Re: [PATCH] net: fix problem in reading sock TX queue

[David Miller <davem@davemloft.net>]

From: Tom Herbert <therbert@google.com>
Date: Wed, 14 Jul 2010 20:48:08 -0700 (PDT)

> Fix problem in reading the tx_queue recorded in a socket.  In
> dev_pick_tx, the TX queue is read by doing a check with
> sk_tx_queue_recorded on the socket, followed by a sk_tx_queue_get.
> The problem is that there is not mutual exclusion across these
> calls in the socket so it it is possible that the queue in the
> sock can be invalidated after sk_tx_queue_recorded is called so
> that sk_tx_queue get returns -1, which sets 65535 in queue_index
> and thus dev_pick_tx returns 65536 which is a bogus queue and
> can cause crash in dev_queue_xmit.
> 
> We fix this by only calling sk_tx_queue_get which does the proper
> checks.  The interface is that sk_tx_queue_get returns the TX queue
> if the sock argument is non-NULL and TX queue is recorded, else it
> returns -1.  sk_tx_queue_recorded is no longer used so it can be
> completely removed.
> 
> Signed-off-by: Tom Herbert <therbert@google.com>

Applied, thanks Tom!