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Date:   Fri, 16 Sep 2022 08:09:16 -0700
From:   Kees Cook <>
To:     Matthew Wilcox <>
Cc:     Uladzislau Rezki <>,
        Andrew Morton <>,
        Yu Zhao <>,,,,
        Peter Zijlstra <>,
        Ingo Molnar <>,,,,
Subject: Re: [PATCH 3/3] usercopy: Add find_vmap_area_try() to avoid deadlocks

On Fri, Sep 16, 2022 at 03:46:07PM +0100, Matthew Wilcox wrote:
> On Fri, Sep 16, 2022 at 06:59:57AM -0700, Kees Cook wrote:
> > The check_object_size() checks under CONFIG_HARDENED_USERCOPY need to be
> > more defensive against running from interrupt context. Use a best-effort
> > check for VMAP areas when running in interrupt context
> I had something more like this in mind:

Yeah, I like -EAGAIN. I'd like to keep the interrupt test to choose lock
vs trylock, otherwise it's trivial to bypass the hardening test by having
all the other CPUs beating on the spinlock.



Kees Cook

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