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 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/page_alloc.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index f3418edb136b..2d845ddfabad 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1049,6 +1049,9 @@ 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