Re: [patch 3/4 -mm] flex_array: poison free elements

From: Dave Hansen
Date: Mon Aug 24 2009 - 17:17:21 EST

On Mon, 2009-08-24 at 13:41 -0700, David Rientjes wrote:
> LEX_ARRAY_FREE (or an additional poison value to
> distinguish between use-uninitialized vs. use-after-free) must be used in
> flex_array_clear() otherwise the cgroup patchset, the only proposed user
> of this library code, could never shrink this array when pid's are free
> like the kmalloc vs. vmalloc patchset could do.

Are you saying that you expected it to never reallocate the array, but
have a permanent flex_array and that it just calls flex_array_clear() on
the elements that it doesn't want any more, and the array ends up
sparsely populated? I can see why we'd need a poison value in that

Or, are we just talking about a situation where we need to truncate the

-- Dave

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