From b30fe6c7ced70f62862c3d09357e7e8084e98d9f Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" Date: Wed, 11 Feb 2015 15:26:53 -0800 Subject: mm: fix false-positive warning on exit due mm_nr_pmds(mm) The problem is that we check nr_ptes/nr_pmds in exit_mmap() which happens *before* pgd_free(). And if an arch does pte/pmd allocation in pgd_alloc() and frees them in pgd_free() we see offset in counters by the time of the checks. We tried to workaround this by offsetting expected counter value according to FIRST_USER_ADDRESS for both nr_pte and nr_pmd in exit_mmap(). But it doesn't work in some cases: 1. ARM with LPAE enabled also has non-zero USER_PGTABLES_CEILING, but upper addresses occupied with huge pmd entries, so the trick with offsetting expected counter value will get really ugly: we will have to apply it nr_pmds, but not nr_ptes. 2. Metag has non-zero FIRST_USER_ADDRESS, but doesn't do allocation pte/pmd page tables allocation in pgd_alloc(), just setup a pgd entry which is allocated at boot and shared accross all processes. The proposal is to move the check to check_mm() which happens *after* pgd_free() and do proper accounting during pgd_alloc() and pgd_free() which would bring counters to zero if nothing leaked. Signed-off-by: Kirill A. Shutemov Reported-by: Tyler Baker Tested-by: Tyler Baker Tested-by: Nishanth Menon Cc: Russell King Cc: James Hogan Cc: Guan Xuetao Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/unicore32/mm/pgd.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'arch/unicore32') diff --git a/arch/unicore32/mm/pgd.c b/arch/unicore32/mm/pgd.c index 08b8d42..2ade20d 100644 --- a/arch/unicore32/mm/pgd.c +++ b/arch/unicore32/mm/pgd.c @@ -69,6 +69,7 @@ pgd_t *get_pgd_slow(struct mm_struct *mm) no_pte: pmd_free(mm, new_pmd); + mm_dec_nr_pmds(mm); no_pmd: free_pages((unsigned long)new_pgd, 0); no_pgd: @@ -96,7 +97,9 @@ void free_pgd_slow(struct mm_struct *mm, pgd_t *pgd) pte = pmd_pgtable(*pmd); pmd_clear(pmd); pte_free(mm, pte); + atomic_long_dec(&mm->nr_ptes); pmd_free(mm, pmd); + mm_dec_nr_pmds(mm); free: free_pages((unsigned long) pgd, 0); } -- cgit v1.1