linux-kernel - Re: [PATCH] mm/userfaultfd: fix memory corruption due to writeprotect

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Message-ID: <X+TpAAuGm7KSLr8G@redhat.com>
Date:   Thu, 24 Dec 2020 14:16:16 -0500
From:   Andrea Arcangeli <aarcange@...hat.com>
To:     Nadav Amit <nadav.amit@...il.com>
Cc:     Yu Zhao <yuzhao@...gle.com>, Andy Lutomirski <luto@...capital.net>,
        Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Xu <peterx@...hat.com>, linux-mm <linux-mm@...ck.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Pavel Emelyanov <xemul@...nvz.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        stable <stable@...r.kernel.org>,
        Minchan Kim <minchan@...nel.org>,
        Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] mm/userfaultfd: fix memory corruption due to writeprotect

On Thu, Dec 24, 2020 at 01:49:45PM -0500, Andrea Arcangeli wrote:
> Without the above, can't the CPU decrement the tlb_flush_pending while
> the IPI to ack didn't arrive yet in csd_lock_wait?

Ehm: csd_lock_wait has smp_acquire__after_ctrl_dep() so the write side
looks ok after all sorry.