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    SubjectRe: [PATCH v3 1/4] mm/mlock: return EINVAL if len overflows for mlock/munlock
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    On 06.02.23 01:48, mawupeng wrote:
    >
    >
    > On 2023/2/4 1:14, David Hildenbrand wrote:
    >> On 28.01.23 07:32, Wupeng Ma wrote:
    >>> From: Ma Wupeng <mawupeng1@huawei.com>
    >>>
    >>> While testing mlock, we have a problem if the len of mlock is ULONG_MAX.
    >>> The return value of mlock is zero. But nothing will be locked since the
    >>> len in do_mlock overflows to zero due to the following code in mlock:
    >>>
    >>>    len = PAGE_ALIGN(len + (offset_in_page(start)));
    >>>
    >>> The same problem happens in munlock.
    >>>
    >>> Add new check and return -EINVAL to fix this overflowing scenarios since
    >>> they are absolutely wrong.
    >>>
    >>> Return 0 early to avoid burn a bunch of cpu cycles if len == 0.
    >>>
    >>> Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>
    >>> ---
    >>>   mm/mlock.c | 14 ++++++++++++--
    >>>   1 file changed, 12 insertions(+), 2 deletions(-)
    >>>
    >>> diff --git a/mm/mlock.c b/mm/mlock.c
    >>> index 7032f6dd0ce1..eb09968ba27f 100644
    >>> --- a/mm/mlock.c
    >>> +++ b/mm/mlock.c
    >>> @@ -478,8 +478,6 @@ static int apply_vma_lock_flags(unsigned long start, size_t len,
    >>>       end = start + len;
    >>>       if (end < start)
    >>>           return -EINVAL;
    >>> -    if (end == start)
    >>> -        return 0;
    >>>       vma = mas_walk(&mas);
    >>>       if (!vma)
    >>>           return -ENOMEM;
    >>> @@ -575,7 +573,13 @@ static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t fla
    >>>       if (!can_do_mlock())
    >>>           return -EPERM;
    >>>   +    if (!len)
    >>> +        return 0;
    >>> +
    >>>       len = PAGE_ALIGN(len + (offset_in_page(start)));
    >>> +    if (!len)
    >>> +        return -EINVAL;
    >>> +
    >>>       start &= PAGE_MASK;
    >>
    >> The "ordinary" overflows are detected in apply_vma_lock_flags(), correct?
    >
    > Overflow is not checked anywhere however the ordinary return early if len == 0 is detected in apply_vma_lock_flags().
    >

    I meant the

    end = start + len;
    if (end < start)
    return -EINVAL;

    Essentially, what I wanted to double-check is that with your changes, we
    catch all kinds of overflows as documented in the man page, correct?

    --
    Thanks,

    David / dhildenb

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