pppoatm: take ATM socket lock in pppoatm_send()

The pppoatm_send() does not take any lock that will prevent concurrent
vcc_sendmsg(). This causes two problems:

	- there is no locking between checking the send queue size
	  with atm_may_send() and incrementing sk_wmem_alloc,
	  and the real queue size can be a little higher than sk_sndbuf

	- the vcc->sendmsg() can be called concurrently. I'm not sure
	  if it's allowed. Some drivers (eni, nicstar, ...) seem
	  to assume it will never happen.

Now pppoatm_send() takes ATM socket lock, the same that is used
in vcc_sendmsg() and other ATM socket functions. The pppoatm_send()
is called with BH disabled, so bh_lock_sock() is used instead
of lock_sock().

Signed-off-by: Krzysztof Mazur <krzysiek@podlesie.net>
Cc: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

1 files changed, 17 insertions, 2 deletions

diff --git a/net/atm/pppoatm.c b/net/atm/pppoatm.c
index b23c6723e87c..c4a57bca77bf 100644
--- a/net/atm/pppoatm.c
+++ b/net/atm/pppoatm.c
@@ -272,10 +272,19 @@ static inline int pppoatm_may_send(struct pppoatm_vcc *pvcc, int size)
 static int pppoatm_send(struct ppp_channel *chan, struct sk_buff *skb)
 {
         struct pppoatm_vcc *pvcc = chan_to_pvcc(chan);
+        struct atm_vcc *vcc;
+        int ret;
+
         ATM_SKB(skb)->vcc = pvcc->atmvcc;
         pr_debug("(skb=0x%p, vcc=0x%p)\n", skb, pvcc->atmvcc);
         if (skb->data[0] == '\0' && (pvcc->flags & SC_COMP_PROT))
                 (void) skb_pull(skb, 1);
+
+        vcc = ATM_SKB(skb)->vcc;
+        bh_lock_sock(sk_atm(vcc));
+        if (sock_owned_by_user(sk_atm(vcc)))
+                goto nospace;
+
         switch (pvcc->encaps) {         /* LLC encapsulation needed */
         case e_llc:
                 if (skb_headroom(skb) < LLC_LEN) {
@@ -288,8 +297,10 @@ static int pppoatm_send(struct ppp_channel *chan, struct sk_buff *skb)
                         }
                         consume_skb(skb);
                         skb = n;
-                        if (skb == NULL)
+                        if (skb == NULL) {
+                                bh_unlock_sock(sk_atm(vcc));
                                 return DROP_PACKET;
+                        }
                 } else if (!pppoatm_may_send(pvcc, skb->truesize))
                         goto nospace;
                 memcpy(skb_push(skb, LLC_LEN), pppllc, LLC_LEN);
@@ -299,6 +310,7 @@ static int pppoatm_send(struct ppp_channel *chan, struct sk_buff *skb)
                         goto nospace;
                 break;
         case e_autodetect:
+                bh_unlock_sock(sk_atm(vcc));
                 pr_debug("Trying to send without setting encaps!\n");
                 kfree_skb(skb);
                 return 1;
@@ -308,9 +320,12 @@ static int pppoatm_send(struct ppp_channel *chan, struct sk_buff *skb)
         ATM_SKB(skb)->atm_options = ATM_SKB(skb)->vcc->atm_options;
         pr_debug("atm_skb(%p)->vcc(%p)->dev(%p)\n",
                  skb, ATM_SKB(skb)->vcc, ATM_SKB(skb)->vcc->dev);
-        return ATM_SKB(skb)->vcc->send(ATM_SKB(skb)->vcc, skb)
+        ret = ATM_SKB(skb)->vcc->send(ATM_SKB(skb)->vcc, skb)
             ? DROP_PACKET : 1;
+        bh_unlock_sock(sk_atm(vcc));
+        return ret;
 nospace:
+        bh_unlock_sock(sk_atm(vcc));
         /*
          * We don't have space to send this SKB now, but we might have
          * already applied SC_COMP_PROT compression, so may need to undo