aio: fix race in ring buffer page lookup introduced by page migration support
Prior to the introduction of page migration support in "fs/aio: Add support
to aio ring pages migration" / 36bc08cc01709b4a9bb563b35aa530241ddc63e3,
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: Benjamin LaHaise <bcrl@kvack.org>
1 file changed