tcp: switch tcp_fastopen key generation to net_get_random_once
Changed key initialization of tcp_fastopen cookies to net_get_random_once.
If the user sets a custom key net_get_random_once must be called at
least once to ensure we don't overwrite the user provided key when the
first cookie is generated later on.
Cc: Yuchung Cheng <ycheng@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
index ab7bd35..766032b 100644
--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -14,6 +14,20 @@
static DEFINE_SPINLOCK(tcp_fastopen_ctx_lock);
+void tcp_fastopen_init_key_once(bool publish)
+{
+ static u8 key[TCP_FASTOPEN_KEY_LENGTH];
+
+ /* tcp_fastopen_reset_cipher publishes the new context
+ * atomically, so we allow this race happening here.
+ *
+ * All call sites of tcp_fastopen_cookie_gen also check
+ * for a valid cookie, so this is an acceptable risk.
+ */
+ if (net_get_random_once(key, sizeof(key)) && publish)
+ tcp_fastopen_reset_cipher(key, sizeof(key));
+}
+
static void tcp_fastopen_ctx_free(struct rcu_head *head)
{
struct tcp_fastopen_context *ctx =
@@ -70,6 +84,8 @@
__be32 path[4] = { src, dst, 0, 0 };
struct tcp_fastopen_context *ctx;
+ tcp_fastopen_init_key_once(true);
+
rcu_read_lock();
ctx = rcu_dereference(tcp_fastopen_ctx);
if (ctx) {
@@ -78,14 +94,3 @@
}
rcu_read_unlock();
}
-
-static int __init tcp_fastopen_init(void)
-{
- __u8 key[TCP_FASTOPEN_KEY_LENGTH];
-
- get_random_bytes(key, sizeof(key));
- tcp_fastopen_reset_cipher(key, sizeof(key));
- return 0;
-}
-
-late_initcall(tcp_fastopen_init);