Re: [PATCH] proc: Disable /proc/$pid/wchan

[Mark Brown]

On Wed, Sep 29, 2021 at 11:54:55AM -0700, Kees Cook wrote:
> On Mon, Sep 27, 2021 at 01:50:56PM -0700, Josh Poimboeuf wrote:

> > Even with that patch, it doesn't lock the task's runqueue before reading
> > the stack, so there's still the possibility of the task running on
> > another CPU and the unwinder going off the rails a bit, which might be
> > used by an attacker in creative ways similar to the /proc/<pid>/stack
> > vulnerability Jann mentioned earlier.

> Since I think we're considering get_wchan() to be slow-path, can we just
> lock the runqueue and use arch_stack_walk_reliable()?

Unfortunately arch_stack_walk_reliable() is only available for powerpc,
s390 and x86 currently - work is in progress to implement it for arm64
as well but it's not there yet.

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