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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Tue, 11 Jan 2022 11:34:53 -0800
Message-ID: <CAHk-=wj9-9mFcoaD3rdHd+HKYpyTXkkE2iJkPoTTCrp-+sD=ew@mail.gmail.com>
Subject: Re: [PATCH v2 1/1] psi: Fix uaf issue when psi trigger is destroyed
 while being polled
To:     Suren Baghdasaryan <surenb@google.com>
Cc:     Eric Biggers <ebiggers@kernel.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Tejun Heo <tj@kernel.org>, Zefan Li <lizefan.x@bytedance.com>,
        Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Juri Lelli <juri.lelli@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Jonathan Corbet <corbet@lwn.net>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Cgroups <cgroups@vger.kernel.org>,
        stable <stable@vger.kernel.org>,
        Android Kernel Team <kernel-team@android.com>,
        syzbot <syzbot+cdb5dd11c97cc532efad@syzkaller.appspotmail.com>
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On Tue, Jan 11, 2022 at 11:27 AM Suren Baghdasaryan <surenb@google.com> wrote:
>
> Thanks for the explanation!
> So, it sounds like the best (semantically correct) option I have here
> is smp_store_release() to set the pointer, and then smp_load_acquire()
> to read it. Is my understanding correct?

Yeah, that's the clearest one from a memory ordering standpoint, and
is generally also cheap.

                Linus