From 6dec97dc92946eb479e6ebb54a61f8226cceefec Mon Sep 17 00:00:00 2001 From: Cyrill Gorcunov Date: Tue, 27 Aug 2013 12:37:18 +0400 Subject: [PATCH] mm: move_ptes -- Set soft dirty bit depending on pte type Dave reported corrupted swap entries | [ 4588.541886] swap_free: Unused swap offset entry 00002d15 | [ 4588.541952] BUG: Bad page map in process trinity-kid12 pte:005a2a80 pmd:22c01f067 and Hugh pointed that in move_ptes _PAGE_SOFT_DIRTY bit set regardless the type of entry pte consists of. The trick here is that when we carry soft dirty status in swap entries we are to use _PAGE_SWP_SOFT_DIRTY instead, because this is the only place in pte which can be used for own needs without intersecting with bits owned by swap entry type/offset. Reported-and-tested-by: Dave Jones Signed-off-by: Cyrill Gorcunov Cc: Pavel Emelyanov Analyzed-by: Hugh Dickins Cc: Hillf Danton Cc: Andrew Morton Signed-off-by: Linus Torvalds --- mm/mremap.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/mm/mremap.c b/mm/mremap.c index 457d34e..0843feb 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -15,6 +15,7 @@ #include #include #include +#include #include #include #include @@ -69,6 +70,23 @@ static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma, return pmd; } +static pte_t move_soft_dirty_pte(pte_t pte) +{ + /* + * Set soft dirty bit so we can notice + * in userspace the ptes were moved. + */ +#ifdef CONFIG_MEM_SOFT_DIRTY + if (pte_present(pte)) + pte = pte_mksoft_dirty(pte); + else if (is_swap_pte(pte)) + pte = pte_swp_mksoft_dirty(pte); + else if (pte_file(pte)) + pte = pte_file_mksoft_dirty(pte); +#endif + return pte; +} + static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd, unsigned long old_addr, unsigned long old_end, struct vm_area_struct *new_vma, pmd_t *new_pmd, @@ -126,7 +144,8 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd, continue; pte = ptep_get_and_clear(mm, old_addr, old_pte); pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr); - set_pte_at(mm, new_addr, new_pte, pte_mksoft_dirty(pte)); + pte = move_soft_dirty_pte(pte); + set_pte_at(mm, new_addr, new_pte, pte); } arch_leave_lazy_mmu_mode(); -- 2.7.4