Messages in this thread Patch in this message | | | Date | Sat, 6 Oct 2012 17:38:04 +0200 | From | Krzysztof Mazur <> | Subject | Re: [PATCH] pppoatm: don't send frames to destroyed vcc |
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On Sat, Oct 06, 2012 at 02:32:50PM +0100, David Woodhouse wrote: > On Sat, 2012-10-06 at 14:19 +0200, Krzysztof Mazur wrote: > > Now pppoatm_send(), like vcc_sendmsg(), checks for vcc flags that > > indicate that vcc is not ready. > > And what locking prevents the flag from being set immediately after we > check it? >
nothing, this patch should fix this.
The vcc_sendmsg() uses lock_sock(sk). This lock is used by vcc_release(), so vcc_destroy_socket() will not be called between check and during ->send(). The vcc_release_async() sets ATM_VF_CLOSE, but it should be safe to call ->send() after it, because vcc->dev->ops->close() is not called.
The pppoatm_send() is called with bottom halfs disabled, so bh_lock_sock() should be used instead of lock_sock().
diff --git a/net/atm/pppoatm.c b/net/atm/pppoatm.c index 0dcb5dc..29afc68 100644 --- a/net/atm/pppoatm.c +++ b/net/atm/pppoatm.c @@ -270,6 +270,7 @@ 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); @@ -304,17 +305,22 @@ static int pppoatm_send(struct ppp_channel *chan, struct sk_buff *skb) } vcc = ATM_SKB(skb)->vcc; + bh_lock_sock(sk_atm(vcc)); if (test_bit(ATM_VF_RELEASED, &vcc->flags) || test_bit(ATM_VF_CLOSE, &vcc->flags) - || !test_bit(ATM_VF_READY, &vcc->flags)) + || !test_bit(ATM_VF_READY, &vcc->flags)) { + bh_unlock_sock(sk_atm(vcc)); goto nospace; + } atomic_add(skb->truesize, &sk_atm(ATM_SKB(skb)->vcc)->sk_wmem_alloc); 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: /* * We don't have space to send this SKB now, but we might have -- Krzysiek
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