linux-kernel - Re: [PATCH 2/3] userfaultfd: UFFDIO

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Message-ID: <CAG48ez1kBzoeYAvXVneuQqU_0zXKWV7UZGef=WnyNc32vNQLhg@mail.gmail.com>
Date:   Thu, 21 Sep 2023 18:59:39 +0200
From:   Jann Horn <jannh@...gle.com>
To:     Suren Baghdasaryan <surenb@...gle.com>
Cc:     akpm@...ux-foundation.org, viro@...iv.linux.org.uk,
        brauner@...nel.org, shuah@...nel.org, aarcange@...hat.com,
        lokeshgidra@...gle.com, peterx@...hat.com, david@...hat.com,
        hughd@...gle.com, mhocko@...e.com, axelrasmussen@...gle.com,
        rppt@...nel.org, willy@...radead.org, Liam.Howlett@...cle.com,
        zhangpeng362@...wei.com, bgeffon@...gle.com,
        kaleshsingh@...gle.com, ngeoffray@...gle.com, jdduke@...gle.com,
        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        kernel-team@...roid.com
Subject: Re: [PATCH 2/3] userfaultfd: UFFDIO_REMAP uABI

On Thu, Sep 14, 2023 at 9:28 PM Jann Horn <jannh@...gle.com> wrote:
> Though, uuuuuh, I guess if that's true, the existing
> vma_is_anonymous() is broken, since that also just checks ->vm_ops?
> I'm not sure what the consequences of that would be... Either way,
> vma_is_anonymous() might be the better way to check for anonymous VMAs
> here, and someone should figure out whether vma_is_anonymous() needs
> to be fixed.

(Not really relevant to the rest of the thread, but just as a
sidenote: Turns out this is not an issue; since commit bfd40eaff5ab
("mm: fix vma_is_anonymous() false-positives"), VMAs where the ->mmap
handler does not set an operations pointer end up with a dummy
operations pointer.)