net: dccp: fix kernel crash on module load

Patch eedbbb0d "net: dccp: initialize (addr,port) ..."
added calling to inet_hashinfo2_init() from dccp_init().

However, inet_hashinfo2_init() is marked as __init(), and
thus the kernel panics when dccp is loaded as module. Removing
__init() tag from inet_hashinfo2_init() is not feasible because
it calls into __init functions in mm.

This patch adds inet_hashinfo2_init_mod() function that can
be called after the init phase is done; changes dccp_init() to
call the new function; un-marks inet_hashinfo2_init() as
exported.

Fixes: eedbbb0d ("net: dccp: initialize (addr,port) ...")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Peter Oskolkov <posk@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/inet_hashtables.h

@@ -237,6 +237,7 @@ void inet_hashinfo2_init(struct inet_hashinfo *h, const char *name,
 			 unsigned long numentries, int scale,
 			 unsigned long low_limit,
 			 unsigned long high_limit);
+int inet_hashinfo2_init_mod(struct inet_hashinfo *h);
 
 bool inet_ehash_insert(struct sock *sk, struct sock *osk);
 bool inet_ehash_nolisten(struct sock *sk, struct sock *osk);

net/dccp/proto.c

@@ -1139,11 +1139,11 @@ static int __init dccp_init(void)
 	rc = percpu_counter_init(&dccp_orphan_count, 0, GFP_KERNEL);
 	if (rc)
 		goto out_fail;
-	rc = -ENOBUFS;
 	inet_hashinfo_init(&dccp_hashinfo);
-	inet_hashinfo2_init(&dccp_hashinfo, "dccp_listen_portaddr_hash",
-			    INET_LHTABLE_SIZE, 21,  /* one slot per 2 MB*/
-			    0, 64 * 1024);
+	rc = inet_hashinfo2_init_mod(&dccp_hashinfo);
+	if (rc)
+		goto out_fail;
+	rc = -ENOBUFS;
 	dccp_hashinfo.bind_bucket_cachep =
 		kmem_cache_create("dccp_bind_bucket",
 				  sizeof(struct inet_bind_bucket), 0,

net/ipv4/inet_hashtables.c

@@ -762,13 +762,22 @@ void inet_hashinfo_init(struct inet_hashinfo *h)
 }
 EXPORT_SYMBOL_GPL(inet_hashinfo_init);
 
+static void init_hashinfo_lhash2(struct inet_hashinfo *h)
+{
+	int i;
+
+	for (i = 0; i <= h->lhash2_mask; i++) {
+		spin_lock_init(&h->lhash2[i].lock);
+		INIT_HLIST_HEAD(&h->lhash2[i].head);
+		h->lhash2[i].count = 0;
+	}
+}
+
 void __init inet_hashinfo2_init(struct inet_hashinfo *h, const char *name,
 				unsigned long numentries, int scale,
 				unsigned long low_limit,
 				unsigned long high_limit)
 {
-	unsigned int i;
-
 	h->lhash2 = alloc_large_system_hash(name,
 					    sizeof(*h->lhash2),
 					    numentries,
@@ -778,14 +787,23 @@ void __init inet_hashinfo2_init(struct inet_hashinfo *h, const char *name,
 					    &h->lhash2_mask,
 					    low_limit,
 					    high_limit);
+	init_hashinfo_lhash2(h);
+}
 
-	for (i = 0; i <= h->lhash2_mask; i++) {
-		spin_lock_init(&h->lhash2[i].lock);
-		INIT_HLIST_HEAD(&h->lhash2[i].head);
-		h->lhash2[i].count = 0;
-	}
+int inet_hashinfo2_init_mod(struct inet_hashinfo *h)
+{
+	h->lhash2 = kmalloc_array(INET_LHTABLE_SIZE, sizeof(*h->lhash2), GFP_KERNEL);
+	if (!h->lhash2)
+		return -ENOMEM;
+
+	h->lhash2_mask = INET_LHTABLE_SIZE - 1;
+	/* INET_LHTABLE_SIZE must be a power of 2 */
+	BUG_ON(INET_LHTABLE_SIZE & h->lhash2_mask);
+
+	init_hashinfo_lhash2(h);
+	return 0;
 }
-EXPORT_SYMBOL_GPL(inet_hashinfo2_init);
+EXPORT_SYMBOL_GPL(inet_hashinfo2_init_mod);
 
 int inet_ehash_locks_alloc(struct inet_hashinfo *hashinfo)
 {