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    SubjectRe: [PATCH 9/9] mm: introduce VM_POPULATE flag to better deal with racy userspace programs
    On 12/20/2012 07:49 PM, Michel Lespinasse wrote:
    > The vm_populate() code populates user mappings without constantly
    > holding the mmap_sem. This makes it susceptible to racy userspace
    > programs: the user mappings may change while vm_populate() is running,
    > and in this case vm_populate() may end up populating the new mapping
    > instead of the old one.
    >
    > In order to reduce the possibility of userspace getting surprised by
    > this behavior, this change introduces the VM_POPULATE vma flag which
    > gets set on vmas we want vm_populate() to work on. This way
    > vm_populate() may still end up populating the new mapping after such a
    > race, but only if the new mapping is also one that the user has
    > requested (using MAP_SHARED, MAP_LOCKED or mlock) to be populated.
    >
    > Signed-off-by: Michel Lespinasse <walken@google.com>

    Acked-by: Rik van Riel <ri

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