When we receive a packet on a QMI device in raw IP mode, we should call
skb_reset_mac_header() to ensure that skb->mac_header contains a valid
offset in the packet. While it shouldn't really matter, the packets have
no MAC header and the interface is configured as-such, it seems certain
parts of the network stack expects a "good" value in skb->mac_header.
Without the skb_reset_mac_header() call added in this patch, for example
shaping traffic (using tc) triggers the following oops on the first
received packet:
[ 303.642957] skbuff: skb_under_panic: text:8f137918 len:177 put:67 head:8e4b0f00 data:8e4b0eff tail:0x8e4b0fb0 end:0x8e4b1520 dev:wwan0
[ 303.655045] Kernel bug detected[#1]:
[ 303.658622] CPU: 1 PID: 1002 Comm: logd Not tainted 4.9.58 #0
[ 303.664339] task: 8fdf05e0 task.stack: 8f15c000
[ 303.668844] $ 0 : 00000000 00000001 0000007a 00000000
[ 303.674062] $ 4 : 8149a2fc 8149a2fc 8149ce20 00000000
[ 303.679284] $ 8 : 00000030 3878303a 31623465 20303235
[ 303.684510] $12 : ded731e3 2626a277 00000000 03bd0000
[ 303.689747] $16 : 8ef62b40 00000043 8f137918 804db5fc
[ 303.694978] $20 : 00000001 00000004 8fc13800 00000003
[ 303.700215] $24 : 00000001 8024ab10
[ 303.705442] $28 : 8f15c000 8fc19cf0 00000043 802cc920
[ 303.710664] Hi : 00000000
[ 303.713533] Lo : 74e58000
[ 303.716436] epc : 802cc920 skb_panic+0x58/0x5c
[ 303.721046] ra : 802cc920 skb_panic+0x58/0x5c
[ 303.725639] Status: 11007c03 KERNEL EXL IE
[ 303.729823] Cause : 50800024 (ExcCode 09)
[ 303.733817] PrId : 0001992f (MIPS 1004Kc)
[ 303.737892] Modules linked in: rt2800pci rt2800mmio rt2800lib qcserial ppp_async option usb_wwan rt2x00pci rt2x00mmio rt2x00lib rndis_host qmi_wwan ppp_generic nf_nat_pptp nf_conntrack_pptp nf_conntrack_ipv6 mt76x2i
Process logd (pid: 1002, threadinfo=8f15c000, task=8fdf05e0, tls=77b3eee4)
[ 303.962509] Stack : 00000000 80408990 8f137918 000000b1 00000043 8e4b0f00 8e4b0eff 8e4b0fb0
[ 303.970871] 8e4b1520 8fec1800 00000043 802cd2a4 6e000045 00000043 00000000 8ef62000
[ 303.979219] 8eef5d00 8ef62b40 8fea7300 8f137918 00000000 00000000 0002bb01 793e5664
[ 303.987568] 8ef08884 00000001 8fea7300 00000002 8fc19e80 8eef5d00 00000006 00000003
[ 303.995934] 00000000 8030ba90 00000003 77ab3fd0 8149dc80 8004d1bc 8f15c000 8f383700
[ 304.004324] ...
[ 304.006767] Call Trace:
[ 304.009241] [<802cc920>] skb_panic+0x58/0x5c
[ 304.013504] [<802cd2a4>] skb_push+0x78/0x90
[ 304.017783] [<8f137918>] 0x8f137918
[ 304.021269] Code: 00602825 0c02a3b4 24842888 <000c000d> 8c870060 8c8200a0 0007382b 00070336 8c88005c
[ 304.031034]
[ 304.032805] ---[ end trace b778c482b3f0bda9 ]---
[ 304.041384] Kernel panic - not syncing: Fatal exception in interrupt
[ 304.051975] Rebooting in 3 seconds..
While the oops is for a 4.9-kernel, I was able to trigger the same oops with
net-next as of yesterday.
Signed-off-by: Kristian Evensen <kristian.evensen@xxxxxxxxx>
---
drivers/net/usb/qmi_wwan.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/net/usb/qmi_wwan.c b/drivers/net/usb/qmi_wwan.c
index db7279d5b250..5b22645c7c8c 100644
--- a/drivers/net/usb/qmi_wwan.c
+++ b/drivers/net/usb/qmi_wwan.c
@@ -499,6 +499,7 @@ static int qmi_wwan_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
return 1;
}
if (rawip) {
+ skb_reset_mac_header(skb);
skb->dev = dev->net; /* normally set by eth_type_trans */
skb->protocol = proto;
return 1;
--
2.11.0
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