On Tue, Sep 1, 2015 at 12:55 PM, Tom Herbert <t...@herbertland.com> wrote: > On Tue, Sep 1, 2015 at 12:20 PM, Pravin Shelar <pshe...@nicira.com> wrote: >> On Tue, Sep 1, 2015 at 7:19 AM, Tom Herbert <t...@herbertland.com> wrote: >>> On Mon, Aug 31, 2015 at 10:15 PM, Pravin Shelar <pshe...@nicira.com> wrote: >>>> On Mon, Aug 31, 2015 at 9:12 PM, Tom Herbert <t...@herbertland.com> wrote: >>>>> On Mon, Aug 31, 2015 at 3:55 PM, Pravin B Shelar <pshe...@nicira.com> >>>>> wrote: >>>>>> VXLAN device can receive skb with checksum partial. But the checksum >>>>>> offset could be in outer header which is pulled on receive. Such skb >>>>>> can cause the panic when checksum is calculated on skb. Following patch >>>>>> fixes the bug by setting checksum unnecessary while pulling outer header. >>>>>> >>>>> Okay, I think I understand what you are doing. I suggest in the >>>>> openvswitch path, if there is a checksum CHECKSUM_PARTIAL that refers >>>>> to the outer headers which must have been verified at this point then >>>>> set to CHECKSUM_NONE-- assuming CHECKSUM_UNNECESSARY on the inner >>>>> header is not correct in this case. If the CHECKSUM_PARTIAL refers to >>>>> the inner header then you can call skb_checksum_help to resolve an >>>>> inner checksum. >>>>> >>>> >>>> That would be OVS specific fix, But I do see skb_checksum_help() >>>> called in multiple places outside OVS that could result in similar >>>> kernel panic. Therefore I want to solve it up in networking stack >>>> rather than in OVS. >>>> >>> Please try to reproduce this out of OVS from the top of the tree then >>> and report down exactly where panic is occurring the code. Unlike most >>> of the of the other cases where skb_checksum_help() is being called >>> this in the RX path so skb is probably not pulled over the checksum >>> offset for those. Even so, if the skb is pulled beyond the checksum >>> offset then this should result in a negative offset in >>> skb_checksum_start_offset(skb) which should be okay. It looks like >>> this in itself should not be causing your panic. >>> >> >> ip_do_fragment() also calls skb_checksum_help() that can results in >> similar panic. But it is not easy to reproduce it in this case due to >> call site is in exception path. >> The negative checksum offset can atleast cause assert failure in >> skb_checksum_help(). I will send patch to fix that. > > Which BUG_ON do you see is hitting?
BUG_ON(offset >= skb_headlen(skb)); where skb_headlen() returns unsigned int, therefore negative offset cast to unsigned int. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
