flask: fix gcov build with gcc14+

Gcc's "threading" of conditionals can lead to undue warnings, as reported
in e.g. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116519 (no matter
that the overall situation is different there). While my gcc15 complains
("buf[2] may be used uninitialized in this function") about only two of
the three instances (not about the one in type_read()), adjust all three
to be on the safe side.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Daniel P. Smith <dpsmith@apertussolutions.com>

xen/xsm/flask/ss/policydb.c

@@ -1271,7 +1271,10 @@ static int cf_check role_read(struct policydb *p, struct hashtab *h, void *fp)
     if ( ver >= POLICYDB_VERSION_BOUNDARY )
         rc = next_entry(buf, fp, sizeof(buf[0]) * 3);
     else
+    {
         rc = next_entry(buf, fp, sizeof(buf[0]) * 2);
+        buf[2] = cpu_to_le32(0); /* gcc14 onwards */
+    }
 
     if ( rc < 0 )
         goto bad;
@@ -1342,7 +1345,10 @@ static int cf_check type_read(struct policydb *p, struct hashtab *h, void *fp)
     if ( ver >= POLICYDB_VERSION_BOUNDARY )
         rc = next_entry(buf, fp, sizeof(buf[0]) * 4);
     else
+    {
         rc = next_entry(buf, fp, sizeof(buf[0]) * 3);
+        buf[3] = cpu_to_le32(0); /* gcc14 onwards */
+    }
 
     if ( rc < 0 )
         goto bad;
@@ -1436,7 +1442,10 @@ static int cf_check user_read(struct policydb *p, struct hashtab *h, void *fp)
     if ( ver >= POLICYDB_VERSION_BOUNDARY )
         rc = next_entry(buf, fp, sizeof(buf[0]) * 3);
     else
+    {
         rc = next_entry(buf, fp, sizeof(buf[0]) * 2);
+        buf[2] = cpu_to_le32(0); /* gcc14 onwards */
+    }
 
     if ( rc < 0 )
         goto bad;