From 862b6dee20b0db2ebaa728c302a1b296ff144de3 Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Mon, 14 Dec 2020 19:11:15 -0800 Subject: [PATCH] mm/page_alloc: clear all pages in post_alloc_hook() with init_on_alloc=1 commit 6471384af2a6 ("mm: security: introduce init_on_alloc=1 and init_on_free=1 boot options") resulted with init_on_alloc=1 in all pages leaving the buddy via alloc_pages() and friends to be initialized/cleared/zeroed on allocation. However, the same logic is currently not applied to alloc_contig_pages(): allocated pages leaving the buddy aren't cleared with init_on_alloc=1 and init_on_free=0. Let's also properly clear pages on that allocation path. To achieve that, let's move clearing into post_alloc_hook(). This will not only affect alloc_contig_pages() allocations but also any pages used as migration target in compaction code via compaction_alloc(). While this sounds sub-optimal, it's the very same handling as when allocating migration targets via alloc_migration_target() - pages will get properly cleared with init_on_free=1. In case we ever want to optimize migration in that regard, we should tackle all such migration users - if we believe migration code can be fully trusted. With this change, we will see double clearing of pages in some cases. One example are gigantic pages (either allocated via CMA, or allocated dynamically via alloc_contig_pages()) - which is the right thing to do (and to be optimized outside of the buddy in the callers) as discussed in: https://lkml.kernel.org/r/20201019182853.7467-1-gpiccoli@canonical.com This change implies that with init_on_alloc=1 - All CMA allocations will be cleared - Gigantic pages allocated via alloc_contig_pages() will be cleared - virtio-mem memory to be unplugged will be cleared. While this is suboptimal, it's similar to memory balloon drivers handling, where all pages to be inflated will get cleared as well. - Pages isolated for compaction will be cleared Link: https://lkml.kernel.org/r/20201120180452.19071-1-david@redhat.com Signed-off-by: David Hildenbrand Acked-by: Vlastimil Babka Acked-by: Michal Hocko Cc: Alexander Potapenko Cc: Mike Kravetz Cc: Mike Rapoport Cc: Oscar Salvador Cc: Kees Cook Cc: Michael Ellerman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/page_alloc.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index f4d415e4b9db..371a22eb3180 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2284,6 +2284,9 @@ inline void post_alloc_hook(struct page *page, unsigned int order, kasan_alloc_pages(page, order); kernel_poison_pages(page, 1 << order, 1); set_page_owner(page, order, gfp_flags); + + if (!free_pages_prezeroed() && want_init_on_alloc(gfp_flags)) + kernel_init_free_pages(page, 1 << order); } static void prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags, @@ -2291,9 +2294,6 @@ static void prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags { post_alloc_hook(page, order, gfp_flags); - if (!free_pages_prezeroed() && want_init_on_alloc(gfp_flags)) - kernel_init_free_pages(page, 1 << order); - if (order && (gfp_flags & __GFP_COMP)) prep_compound_page(page, order);