From: Yuchung Cheng <ycheng@google.com>
Date: Wed, 27 Jun 2018 16:04:48 -0700
Subject: tcp: fix Fast Open key endianness
Git-commit: c860e997e9170a6d68f9d1e6e2cf61f572191aaf
Patch-mainline: v4.18-rc4
References: networking-stable-18_07_19

Fast Open key could be stored in different endian based on the CPU.
Previously hosts in different endianness in a server farm using
the same key config (sysctl value) would produce different cookies.
This patch fixes it by always storing it as little endian to keep
same API for LE hosts.

Reported-by: Daniele Iamartino <danielei@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 net/ipv4/sysctl_net_ipv4.c |   18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -257,8 +257,9 @@ static int proc_tcp_fastopen_key(struct
 {
 	struct ctl_table tbl = { .maxlen = (TCP_FASTOPEN_KEY_LENGTH * 2 + 10) };
 	struct tcp_fastopen_context *ctxt;
-	int ret;
 	u32  user_key[4]; /* 16 bytes, matching TCP_FASTOPEN_KEY_LENGTH */
+	__le32 key[4];
+	int ret, i;
 
 	tbl.data = kmalloc(tbl.maxlen, GFP_KERNEL);
 	if (!tbl.data)
@@ -267,11 +268,14 @@ static int proc_tcp_fastopen_key(struct
 	rcu_read_lock();
 	ctxt = rcu_dereference(tcp_fastopen_ctx);
 	if (ctxt)
-		memcpy(user_key, ctxt->key, TCP_FASTOPEN_KEY_LENGTH);
+		memcpy(key, ctxt->key, TCP_FASTOPEN_KEY_LENGTH);
 	else
-		memset(user_key, 0, sizeof(user_key));
+		memset(key, 0, sizeof(key));
 	rcu_read_unlock();
 
+	for (i = 0; i < ARRAY_SIZE(key); i++)
+		user_key[i] = le32_to_cpu(key[i]);
+
 	snprintf(tbl.data, tbl.maxlen, "%08x-%08x-%08x-%08x",
 		user_key[0], user_key[1], user_key[2], user_key[3]);
 	ret = proc_dostring(&tbl, write, buffer, lenp, ppos);
@@ -287,12 +291,16 @@ static int proc_tcp_fastopen_key(struct
 		 * first invocation of tcp_fastopen_cookie_gen
 		 */
 		tcp_fastopen_init_key_once(false);
-		tcp_fastopen_reset_cipher(user_key, TCP_FASTOPEN_KEY_LENGTH);
+
+		for (i = 0; i < ARRAY_SIZE(user_key); i++)
+			key[i] = cpu_to_le32(user_key[i]);
+
+		tcp_fastopen_reset_cipher(key, TCP_FASTOPEN_KEY_LENGTH);
 	}
 
 bad_key:
 	pr_debug("proc FO key set 0x%x-%x-%x-%x <- 0x%s: %u\n",
-	       user_key[0], user_key[1], user_key[2], user_key[3],
+		 user_key[0], user_key[1], user_key[2], user_key[3],
 	       (char *)tbl.data, ret);
 	kfree(tbl.data);
 	return ret;