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Re: [PATCH] usbnet: fix oops in usbnet_start_xmit [message #43994] Mon, 07 November 2011 14:05
Konstantin Khlebnikov is currently offline  Konstantin Khlebnikov
Messages: 2
Registered: November 2011
Junior Member
From: *parallels.com
Richard Cochran wrote:
> On Sun, Nov 06, 2011 at 10:33:37PM +0300, Konstantin Khlebnikov wrote:
>> This patch fixes the bug added in commit v3.1-rc7-1055-gf9b491e
>> SKB can be NULL at this point, at least for cdc-ncm.
>
> What? You mean .ndo_start_xmit is called with skb NULL?

no. cdc_ncm call usbnet_start_xmit with NULL skb from timer handler
and tx_fixup hook pickup skb from internal context. yeah, it really messy.

>
>> Let's call skb_tx_timestamp() after driver specific tx-fixup hacks.
>
> No, that won't work.
>
> That call is before the fixup on purpose, because some fixups add
> padding in front of the Ethernet payload, and this will spoil the PTP
> packet detection filter.
>
> I don't know why the skb can be NULL here. If that is really the case,
> then the correct fix is:
>
> if (skb)
> skb_tx_timestamp(skb);
>
> Thanks,
> Richard
>
>
>>
>> Signed-off-by: Konstantin Khlebnikov<khlebnikov@openvz.org>
>> ---
>> drivers/net/usb/usbnet.c | 4 ++--
>> 1 files changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
>> index 7d60821..485be70 100644
>> --- a/drivers/net/usb/usbnet.c
>> +++ b/drivers/net/usb/usbnet.c
>> @@ -1057,8 +1057,6 @@ netdev_tx_t usbnet_start_xmit (struct sk_buff *skb,
>> unsigned long flags;
>> int retval;
>>
>> - skb_tx_timestamp(skb);
>> -
>> // some devices want funky USB-level framing, for
>> // win32 driver (usually) and/or hardware quirks
>> if (info->tx_fixup) {
>> @@ -1075,6 +1073,8 @@ netdev_tx_t usbnet_start_xmit (struct sk_buff *skb,
>> }
>> length = skb->len;
>>
>> + skb_tx_timestamp(skb);
>> +
>> if (!(urb = usb_alloc_urb (0, GFP_ATOMIC))) {
>> netif_dbg(dev, tx_err, dev->net, "no urb\n");
>> goto drop;
>>
>> --
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