On Tue, 2016-08-30 at 07:57 -0400, Jamal Hadi Salim wrote:

        if (flags & SKBMOD_F_SWAPMAC) {
                u8 tmpaddr[ETH_ALEN];
                /*XXX: I am sure we can come up with something more efficient */
                ether_addr_copy(tmpaddr, eth_hdr(skb)->h_dest);
                ether_addr_copy(eth_hdr(skb)->h_dest, eth_hdr(skb)->h_source);
                ether_addr_copy(eth_hdr(skb)->h_source, tmpaddr);
        }

While ether_addr_copy() is accepting u8 pointers, data must be aligned to u16 at least.

(See comments in include/linux/etherdevice.h)

Some arches/compilers might do things here that would generate a trap
if tmpaddr is not aligned.