Re: use-after-free in sock_wake_async

[Eric Dumazet]

On Thu, 2015-11-26 at 18:03 +0100, Hannes Frederic Sowa wrote:

> Also isn't the reason why slub exists so it can track memory regions
> per-cpu.

call_rcu() and kfree_rcu() will add a grace period (multiple ms) where
the cpu will likely evict from its caches the data contained in the
'about to be freed' objects, defeating the SLUB/SLAB ability to quickly
reuse a freed and hot object (LIFO)

This is one of the major RCU drawback : Force a FIFO behavior in object
reuse while LIFO one is much better for data locality, especially with
per-cpu lists.

Another problem is a slightly bigger working set size, which can hurt
some workloads that used to exactly fit cpu caches.


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