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Date:   Wed, 12 Jan 2022 12:06:04 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Eric Biggers <ebiggers@kernel.org>,
        Suren Baghdasaryan <surenb@google.com>,
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Subject: Re: [PATCH v2 1/1] psi: Fix uaf issue when psi trigger is destroyed
 while being polled
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On Tue, Jan 11, 2022 at 11:11:32AM -0800, Linus Torvalds wrote:

> Of course, in practice, for pointers, the whole "dereference off a
> pointer" on the read side *does* imply a barrier in all relevant
> situations. So yes, a smp_store_release() -> READ_ONCE() does work in
> practice, although it's technically wrong (in particular, it's wrong
> on alpha, because of the completely broken memory ordering that alpha
> has that doesn't even honor data dependencies as read-side orderings)

On a tangent, that actually works, even on Alpha, see commit
d646285885154 ("alpha: Override READ_ONCE() with barriered
implementation").