net: hold sock reference while processing tx timestamps
authorRichard Cochran <richardcochran@gmail.com>
Fri, 21 Oct 2011 00:49:15 +0000 (00:49 +0000)
committerGreg Kroah-Hartman <gregkh@suse.de>
Fri, 11 Nov 2011 17:43:08 +0000 (09:43 -0800)
commit6d06e8d0a5bcc13717291fe46303bfd32cfb9d7a
treee7a2f64d9e1a609789253b1488842ce29ab9c514
parentf9aea842ccd9be4c49e90c848afd187dd9880638
net: hold sock reference while processing tx timestamps

commit da92b194cc36b5dc1fbd85206aeeffd80bee0c39 upstream.

The pair of functions,

 * skb_clone_tx_timestamp()
 * skb_complete_tx_timestamp()

were designed to allow timestamping in PHY devices. The first
function, called during the MAC driver's hard_xmit method, identifies
PTP protocol packets, clones them, and gives them to the PHY device
driver. The PHY driver may hold onto the packet and deliver it at a
later time using the second function, which adds the packet to the
socket's error queue.

As pointed out by Johannes, nothing prevents the socket from
disappearing while the cloned packet is sitting in the PHY driver
awaiting a timestamp. This patch fixes the issue by taking a reference
on the socket for each such packet. In addition, the comments
regarding the usage of these function are expanded to highlight the
rule that PHY drivers must use skb_complete_tx_timestamp() to release
the packet, in order to release the socket reference, too.

These functions first appeared in v2.6.36.

Reported-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Richard Cochran <richard.cochran@omicron.at>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Reviewed-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
include/linux/phy.h
include/linux/skbuff.h
net/core/timestamping.c