On 01/21/15 at 08:14pm, Herbert Xu wrote:

On Wed, Jan 21, 2015 at 04:15:55PM +1100, Herbert Xu wrote:

quoted

I failed to address the security aspect of this approach.  Obviously
this can only work if the only entites doing the walk are trusted.
Which means that the vast majority (if not all) hash table users
would be excluded, in particular, netlink.

OK maybe we can get around this.  So we will postpone the resize
or rehash when a walk is in place, however, when we hit a hard
limit, i.e., when insert would otherwise fail, then we do the
rehash regardless of any outstanding walks.  The walks will just
behave erratically or we could force them to start from scratch
again.

Exactly. I think we also need a timer to abort walks because if
only a single walker is allowed, an attacker could start a walk and
not complete it to block out everybody else.