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.
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