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From:   Yu Zhao <yuzhao@google.com>
Date:   Thu, 10 Aug 2023 13:30:20 -0600
Message-ID: <CAOUHufbPN2Zh53-YOJo8r+sRuXMt4Oav1Py6wWJgGA3aWRNvfQ@mail.gmail.com>
Subject: Re: [PATCH mm-unstable fix] mm: userfaultfd: check for start + len
 overflow in validate_range: fix
To:     Axel Rasmussen <axelrasmussen@google.com>
Cc:     Alexander Viro <viro@zeniv.linux.org.uk>,
        Andrew Morton <akpm@linux-foundation.org>,
        Brian Geffon <bgeffon@google.com>,
        Christian Brauner <brauner@kernel.org>,
        David Hildenbrand <david@redhat.com>,
        Gaosheng Cui <cuigaosheng1@huawei.com>,
        Huang Ying <ying.huang@intel.com>,
        Hugh Dickins <hughd@google.com>,
        James Houghton <jthoughton@google.com>,
        Jiaqi Yan <jiaqiyan@google.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Kefeng Wang <wangkefeng.wang@huawei.com>,
        "Liam R. Howlett" <Liam.Howlett@oracle.com>,
        Miaohe Lin <linmiaohe@huawei.com>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        "Mike Rapoport (IBM)" <rppt@kernel.org>,
        Muchun Song <muchun.song@linux.dev>,
        Nadav Amit <namit@vmware.com>,
        Naoya Horiguchi <naoya.horiguchi@nec.com>,
        Peter Xu <peterx@redhat.com>,
        Ryan Roberts <ryan.roberts@arm.com>,
        Shuah Khan <shuah@kernel.org>,
        Steven Barrett <steven@liquorix.net>,
        Suleiman Souhlal <suleiman@google.com>,
        Suren Baghdasaryan <surenb@google.com>,
        "T.J. Alumbaugh" <talumbau@google.com>,
        ZhangPeng <zhangpeng362@huawei.com>, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-mm@kvack.org, linux-kselftest@vger.kernel.org
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On Thu, Aug 10, 2023 at 1:21=E2=80=AFPM Axel Rasmussen <axelrasmussen@googl=
e.com> wrote:
>
> A previous fixup to this commit fixed one issue, but introduced another:
> we're now overly strict when validating the src address for UFFDIO_COPY.
>
> Most of the validation in validate_range is useful to apply to src as
> well as dst, but page alignment is only a requirement for dst, not src.
> So, split the function up so src can use an "unaligned" variant, while
> still allowing us to share the majority of the code between the
> different cases.
>
> Reported-by: Ryan Roberts <ryan.roberts@arm.com>
> Closes: https://lore.kernel.org/linux-mm/8fbb5965-28f7-4e9a-ac04-1406ed8f=
c2d4@arm.com/T/#t
> Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>

Reviewed-by:  Yu Zhao <yuzhao@google.com>