From: Sergei Trofimovich slyfox@gentoo.org Subject: mm: page_alloc: ignore init_on_free=1 for debug_pagealloc=1

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.

Link: https://lkml.kernel.org/r/20210329222555.3077928-1-slyfox@gentoo.org Link: https://lkml.org/lkml/2021/3/26/443 Fixes: 8db26a3d4735 ("mm, page_poison: use static key more efficiently") Signed-off-by: Sergei Trofimovich slyfox@gentoo.org Acked-by: Vlastimil Babka vbabka@suse.cz Reviewed-by: David Hildenbrand david@redhat.com Cc: Andrey Konovalov andreyknvl@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

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

--- a/mm/page_alloc.c~mm-page_alloc-ignore-init_on_free=1-for-debug_pagealloc=1 +++ a/mm/page_alloc.c @@ -786,32 +786,36 @@ static inline void clear_page_guard(stru */ 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; _