llc: properly handle dev_queue_xmit() return value

llc_conn_send_pdu() pushes the skb into write queue and
calls llc_conn_send_pdus() to flush them out. However, the
status of dev_queue_xmit() is not returned to caller,
in this case, llc_conn_state_process().

llc_conn_state_process() needs hold the skb no matter
success or failure, because it still uses it after that,
therefore we should hold skb before dev_queue_xmit() when
that skb is the one being processed by llc_conn_state_process().

For other callers, they can just pass NULL and ignore
the return value as they are.

Reported-by: Noam Rathaus <noamr@beyondsecurity.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/llc_conn.h b/include/net/llc_conn.h
index fe994d2e52869d06be7d26b48b942e666e60f2da..5c40f118c0fad6448796579b01acba5f77e1e4fa 100644 (file)
--- a/include/net/llc_conn.h
+++ b/include/net/llc_conn.h
@@ -103,7 +103,7 @@ void llc_sk_reset(struct sock *sk);
 
 /* Access to a connection */
 int llc_conn_state_process(struct sock *sk, struct sk_buff *skb);
-void llc_conn_send_pdu(struct sock *sk, struct sk_buff *skb);
+int llc_conn_send_pdu(struct sock *sk, struct sk_buff *skb);
 void llc_conn_rtn_pdu(struct sock *sk, struct sk_buff *skb);
 void llc_conn_resend_i_pdu_as_cmd(struct sock *sk, u8 nr, u8 first_p_bit);
 void llc_conn_resend_i_pdu_as_rsp(struct sock *sk, u8 nr, u8 first_f_bit);

diff --git a/net/llc/llc_c_ac.c b/net/llc/llc_c_ac.c
index f59648018060f3bb40dc0c5ebc6cba1fd9c571b7..163121192acae1c88f6a81d7a594c189da3678da 100644 (file)
--- a/net/llc/llc_c_ac.c
+++ b/net/llc/llc_c_ac.c
@@ -389,7 +389,7 @@ static int llc_conn_ac_send_i_cmd_p_set_0(struct sock *sk, struct sk_buff *skb)
        llc_pdu_init_as_i_cmd(skb, 0, llc->vS, llc->vR);
        rc = llc_mac_hdr_init(skb, llc->dev->dev_addr, llc->daddr.mac);
        if (likely(!rc)) {
-               llc_conn_send_pdu(sk, skb);
+               rc = llc_conn_send_pdu(sk, skb);
                llc_conn_ac_inc_vs_by_1(sk, skb);
        }
        return rc;
@@ -916,7 +916,7 @@ static int llc_conn_ac_send_i_rsp_f_set_ackpf(struct sock *sk,
        llc_pdu_init_as_i_cmd(skb, llc->ack_pf, llc->vS, llc->vR);
        rc = llc_mac_hdr_init(skb, llc->dev->dev_addr, llc->daddr.mac);
        if (likely(!rc)) {
-               llc_conn_send_pdu(sk, skb);
+               rc = llc_conn_send_pdu(sk, skb);
                llc_conn_ac_inc_vs_by_1(sk, skb);
        }
        return rc;
@@ -935,14 +935,17 @@ static int llc_conn_ac_send_i_rsp_f_set_ackpf(struct sock *sk,
 int llc_conn_ac_send_i_as_ack(struct sock *sk, struct sk_buff *skb)
 {
        struct llc_sock *llc = llc_sk(sk);
+       int ret;
 
        if (llc->ack_must_be_send) {
-               llc_conn_ac_send_i_rsp_f_set_ackpf(sk, skb);
+               ret = llc_conn_ac_send_i_rsp_f_set_ackpf(sk, skb);
                llc->ack_must_be_send = 0 ;
                llc->ack_pf = 0;
-       } else
-               llc_conn_ac_send_i_cmd_p_set_0(sk, skb);
-       return 0;
+       } else {
+               ret = llc_conn_ac_send_i_cmd_p_set_0(sk, skb);
+       }
+
+       return ret;
 }
 
 /**

diff --git a/net/llc/llc_conn.c b/net/llc/llc_conn.c
index 9177dbb16dce22d46d390b4d48b191576d967452..110e32bcb39976c9e319329f6ca9ba5809614aa8 100644 (file)
--- a/net/llc/llc_conn.c
+++ b/net/llc/llc_conn.c
@@ -30,7 +30,7 @@
 #endif
 
 static int llc_find_offset(int state, int ev_type);
-static void llc_conn_send_pdus(struct sock *sk);
+static int llc_conn_send_pdus(struct sock *sk, struct sk_buff *skb);
 static int llc_conn_service(struct sock *sk, struct sk_buff *skb);
 static int llc_exec_conn_trans_actions(struct sock *sk,
                                       struct llc_conn_state_trans *trans,
@@ -193,11 +193,11 @@ out_skb_put:
        return rc;
 }
 
-void llc_conn_send_pdu(struct sock *sk, struct sk_buff *skb)
+int llc_conn_send_pdu(struct sock *sk, struct sk_buff *skb)
 {
        /* queue PDU to send to MAC layer */
        skb_queue_tail(&sk->sk_write_queue, skb);
-       llc_conn_send_pdus(sk);
+       return llc_conn_send_pdus(sk, skb);
 }
 
 /**
@@ -255,7 +255,7 @@ void llc_conn_resend_i_pdu_as_cmd(struct sock *sk, u8 nr, u8 first_p_bit)
        if (howmany_resend > 0)
                llc->vS = (llc->vS + 1) % LLC_2_SEQ_NBR_MODULO;
        /* any PDUs to re-send are queued up; start sending to MAC */
-       llc_conn_send_pdus(sk);
+       llc_conn_send_pdus(sk, NULL);
 out:;
 }
 
@@ -296,7 +296,7 @@ void llc_conn_resend_i_pdu_as_rsp(struct sock *sk, u8 nr, u8 first_f_bit)
        if (howmany_resend > 0)
                llc->vS = (llc->vS + 1) % LLC_2_SEQ_NBR_MODULO;
        /* any PDUs to re-send are queued up; start sending to MAC */
-       llc_conn_send_pdus(sk);
+       llc_conn_send_pdus(sk, NULL);
 out:;
 }
 
@@ -340,12 +340,16 @@ out:
 /**
  *     llc_conn_send_pdus - Sends queued PDUs
  *     @sk: active connection
+ *     @hold_skb: the skb held by caller, or NULL if does not care
  *
- *     Sends queued pdus to MAC layer for transmission.
+ *     Sends queued pdus to MAC layer for transmission. When @hold_skb is
+ *     NULL, always return 0. Otherwise, return 0 if @hold_skb is sent
+ *     successfully, or 1 for failure.
  */
-static void llc_conn_send_pdus(struct sock *sk)
+static int llc_conn_send_pdus(struct sock *sk, struct sk_buff *hold_skb)
 {
        struct sk_buff *skb;
+       int ret = 0;
 
        while ((skb = skb_dequeue(&sk->sk_write_queue)) != NULL) {
                struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb);
@@ -357,10 +361,20 @@ static void llc_conn_send_pdus(struct sock *sk)
                        skb_queue_tail(&llc_sk(sk)->pdu_unack_q, skb);
                        if (!skb2)
                                break;
-                       skb = skb2;
+                       dev_queue_xmit(skb2);
+               } else {
+                       bool is_target = skb == hold_skb;
+                       int rc;
+
+                       if (is_target)
+                               skb_get(skb);
+                       rc = dev_queue_xmit(skb);
+                       if (is_target)
+                               ret = rc;
                }
-               dev_queue_xmit(skb);
        }
+
+       return ret;
 }
 
 /**