On 05/09/2018 12:21 PM, Willem de Bruijn wrote:
> Indeed. The skb shared info struct is zeroed by dev_validate_header > as a result of dev->hard_header_len exceeding skb->end - skb->data. > > Not exactly sure yet how this can happen. The hard header length space > is accounted for during allocation as reserved memory. But, > packet_alloc_skb does call skb_reserve(), moving skb->data > effectively beyond this reserved region. > > It may be incorrect to pass skb->data to dev_validate_header, as that > does not point to the start of the ll_header anymore. Still figuring out what > the right fix is.. > I believe the bug happens if the sock_wmalloc() call at line 1921 has to sleep. device can change (or at lest dev->hard_header_len can change) So we need to bailout if reserved/hhlen had changed. Or revert some patches, since dev_hold() and dev_put() are no longer high cost, since it is now using per cpu counter.
