Phonet: fix flawed "SYN/ACK" logic

* Do not fail if the peer supports more or less than 3 algorithms.
 * Ignore unknown congestion control algorithms instead of failing.
 * Simplify congestion algorithm negotiation (largest is best).
 * Do not use a static buffer.
 * Fix off-by-two read overflow.
 * Avoid extra memory copy (in addition to skb_copy_bits()).

The previous code really made no sense.

Signed-off-by: Rémi Denis-Courmont <remi.denis-courmont@nokia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/phonet/pep.h b/include/net/phonet/pep.h
index 37f23dc..38eed1b 100644 (file)
--- a/include/net/phonet/pep.h
+++ b/include/net/phonet/pep.h
@@ -154,6 +154,7 @@ enum {
        PN_LEGACY_FLOW_CONTROL,
        PN_ONE_CREDIT_FLOW_CONTROL,
        PN_MULTI_CREDIT_FLOW_CONTROL,
+       PN_MAX_FLOW_CONTROL,
 };
 
 #define pn_flow_safe(fc) ((fc) >> 1)

diff --git a/net/phonet/pep.c b/net/phonet/pep.c
index 0ecab59..b8c31fc 100644 (file)
--- a/net/phonet/pep.c
+++ b/net/phonet/pep.c
@@ -108,70 +108,6 @@ static int pep_reply(struct sock *sk, struct sk_buff *oskb,
 #define PAD 0x00
 
 #ifdef CONFIG_PHONET_PIPECTRLR
-static u8 pipe_negotiate_fc(u8 *host_fc, u8 *remote_fc, int len)
-{
-       int i, j;
-       u8 base_fc, final_fc;
-
-       for (i = 0; i < len; i++) {
-               base_fc = host_fc[i];
-               for (j = 0; j < len; j++) {
-                       if (remote_fc[j] == base_fc) {
-                               final_fc = base_fc;
-                               goto done;
-                       }
-               }
-       }
-       return -EINVAL;
-
-done:
-       return final_fc;
-
-}
-
-static int pipe_get_flow_info(struct sock *sk, struct sk_buff *skb,
-               u8 *pref_rx_fc, u8 *req_tx_fc)
-{
-       struct pnpipehdr *hdr;
-       u8 n_sb;
-
-       if (!pskb_may_pull(skb, sizeof(*hdr) + 4))
-               return -EINVAL;
-
-       hdr = pnp_hdr(skb);
-       n_sb = hdr->data[4];
-
-       __skb_pull(skb, sizeof(*hdr) + 4);
-       while (n_sb > 0) {
-               u8 type, buf[3], len = sizeof(buf);
-               u8 *data = pep_get_sb(skb, &type, &len, buf);
-
-               if (data == NULL)
-                       return -EINVAL;
-
-               switch (type) {
-               case PN_PIPE_SB_REQUIRED_FC_TX:
-                       if (len < 3 || (data[2] | data[3] | data[4]) > 3)
-                               break;
-                       req_tx_fc[0] = data[2];
-                       req_tx_fc[1] = data[3];
-                       req_tx_fc[2] = data[4];
-                       break;
-
-               case PN_PIPE_SB_PREFERRED_FC_RX:
-                       if (len < 3 || (data[2] | data[3] | data[4]) > 3)
-                               break;
-                       pref_rx_fc[0] = data[2];
-                       pref_rx_fc[1] = data[3];
-                       pref_rx_fc[2] = data[4];
-                       break;
-
-               }
-               n_sb--;
-       }
-       return 0;
-}
-
 static int pipe_handler_send_req(struct sock *sk, u8 msg_id, gfp_t priority)
 {
        int len;
@@ -661,28 +597,61 @@ static void pipe_destruct(struct sock *sk)
 }
 
 #ifdef CONFIG_PHONET_PIPECTRLR
+static u8 pipe_negotiate_fc(const u8 *fcs, unsigned n)
+{
+       unsigned i;
+       u8 final_fc = PN_NO_FLOW_CONTROL;
+
+       for (i = 0; i < n; i++) {
+               u8 fc = fcs[i];
+
+               if (fc > final_fc && fc < PN_MAX_FLOW_CONTROL)
+                       final_fc = fc;
+       }
+       return final_fc;
+}
+
 static int pep_connresp_rcv(struct sock *sk, struct sk_buff *skb)
 {
        struct pep_sock *pn = pep_sk(sk);
-       u8 host_pref_rx_fc[3] = {3, 2, 1}, host_req_tx_fc[3] = {3, 2, 1};
-       u8 remote_pref_rx_fc[3], remote_req_tx_fc[3];
-       u8 negotiated_rx_fc, negotiated_tx_fc;
-
-       pipe_get_flow_info(sk, skb, remote_pref_rx_fc,
-                       remote_req_tx_fc);
-       negotiated_tx_fc = pipe_negotiate_fc(remote_req_tx_fc,
-                       host_pref_rx_fc,
-                       sizeof(host_pref_rx_fc));
-       negotiated_rx_fc = pipe_negotiate_fc(host_req_tx_fc,
-                       remote_pref_rx_fc,
-                       sizeof(host_pref_rx_fc));
+       struct pnpipehdr *hdr;
+       u8 n_sb;
+
+       if (!pskb_pull(skb, sizeof(*hdr) + 4))
+               return -EINVAL;
+
+       hdr = pnp_hdr(skb);
+
+       /* Parse sub-blocks */
+       n_sb = hdr->data[4];
+       while (n_sb > 0) {
+               u8 type, buf[6], len = sizeof(buf);
+               const u8 *data = pep_get_sb(skb, &type, &len, buf);
+
+               if (data == NULL)
+                       return -EINVAL;
+
+               switch (type) {
+               case PN_PIPE_SB_REQUIRED_FC_TX:
+                       if (len < 2 || len < data[0])
+                               break;
+                       pn->tx_fc = pipe_negotiate_fc(data + 2, len - 2);
+                       break;
+
+               case PN_PIPE_SB_PREFERRED_FC_RX:
+                       if (len < 2 || len < data[0])
+                               break;
+                       pn->rx_fc = pipe_negotiate_fc(data + 2, len - 2);
+                       break;
+
+               }
+               n_sb--;
+       }
 
        sk->sk_state = TCP_SYN_RECV;
        sk->sk_backlog_rcv = pipe_do_rcv;
        sk->sk_destruct = pipe_destruct;
        pn->rx_credits = 0;
-       pn->rx_fc = negotiated_rx_fc;
-       pn->tx_fc = negotiated_tx_fc;
        sk->sk_state_change(sk);
 
        return pipe_handler_send_created_ind(sk, PNS_PIPE_CREATED_IND);