On Fri, Oct 26, 2018 at 03:17:07AM -0700, Matthew Wilcox wrote:

On Fri, Oct 26, 2018 at 11:32:05AM +0200, Peter Zijlstra wrote:

quoted

On Wed, Oct 24, 2018 at 12:35:00AM +0300, Igor Stoppa wrote:

quoted

Some of the data structures used in list management are composed by two
pointers. Since the kernel is now configured by default to randomize the
layout of data structures soleley composed by pointers, this might
prevent correct type punning between these structures and their write
rare counterpart.

'might' doesn't really work for me. Either it does or it does not.

He means "Depending on the random number generator, the two pointers
might be AB or BA.  If they're of opposite polarity (50% of the time),
it _will_ break, and 50% of the time it _won't_ break."

So don't do that then. If he were to include struct list_head inside his
prlist_head, then there is only the one randomization and things will
just work.

Also, I really don't see why he needs that second type and all that type
punning crap in the first place.