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Date: Wed, 26 Jul 2017 11:55:44 -0500 (CDT)
From: Christopher Lameter <cl@linux.com>
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To: Kees Cook <keescook@chromium.org>
cc: Alexander Popov <alex.popov@linux.com>,
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Subject: Re: [v3] mm: Add SLUB free list pointer obfuscation
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On Wed, 26 Jul 2017, Kees Cook wrote:

> >> What happens if, instead of BUG_ON, we do:
> >>
> >> if (unlikely(WARN_RATELIMIT(object == fp, "double-free detected"))
> >>         return;
> >
> > This may work for the free fastpath but the set_freepointer function is
> > use in multiple other locations. Maybe just add this to the fastpath
> > instead of to this fucnction?
>
> Do you mean do_slab_free()?

Yes inserting these lines into do_slab_free() would simple ignore the
double free operation in the fast path and that would be safe.

Although in either case we are adding code to the fastpath...