Commit 787af64d05cd ("mm: page_alloc: validate buddy before check its migratetype.") fixes a bug in 1dd214b8f21c and there is a similar bug in d9dddbf55667 that can be fixed in a similar way too.
In unset_migratetype_isolate(), we also need the fix, so move page_is_buddy() from mm/page_alloc.c to mm/internal.h
In addition, for RISC-V arch the first 2MB RAM could be reserved for opensbi, so it would have pfn_base=512 and mem_map began with 512th PFN when CONFIG_FLATMEM=y. But __find_buddy_pfn algorithm thinks the start pfn 0, it could get 0 pfn or less than the pfn_base value. We need page_is_buddy() to verify the buddy to prevent accessing an invalid buddy.
Fixes: d9dddbf55667 ("mm/page_alloc: prevent merging between isolated and other pageblocks") Cc: stable@vger.kernel.org Reported-by: zjb194813@alibaba-inc.com Reported-by: tianhu.hh@alibaba-inc.com Signed-off-by: Xianting Tian xianting.tian@linux.alibaba.com --- mm/internal.h | 34 ++++++++++++++++++++++++++++++++++ mm/page_alloc.c | 37 +++---------------------------------- mm/page_isolation.c | 3 ++- 3 files changed, 39 insertions(+), 35 deletions(-)
diff --git a/mm/internal.h b/mm/internal.h index d80300392a19..dfa80bdfe5c6 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -386,6 +386,40 @@ static inline bool is_data_mapping(vm_flags_t flags) return (flags & (VM_WRITE | VM_SHARED | VM_STACK)) == VM_WRITE; }
+/* + * This function checks whether a page is free && is the buddy + * we can coalesce a page and its buddy if + * (a) the buddy is not in a hole (check before calling!) && + * (b) the buddy is in the buddy system && + * (c) a page and its buddy have the same order && + * (d) a page and its buddy are in the same zone. + * + * For recording whether a page is in the buddy system, we set PageBuddy. + * Setting, clearing, and testing PageBuddy is serialized by zone->lock. + * + * For recording page's order, we use page_private(page). + */ +static inline bool page_is_buddy(struct page *page, struct page *buddy, + unsigned int order) +{ + if (!page_is_guard(buddy) && !PageBuddy(buddy)) + return false; + + if (buddy_order(buddy) != order) + return false; + + /* + * zone check is done late to avoid uselessly calculating + * zone/node ids for pages that could never merge. + */ + if (page_zone_id(page) != page_zone_id(buddy)) + return false; + + VM_BUG_ON_PAGE(page_count(buddy) != 0, buddy); + + return true; +} + /* mm/util.c */ void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma, struct vm_area_struct *prev); diff --git a/mm/page_alloc.c b/mm/page_alloc.c index b1caa1c6c887..78ada8dedefb 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -886,40 +886,6 @@ static inline void set_buddy_order(struct page *page, unsigned int order) __SetPageBuddy(page); }
-/* - * This function checks whether a page is free && is the buddy - * we can coalesce a page and its buddy if - * (a) the buddy is not in a hole (check before calling!) && - * (b) the buddy is in the buddy system && - * (c) a page and its buddy have the same order && - * (d) a page and its buddy are in the same zone. - * - * For recording whether a page is in the buddy system, we set PageBuddy. - * Setting, clearing, and testing PageBuddy is serialized by zone->lock. - * - * For recording page's order, we use page_private(page). - */ -static inline bool page_is_buddy(struct page *page, struct page *buddy, - unsigned int order) -{ - if (!page_is_guard(buddy) && !PageBuddy(buddy)) - return false; - - if (buddy_order(buddy) != order) - return false; - - /* - * zone check is done late to avoid uselessly calculating - * zone/node ids for pages that could never merge. - */ - if (page_zone_id(page) != page_zone_id(buddy)) - return false; - - VM_BUG_ON_PAGE(page_count(buddy) != 0, buddy); - - return true; -} - #ifdef CONFIG_COMPACTION static inline struct capture_control *task_capc(struct zone *zone) { @@ -1129,6 +1095,9 @@ static inline void __free_one_page(struct page *page,
buddy_pfn = __find_buddy_pfn(pfn, order); buddy = page + (buddy_pfn - pfn); + + if (!page_is_buddy(page, buddy, order)) + goto done_merging; buddy_mt = get_pageblock_migratetype(buddy);
if (migratetype != buddy_mt diff --git a/mm/page_isolation.c b/mm/page_isolation.c index f67c4c70f17f..5d14cef812ee 100644 --- a/mm/page_isolation.c +++ b/mm/page_isolation.c @@ -93,7 +93,8 @@ static void unset_migratetype_isolate(struct page *page, unsigned migratetype) buddy_pfn = __find_buddy_pfn(pfn, order); buddy = page + (buddy_pfn - pfn);
- if (!is_migrate_isolate_page(buddy)) { + if (page_is_buddy(page, buddy, order) && + !is_migrate_isolate_page(buddy)) { isolated_page = !!__isolate_free_page(page, order); /* * Isolating a free page in an isolated pageblock