lkml.org 
[lkml]   [2020]   [Aug]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[net v3] drivers/net/wan/lapbether: Use needed_headroom instead of hard_header_len
Date
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
......

Additional change:
When sending, check skb->len to ensure the 1-byte pseudo header is
present before reading it.

Cc: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Cc: Brian Norris <briannorris@chromium.org>
Signed-off-by: Xie He <xie.he.0141@gmail.com>
---

Change from v2:
Added skb->len check when sending.

Change from v1:
None

---
drivers/net/wan/lapbether.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wan/lapbether.c b/drivers/net/wan/lapbether.c
index b2868433718f..8a3f7ba36f7e 100644
--- a/drivers/net/wan/lapbether.c
+++ b/drivers/net/wan/lapbether.c
@@ -157,6 +157,9 @@ static netdev_tx_t lapbeth_xmit(struct sk_buff *skb,
if (!netif_running(dev))
goto drop;

+ if (skb->len < 1)
+ goto drop;
+
switch (skb->data[0]) {
case X25_IFACE_DATA:
break;
@@ -305,6 +308,7 @@ static void lapbeth_setup(struct net_device *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;
}
@@ -331,7 +335,8 @@ static int lapbeth_new_device(struct net_device *dev)
* 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;
--
2.25.1
\
 
 \ /
  Last update: 2020-08-02 21:52    [W:0.072 / U:2.496 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site