@redhat.com>

fs/dlm/lock.c

@@ -1226,6 +1226,8 @@ static void set_lvb_lock_pc(struct dlm_rsb *r, struct dlm_lkb *lkb,
 	b = dlm_lvb_operations[lkb->lkb_grmode + 1][lkb->lkb_rqmode + 1];
 	if (b == 1) {
 		int len = receive_extralen(ms);
+		if (len > DLM_RESNAME_MAXLEN)
+			len = DLM_RESNAME_MAXLEN;
 		memcpy(lkb->lkb_lvbptr, ms->m_extra, len);
 		lkb->lkb_lvbseq = ms->m_lvbseq;
 	}
@@ -2993,6 +2995,8 @@ static int receive_lvb(struct dlm_ls *ls, struct dlm_lkb *lkb,
 		if (!lkb->lkb_lvbptr)
 			return -ENOMEM;
 		len = receive_extralen(ms);
+		if (len > DLM_RESNAME_MAXLEN)
+			len = DLM_RESNAME_MAXLEN;
 		memcpy(lkb->lkb_lvbptr, ms->m_extra, len);
 	}
 	return 0;