tree 84ac1b5a0f65276f68bae561519e6568507e58d4
parent b4e467c82f8c12af78b6f6fa5730cb7dea7af1b4
author Willem de Bruijn <willemb@google.com> 1557941356 -0400
committer David S. Miller <davem@davemloft.net> 1558034270 -0700

net: test nouarg before dereferencing zerocopy pointers

Zerocopy skbs without completion notification were added for packet
sockets with PACKET_TX_RING user buffers. Those signal completion
through the TP_STATUS_USER bit in the ring. Zerocopy annotation was
added only to avoid premature notification after clone or orphan, by
triggering a copy on these paths for these packets.

The mechanism had to define a special "no-uarg" mode because packet
sockets already use skb_uarg(skb) == skb_shinfo(skb)->destructor_arg
for a different pointer.

Before deferencing skb_uarg(skb), verify that it is a real pointer.

Fixes: 5cd8d46ea1562 ("packet: copy user buffers before orphan or clone")
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>