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uprobes: __replace_page() should not use page_address_in_vma()
page_address_in_vma(old_page) in __replace_page() is ugly and wrong. The caller already knows the correct virtual address, this page was found by get_user_pages(vaddr). However, page_address_in_vma() can actually fail if page->mapping was cleared by __delete_from_page_cache() after get_user_pages() returns. But this means the race with page reclaim, write_opcode() should not fail, it should retry and read this page again. Probably the race with remove_mapping() is not possible due to page_freeze_refs() logic, but afaics at least shmem_writepage()->shmem_delete_from_page_cache() can clear ->mapping. We could change __replace_page() to return -EAGAIN in this case, but it would be better to simply use the caller's vaddr and rely on page_check_address(). Signed-off-by: Oleg Nesterov <[email protected]> Acked-by: Srikar Dronamraju <srikar.vnet.ibm.com> Cc: Anton Arapov <[email protected]> Cc: Srikar Dronamraju <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]>
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