From 0d665e7b109d512b7cae3ccef6e8654714887844 Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" Date: Fri, 19 Jan 2018 15:49:24 +0300 Subject: mm, page_vma_mapped: Drop faulty pointer arithmetics in check_pte() Tetsuo reported random crashes under memory pressure on 32-bit x86 system and tracked down to change that introduced page_vma_mapped_walk(). The root cause of the issue is the faulty pointer math in check_pte(). As ->pte may point to an arbitrary page we have to check that they are belong to the section before doing math. Otherwise it may lead to weird results. It wasn't noticed until now as mem_map[] is virtually contiguous on flatmem or vmemmap sparsemem. Pointer arithmetic just works against all 'struct page' pointers. But with classic sparsemem, it doesn't because each section memap is allocated separately and so consecutive pfns crossing two sections might have struct pages at completely unrelated addresses. Let's restructure code a bit and replace pointer arithmetic with operations on pfns. Signed-off-by: Kirill A. Shutemov Reported-and-tested-by: Tetsuo Handa Acked-by: Michal Hocko Fixes: ace71a19cec5 ("mm: introduce page_vma_mapped_walk()") Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds --- include/linux/swapops.h | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) (limited to 'include/linux/swapops.h') diff --git a/include/linux/swapops.h b/include/linux/swapops.h index 9c5a2628d6ce..1d3877c39a00 100644 --- a/include/linux/swapops.h +++ b/include/linux/swapops.h @@ -124,6 +124,11 @@ static inline bool is_write_device_private_entry(swp_entry_t entry) return unlikely(swp_type(entry) == SWP_DEVICE_WRITE); } +static inline unsigned long device_private_entry_to_pfn(swp_entry_t entry) +{ + return swp_offset(entry); +} + static inline struct page *device_private_entry_to_page(swp_entry_t entry) { return pfn_to_page(swp_offset(entry)); @@ -154,6 +159,11 @@ static inline bool is_write_device_private_entry(swp_entry_t entry) return false; } +static inline unsigned long device_private_entry_to_pfn(swp_entry_t entry) +{ + return 0; +} + static inline struct page *device_private_entry_to_page(swp_entry_t entry) { return NULL; @@ -189,6 +199,11 @@ static inline int is_write_migration_entry(swp_entry_t entry) return unlikely(swp_type(entry) == SWP_MIGRATION_WRITE); } +static inline unsigned long migration_entry_to_pfn(swp_entry_t entry) +{ + return swp_offset(entry); +} + static inline struct page *migration_entry_to_page(swp_entry_t entry) { struct page *p = pfn_to_page(swp_offset(entry)); @@ -218,6 +233,12 @@ static inline int is_migration_entry(swp_entry_t swp) { return 0; } + +static inline unsigned long migration_entry_to_pfn(swp_entry_t entry) +{ + return 0; +} + static inline struct page *migration_entry_to_page(swp_entry_t entry) { return NULL; -- cgit v1.2.3