[TCP]: Fix MD5 signature handling on big-endian.

Based upon a report and initial patch by Peter Lieven.

tcp4_md5sig_key and tcp6_md5sig_key need to start with
the exact same members as tcp_md5sig_key. Because they
are both cast to that type by tcp_v{4,6}_md5_do_lookup().

Unfortunately tcp{4,6}_md5sig_key use a u16 for the key
length instead of a u8, which is what tcp_md5sig_key
uses. This just so happens to work by accident on
little-endian, but on big-endian it doesn't.

Instead of casting, just place tcp_md5sig_key as the first member of
the address-family specific structures, adjust the access sites, and
kill off the ugly casts.

Signed-off-by: David S. Miller <[e-mail]>

include/net/tcp.h

···
 };
 
 struct tcp4_md5sig_key {
-	u8			*key;
-	u16			keylen;
+	struct tcp_md5sig_key	base;
 	__be32			addr;
 };
 
 struct tcp6_md5sig_key {
-	u8			*key;
-	u16			keylen;
+	struct tcp_md5sig_key	base;
 #if 0
 	u32			scope_id;	/* XXX */
 #endif

net/ipv4/tcp_ipv4.c

···
 		return NULL;
 	for (i = 0; i < tp->md5sig_info->entries4; i++) {
 		if (tp->md5sig_info->keys4[i].addr == addr)
-			return (struct tcp_md5sig_key *)
-						&tp->md5sig_info->keys4[i];
+			return &tp->md5sig_info->keys4[i].base;
 	}
 	return NULL;
 }
···
 	key = (struct tcp4_md5sig_key *)tcp_v4_md5_do_lookup(sk, addr);
 	if (key) {
 		/* Pre-existing entry - just update that one. */
-		kfree(key->key);
-		key->key = newkey;
-		key->keylen = newkeylen;
+		kfree(key->base.key);
+		key->base.key = newkey;
+		key->base.keylen = newkeylen;
 	} else {
 		struct tcp_md5sig_info *md5sig;
 
···
 			md5sig->alloced4++;
 		}
 		md5sig->entries4++;
-		md5sig->keys4[md5sig->entries4 - 1].addr   = addr;
-		md5sig->keys4[md5sig->entries4 - 1].key    = newkey;
-		md5sig->keys4[md5sig->entries4 - 1].keylen = newkeylen;
+		md5sig->keys4[md5sig->entries4 - 1].addr        = addr;
+		md5sig->keys4[md5sig->entries4 - 1].base.key    = newkey;
+		md5sig->keys4[md5sig->entries4 - 1].base.keylen = newkeylen;
 	}
 	return 0;
 }
···
 	for (i = 0; i < tp->md5sig_info->entries4; i++) {
 		if (tp->md5sig_info->keys4[i].addr == addr) {
 			/* Free the key */
-			kfree(tp->md5sig_info->keys4[i].key);
+			kfree(tp->md5sig_info->keys4[i].base.key);
 			tp->md5sig_info->entries4--;
 
 			if (tp->md5sig_info->entries4 == 0) {
···
 	if (tp->md5sig_info->entries4) {
 		int i;
 		for (i = 0; i < tp->md5sig_info->entries4; i++)
-			kfree(tp->md5sig_info->keys4[i].key);
+			kfree(tp->md5sig_info->keys4[i].base.key);
 		tp->md5sig_info->entries4 = 0;
 		tcp_free_md5sig_pool();
 	}

net/ipv6/tcp_ipv6.c

···
 
 	for (i = 0; i < tp->md5sig_info->entries6; i++) {
 		if (ipv6_addr_cmp(&tp->md5sig_info->keys6[i].addr, addr) == 0)
-			return (struct tcp_md5sig_key *)&tp->md5sig_info->keys6[i];
+			return &tp->md5sig_info->keys6[i].base;
 	}
 	return NULL;
 }
···
 	key = (struct tcp6_md5sig_key*) tcp_v6_md5_do_lookup(sk, peer);
 	if (key) {
 		/* modify existing entry - just update that one */
-		kfree(key->key);
-		key->key = newkey;
-		key->keylen = newkeylen;
+		kfree(key->base.key);
+		key->base.key = newkey;
+		key->base.keylen = newkeylen;
 	} else {
 		/* reallocate new list if current one is full. */
 		if (!tp->md5sig_info) {
···
 
 		ipv6_addr_copy(&tp->md5sig_info->keys6[tp->md5sig_info->entries6].addr,
 			       peer);
-		tp->md5sig_info->keys6[tp->md5sig_info->entries6].key = newkey;
-		tp->md5sig_info->keys6[tp->md5sig_info->entries6].keylen = newkeylen;
+		tp->md5sig_info->keys6[tp->md5sig_info->entries6].base.key = newkey;
+		tp->md5sig_info->keys6[tp->md5sig_info->entries6].base.keylen = newkeylen;
 
 		tp->md5sig_info->entries6++;
 	}
···
 	for (i = 0; i < tp->md5sig_info->entries6; i++) {
 		if (ipv6_addr_cmp(&tp->md5sig_info->keys6[i].addr, peer) == 0) {
 			/* Free the key */
-			kfree(tp->md5sig_info->keys6[i].key);
+			kfree(tp->md5sig_info->keys6[i].base.key);
 			tp->md5sig_info->entries6--;
 
 			if (tp->md5sig_info->entries6 == 0) {
···
 
 	if (tp->md5sig_info->entries6) {
 		for (i = 0; i < tp->md5sig_info->entries6; i++)
-			kfree(tp->md5sig_info->keys6[i].key);
+			kfree(tp->md5sig_info->keys6[i].base.key);
 		tp->md5sig_info->entries6 = 0;
 		tcp_free_md5sig_pool();
 	}
···
 
 	if (tp->md5sig_info->entries4) {
 		for (i = 0; i < tp->md5sig_info->entries4; i++)
-			kfree(tp->md5sig_info->keys4[i].key);
+			kfree(tp->md5sig_info->keys4[i].base.key);
 		tp->md5sig_info->entries4 = 0;
 		tcp_free_md5sig_pool();
 	}