From: Eyal Birger eyal.birger@gmail.com
[ Upstream commit d549699048b4b5c22dd710455bcdb76966e55aa3 ]
In the patchset merged by commit b9fcf0a0d826 ("Merge branch 'support-AF_PACKET-for-layer-3-devices'") L3 devices which did not have header_ops were given one for the purpose of protocol parsing on af_packet transmit path.
That change made af_packet receive path regard these devices as having a visible L3 header and therefore aligned incoming skb->data to point to the skb's mac_header. Some devices, such as ipip, xfrmi, and others, do not reset their mac_header prior to ingress and therefore their incoming packets became malformed.
Ideally these devices would reset their mac headers, or af_packet would be able to rely on dev->hard_header_len being 0 for such cases, but it seems this is not the case.
Fix by changing af_packet RX ll visibility criteria to include the existence of a '.create()' header operation, which is used when creating a device hard header - via dev_hard_header() - by upper layers, and does not exist in these L3 devices.
As this predicate may be useful in other situations, add it as a common dev_has_header() helper in netdevice.h.
Fixes: b9fcf0a0d826 ("Merge branch 'support-AF_PACKET-for-layer-3-devices'") Signed-off-by: Eyal Birger eyal.birger@gmail.com Acked-by: Jason A. Donenfeld Jason@zx2c4.com Acked-by: Willem de Bruijn willemb@google.com Link: https://lore.kernel.org/r/20201121062817.3178900-1-eyal.birger@gmail.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/linux/netdevice.h | 5 +++++ net/packet/af_packet.c | 38 +++++++++++++++++++++----------------- 2 files changed, 26 insertions(+), 17 deletions(-)
--- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -3103,6 +3103,11 @@ static inline bool dev_validate_header(c return false; }
+static inline bool dev_has_header(const struct net_device *dev) +{ + return dev->header_ops && dev->header_ops->create; +} + typedef int gifconf_func_t(struct net_device * dev, char __user * bufptr, int len, int size); int register_gifconf(unsigned int family, gifconf_func_t *gifconf); --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -93,38 +93,42 @@
/* Assumptions: - - if device has no dev->hard_header routine, it adds and removes ll header - inside itself. In this case ll header is invisible outside of device, - but higher levels still should reserve dev->hard_header_len. - Some devices are enough clever to reallocate skb, when header - will not fit to reserved space (tunnel), another ones are silly - (PPP). + - If the device has no dev->header_ops->create, there is no LL header + visible above the device. In this case, its hard_header_len should be 0. + The device may prepend its own header internally. In this case, its + needed_headroom should be set to the space needed for it to add its + internal header. + For example, a WiFi driver pretending to be an Ethernet driver should + set its hard_header_len to be the Ethernet header length, and set its + needed_headroom to be (the real WiFi header length - the fake Ethernet + header length). - packet socket receives packets with pulled ll header, so that SOCK_RAW should push it back.
On receive: -----------
-Incoming, dev->hard_header!=NULL +Incoming, dev_has_header(dev) == true mac_header -> ll header data -> data
-Outgoing, dev->hard_header!=NULL +Outgoing, dev_has_header(dev) == true mac_header -> ll header data -> ll header
-Incoming, dev->hard_header==NULL - mac_header -> UNKNOWN position. It is very likely, that it points to ll - header. PPP makes it, that is wrong, because introduce - assymetry between rx and tx paths. +Incoming, dev_has_header(dev) == false + mac_header -> data + However drivers often make it point to the ll header. + This is incorrect because the ll header should be invisible to us. data -> data
-Outgoing, dev->hard_header==NULL - mac_header -> data. ll header is still not built! +Outgoing, dev_has_header(dev) == false + mac_header -> data. ll header is invisible to us. data -> data
Resume - If dev->hard_header==NULL we are unlikely to restore sensible ll header. + If dev_has_header(dev) == false we are unable to restore the ll header, + because it is invisible to us.
On transmit: @@ -2066,7 +2070,7 @@ static int packet_rcv(struct sk_buff *sk
skb->dev = dev;
- if (dev->header_ops) { + if (dev_has_header(dev)) { /* The device has an explicit notion of ll header, * exported to higher levels. * @@ -2195,7 +2199,7 @@ static int tpacket_rcv(struct sk_buff *s if (!net_eq(dev_net(dev), sock_net(sk))) goto drop;
- if (dev->header_ops) { + if (dev_has_header(dev)) { if (sk->sk_type != SOCK_DGRAM) skb_push(skb, skb->data - skb_mac_header(skb)); else if (skb->pkt_type == PACKET_OUTGOING) {