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    aio: fix race in ring buffer page lookup introduced by page migration support · d6c355c7
    Benjamin LaHaise 提交于
    Prior to the introduction of page migration support in "fs/aio: Add support
    to aio ring pages migration" / 36bc08cc,
    mapping of the ring buffer pages was done via get_user_pages() while
    retaining mmap_sem held for write.  This avoided possible races with userland
    racing an munmap() or mremap().  The page migration patch, however, switched
    to using mm_populate() to prime the page mapping.  mm_populate() cannot be
    called with mmap_sem held.
    
    Instead of dropping the mmap_sem, revert to the old behaviour and simply
    drop the use of mm_populate() since get_user_pages() will cause the pages to
    get mapped anyways.  Thanks to Al Viro for spotting this issue.
    Signed-off-by: NBenjamin LaHaise <bcrl@kvack.org>
    d6c355c7
aio.c 36.6 KB