On !ARCH_SUPPORTS_DEBUG_PAGEALLOC (like ia64) debug_pagealloc=1 implies page_poison=on:

if (page_poisoning_enabled() || (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) && debug_pagealloc_enabled())) static_branch_enable(&_page_poisoning_enabled);

page_poison=on needs to override init_on_free=1.

Before the change it did not work as expected for the following case: - have PAGE_POISONING=y - have page_poison unset - have !ARCH_SUPPORTS_DEBUG_PAGEALLOC arch (like ia64) - have init_on_free=1 - have debug_pagealloc=1

That way we get both keys enabled: - static_branch_enable(&init_on_free); - static_branch_enable(&_page_poisoning_enabled);

which leads to poisoned pages returned for __GFP_ZERO pages.

After the change we execute only: - static_branch_enable(&_page_poisoning_enabled); and ignore init_on_free=1.

Acked-by: Vlastimil Babka vbabka@suse.cz Fixes: 8db26a3d4735 ("mm, page_poison: use static key more efficiently") Cc: stable@vger.kernel.org CC: Andrew Morton akpm@linux-foundation.org CC: linux-mm@kvack.org CC: David Hildenbrand david@redhat.com CC: Andrey Konovalov andreyknvl@gmail.com Link: https://lkml.org/lkml/2021/3/26/443

Signed-off-by: Sergei Trofimovich slyfox@gentoo.org --- Change since v2: - Added 'Fixes:' and 'CC: stable@' suggested by Vlastimil and David - Renamed local variable to 'page_poisoning_requested' for consistency suggested by David - Simplified initialization of page_poisoning_requested suggested by David - Added 'Acked-by: Vlastimil'

mm/page_alloc.c | 30 +++++++++++++++++------------- 1 file changed, 17 insertions(+), 13 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c index cfc72873961d..4bb3cdfc47f8 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -764,32 +764,36 @@ static inline void clear_page_guard(struct zone *zone, struct page *page, */ void init_mem_debugging_and_hardening(void) { + bool page_poisoning_requested = false; + +#ifdef CONFIG_PAGE_POISONING + /* + * Page poisoning is debug page alloc for some arches. If + * either of those options are enabled, enable poisoning. + */ + if (page_poisoning_enabled() || + (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) && + debug_pagealloc_enabled())) { + static_branch_enable(&_page_poisoning_enabled); + page_poisoning_requested = true; + } +#endif + if (_init_on_alloc_enabled_early) { - if (page_poisoning_enabled()) + if (page_poisoning_requested) pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, " "will take precedence over init_on_alloc\n"); else static_branch_enable(&init_on_alloc); } if (_init_on_free_enabled_early) { - if (page_poisoning_enabled()) + if (page_poisoning_requested) pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, " "will take precedence over init_on_free\n"); else static_branch_enable(&init_on_free); }

-#ifdef CONFIG_PAGE_POISONING - /* - * Page poisoning is debug page alloc for some arches. If - * either of those options are enabled, enable poisoning. - */ - if (page_poisoning_enabled() || - (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) && - debug_pagealloc_enabled())) - static_branch_enable(&_page_poisoning_enabled); -#endif - #ifdef CONFIG_DEBUG_PAGEALLOC if (!debug_pagealloc_enabled()) return;