> On 2 Jul 2018, at 19:39, Dave Taht <dave.taht@gmail.com> wrote:
> 
>> 
> 
> This seems like it will introduce problems with stuff that isn't or is
> legitimately broken in the first place, pointing to potentially random
> data in the wrong place.
> 
> would a workaround be adding more padding to the cake stats output so
> it's always even?
> 
> why does it work as written on arm?

If I understand correctly:  This will only be a problem on architectures that require alignment of 64 bit values to 8 byte boundaries which is achieved by padding the structure by a dummy (4 byte) value if required.  So to hit this bug we need kernel symbol CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS undefined *and* we need a netlink stats structure that needs a 4 byte dummy pad value to align to 8 bytes.  Of the architectures tested, MIPS is the only one that DOES NOT set CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS and thus may be exposed to the bug.

arm sets CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS and thus no padding is ever required/added, thus pointers always point to the correct data location.