tcp: correct read of TFO keys on big endian systems

When TFO keys are read back on big endian systems either via the global
sysctl interface or via getsockopt() using TCP_FASTOPEN_KEY, the values
don't match what was written.

For example, on s390x:

# echo "1-2-3-4" > /proc/sys/net/ipv4/tcp_fastopen_key
# cat /proc/sys/net/ipv4/tcp_fastopen_key
02000000-01000000-04000000-03000000

Instead of:

# cat /proc/sys/net/ipv4/tcp_fastopen_key
00000001-00000002-00000003-00000004

Fix this by converting to the correct endianness on read. This was
reported by Colin Ian King when running the 'tcp_fastopen_backup_key' net
selftest on s390x, which depends on the read value matching what was
written. I've confirmed that the test now passes on big and little endian
systems.

Signed-off-by: Jason Baron <jbaron@akamai.com>
Fixes: 438ac88009bc ("net: fastopen: robustness and endianness fixes for SipHash")
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Eric Dumazet <edumazet@google.com>
Reported-and-tested-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/tcp.h b/include/net/tcp.h
index dbf5c79..eab6c75 100644 (file)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1672,6 +1672,8 @@ void tcp_fastopen_destroy_cipher(struct sock *sk);
 void tcp_fastopen_ctx_destroy(struct net *net);
 int tcp_fastopen_reset_cipher(struct net *net, struct sock *sk,
                              void *primary_key, void *backup_key);
+int tcp_fastopen_get_cipher(struct net *net, struct inet_connection_sock *icsk,
+                           u64 *key);
 void tcp_fastopen_add_skb(struct sock *sk, struct sk_buff *skb);
 struct sock *tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
                              struct request_sock *req,

diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 5653e3b..54023a4 100644 (file)
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -301,24 +301,16 @@ static int proc_tcp_fastopen_key(struct ctl_table *table, int write,
        struct ctl_table tbl = { .maxlen = ((TCP_FASTOPEN_KEY_LENGTH *
                                            2 * TCP_FASTOPEN_KEY_MAX) +
                                            (TCP_FASTOPEN_KEY_MAX * 5)) };
-       struct tcp_fastopen_context *ctx;
-       u32 user_key[TCP_FASTOPEN_KEY_MAX * 4];
-       __le32 key[TCP_FASTOPEN_KEY_MAX * 4];
+       u32 user_key[TCP_FASTOPEN_KEY_BUF_LENGTH / sizeof(u32)];
+       __le32 key[TCP_FASTOPEN_KEY_BUF_LENGTH / sizeof(__le32)];
        char *backup_data;
-       int ret, i = 0, off = 0, n_keys = 0;
+       int ret, i = 0, off = 0, n_keys;
 
        tbl.data = kmalloc(tbl.maxlen, GFP_KERNEL);
        if (!tbl.data)
                return -ENOMEM;
 
-       rcu_read_lock();
-       ctx = rcu_dereference(net->ipv4.tcp_fastopen_ctx);
-       if (ctx) {
-               n_keys = tcp_fastopen_context_len(ctx);
-               memcpy(&key[0], &ctx->key[0], TCP_FASTOPEN_KEY_LENGTH * n_keys);
-       }
-       rcu_read_unlock();
-
+       n_keys = tcp_fastopen_get_cipher(net, NULL, (u64 *)key);
        if (!n_keys) {
                memset(&key[0], 0, TCP_FASTOPEN_KEY_LENGTH);
                n_keys = 1;

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index c06d2bf..31f3b85 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3685,22 +3685,14 @@ static int do_tcp_getsockopt(struct sock *sk, int level,
                return 0;
 
        case TCP_FASTOPEN_KEY: {
-               __u8 key[TCP_FASTOPEN_KEY_BUF_LENGTH];
-               struct tcp_fastopen_context *ctx;
-               unsigned int key_len = 0;
+               u64 key[TCP_FASTOPEN_KEY_BUF_LENGTH / sizeof(u64)];
+               unsigned int key_len;
 
                if (get_user(len, optlen))
                        return -EFAULT;
 
-               rcu_read_lock();
-               ctx = rcu_dereference(icsk->icsk_accept_queue.fastopenq.ctx);
-               if (ctx) {
-                       key_len = tcp_fastopen_context_len(ctx) *
-                                       TCP_FASTOPEN_KEY_LENGTH;
-                       memcpy(&key[0], &ctx->key[0], key_len);
-               }
-               rcu_read_unlock();
-
+               key_len = tcp_fastopen_get_cipher(net, icsk, key) *
+                               TCP_FASTOPEN_KEY_LENGTH;
                len = min_t(unsigned int, len, key_len);
                if (put_user(len, optlen))
                        return -EFAULT;

diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
index 19ad958..1bb8582 100644 (file)
--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -108,6 +108,29 @@ out:
        return err;
 }
 
+int tcp_fastopen_get_cipher(struct net *net, struct inet_connection_sock *icsk,
+                           u64 *key)
+{
+       struct tcp_fastopen_context *ctx;
+       int n_keys = 0, i;
+
+       rcu_read_lock();
+       if (icsk)
+               ctx = rcu_dereference(icsk->icsk_accept_queue.fastopenq.ctx);
+       else
+               ctx = rcu_dereference(net->ipv4.tcp_fastopen_ctx);
+       if (ctx) {
+               n_keys = tcp_fastopen_context_len(ctx);
+               for (i = 0; i < n_keys; i++) {
+                       put_unaligned_le64(ctx->key[i].key[0], key + (i * 2));
+                       put_unaligned_le64(ctx->key[i].key[1], key + (i * 2) + 1);
+               }
+       }
+       rcu_read_unlock();
+
+       return n_keys;
+}
+
 static bool __tcp_fastopen_cookie_gen_cipher(struct request_sock *req,
                                             struct sk_buff *syn,
                                             const siphash_key_t *key,