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Git commit 3610cce87af0693603db171d5b6f6735f5e3dc5b (yeah my own :-/) introduced a bug in regard to pud/pmd table entries. If the address of the page table refered to by a pud/pmd value happens to have zeroes in the lower 32 bits, pud_present and pmd_present return false. The obvious effect is that this triggers the BUG_ON in exit_mmap because some ptes will not get released on process end. Worse is that the next fault for memory covered by that pud/pmd will allocate another pmd/pte table and populate the pud/pmd entry. The old page table entries hanging below this entry are lost! The fix is simple, properly check against 0. The check is added for pud_none/pmd_none as well even if these two functions work because the invalid bit is in the lower 32 bits. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>