From: Xie He xie.he.0141@gmail.com
[ Upstream commit c7ca03c216acb14466a713fedf1b9f2c24994ef2 ]
1. Added a skb->len check
This driver expects upper layers to include a pseudo header of 1 byte when passing down a skb for transmission. This driver will read this 1-byte header. This patch added a skb->len check before reading the header to make sure the header exists.
2. Changed to use needed_headroom instead of hard_header_len to request necessary headroom to be allocated
In net/packet/af_packet.c, the function packet_snd first reserves a headroom of length (dev->hard_header_len + dev->needed_headroom). Then if the socket is a SOCK_DGRAM socket, it calls dev_hard_header, which calls dev->header_ops->create, to create the link layer header. If the socket is a SOCK_RAW socket, it "un-reserves" a headroom of length (dev->hard_header_len), and assumes the user to provide the appropriate link layer header.
So according to the logic of af_packet.c, dev->hard_header_len should be the length of the header that would be created by dev->header_ops->create.
However, this driver doesn't provide dev->header_ops, so logically dev->hard_header_len should be 0.
So we should use dev->needed_headroom instead of dev->hard_header_len to request necessary headroom to be allocated.
This change fixes kernel panic when this driver is used with AF_PACKET SOCK_RAW sockets.
Call stack when panic:
[ 168.399197] skbuff: skb_under_panic: text:ffffffff819d95fb len:20 put:14 head:ffff8882704c0a00 data:ffff8882704c09fd tail:0x11 end:0xc0 dev:veth0 ... [ 168.399255] Call Trace: [ 168.399259] skb_push.cold+0x14/0x24 [ 168.399262] eth_header+0x2b/0xc0 [ 168.399267] lapbeth_data_transmit+0x9a/0xb0 [lapbether] [ 168.399275] lapb_data_transmit+0x22/0x2c [lapb] [ 168.399277] lapb_transmit_buffer+0x71/0xb0 [lapb] [ 168.399279] lapb_kick+0xe3/0x1c0 [lapb] [ 168.399281] lapb_data_request+0x76/0xc0 [lapb] [ 168.399283] lapbeth_xmit+0x56/0x90 [lapbether] [ 168.399286] dev_hard_start_xmit+0x91/0x1f0 [ 168.399289] ? irq_init_percpu_irqstack+0xc0/0x100 [ 168.399291] __dev_queue_xmit+0x721/0x8e0 [ 168.399295] ? packet_parse_headers.isra.0+0xd2/0x110 [ 168.399297] dev_queue_xmit+0x10/0x20 [ 168.399298] packet_sendmsg+0xbf0/0x19b0 ......
Cc: Willem de Bruijn willemdebruijn.kernel@gmail.com Cc: Martin Schiller ms@dev.tdt.de Cc: Brian Norris briannorris@chromium.org Signed-off-by: Xie He xie.he.0141@gmail.com Acked-by: Willem de Bruijn willemb@google.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/wan/lapbether.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
--- a/drivers/net/wan/lapbether.c +++ b/drivers/net/wan/lapbether.c @@ -160,6 +160,12 @@ static netdev_tx_t lapbeth_xmit(struct s if (!netif_running(dev)) goto drop;
+ /* There should be a pseudo header of 1 byte added by upper layers. + * Check to make sure it is there before reading it. + */ + if (skb->len < 1) + goto drop; + switch (skb->data[0]) { case X25_IFACE_DATA: break; @@ -308,6 +314,7 @@ static void lapbeth_setup(struct net_dev dev->netdev_ops = &lapbeth_netdev_ops; dev->needs_free_netdev = true; dev->type = ARPHRD_X25; + dev->hard_header_len = 0; dev->mtu = 1000; dev->addr_len = 0; } @@ -334,7 +341,8 @@ static int lapbeth_new_device(struct net * then this driver prepends a length field of 2 bytes, * then the underlying Ethernet device prepends its own header. */ - ndev->hard_header_len = -1 + 3 + 2 + dev->hard_header_len; + ndev->needed_headroom = -1 + 3 + 2 + dev->hard_header_len + + dev->needed_headroom;
lapbeth = netdev_priv(ndev); lapbeth->axdev = ndev;