Re: [PATCH 3/3] usercopy: Add find_vmap_area_try() to avoid deadlocks

Kees Cook
2022-09-16T15:09:21Z

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.

Thanks!

-Kees

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Kees Cook