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Subject[PATCH 3.18 106/185] llc: properly handle dev_queue_xmit() return value
Date
3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Cong Wang <xiyou.wangcong@gmail.com>

[ Upstream commit b85ab56c3f81c5a24b5a5213374f549df06430da ]

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>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/net/llc_conn.h | 2 +-
net/llc/llc_c_ac.c | 15 +++++++++------
net/llc/llc_conn.c | 32 +++++++++++++++++++++++---------
3 files changed, 33 insertions(+), 16 deletions(-)

--- a/include/net/llc_conn.h
+++ b/include/net/llc_conn.h
@@ -104,7 +104,7 @@ 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);
--- 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_
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_
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_
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;
}

/**
--- 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
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
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 so
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;
}

/**

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