From: Vlastimil Babka <vbabka@xxxxxxx> Subject: mm, page_alloc: do not rely on the order of page_poison and init_on_alloc/free parameters Patch series "cleanup page poisoning", v3. I have identified a number of issues and opportunities for cleanup with CONFIG_PAGE_POISON and friends: - interaction with init_on_alloc and init_on_free parameters depends on the order of parameters (Patch 1) - the boot time enabling uses static key, but inefficienty (Patch 2) - sanity checking is incompatible with hibernation (Patch 3) - CONFIG_PAGE_POISONING_NO_SANITY can be removed now that we have init_on_free (Patch 4) - CONFIG_PAGE_POISONING_ZERO can be most likely removed now that we have init_on_free (Patch 5) This patch (of 5): Enabling page_poison=1 together with init_on_alloc=1 or init_on_free=1 produces a warning in dmesg that page_poison takes precedence. However, as these warnings are printed in early_param handlers for init_on_alloc/free, they are not printed if page_poison is enabled later on the command line (handlers are called in the order of their parameters), or when init_on_alloc/free is always enabled by the respective config option - before the page_poison early param handler is called, it is not considered to be enabled. This is inconsistent. We can remove the dependency on order by making the init_on_* parameters only set a boolean variable, and postponing the evaluation after all early params have been processed. Introduce a new init_mem_debugging_and_hardening() function for that, and move the related debug_pagealloc processing there as well. As a result init_mem_debugging_and_hardening() knows always accurately if init_on_* and/or page_poison options were enabled. Thus we can also optimize want_init_on_alloc() and want_init_on_free(). We don't need to check page_poisoning_enabled() there, we can instead not enable the init_on_* static keys at all, if page poisoning is enabled. This results in a simpler and more effective code. Link: https://lkml.kernel.org/r/20201113104033.22907-1-vbabka@xxxxxxx Link: https://lkml.kernel.org/r/20201113104033.22907-2-vbabka@xxxxxxx Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx> Reviewed-by: Mike Rapoport <rppt@xxxxxxxxxxxxx> Cc: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> Cc: Alexander Potapenko <glider@xxxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: Mateusz Nosek <mateusznosek0@xxxxxxxxx> Cc: Laura Abbott <labbott@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/mm.h | 20 +-------- init/main.c | 2 mm/page_alloc.c | 88 ++++++++++++++++++++----------------------- 3 files changed, 46 insertions(+), 64 deletions(-) --- a/include/linux/mm.h~mm-page_alloc-do-not-rely-on-the-order-of-page_poison-and-init_on_alloc-free-parameters +++ a/include/linux/mm.h @@ -2872,6 +2872,7 @@ extern int apply_to_existing_page_range( unsigned long address, unsigned long size, pte_fn_t fn, void *data); +extern void init_mem_debugging_and_hardening(void); #ifdef CONFIG_PAGE_POISONING extern bool page_poisoning_enabled(void); extern void kernel_poison_pages(struct page *page, int numpages, int enable); @@ -2881,35 +2882,20 @@ static inline void kernel_poison_pages(s int enable) { } #endif -#ifdef CONFIG_INIT_ON_ALLOC_DEFAULT_ON -DECLARE_STATIC_KEY_TRUE(init_on_alloc); -#else DECLARE_STATIC_KEY_FALSE(init_on_alloc); -#endif static inline bool want_init_on_alloc(gfp_t flags) { - if (static_branch_unlikely(&init_on_alloc) && - !page_poisoning_enabled()) + if (static_branch_unlikely(&init_on_alloc)) return true; return flags & __GFP_ZERO; } -#ifdef CONFIG_INIT_ON_FREE_DEFAULT_ON -DECLARE_STATIC_KEY_TRUE(init_on_free); -#else DECLARE_STATIC_KEY_FALSE(init_on_free); -#endif static inline bool want_init_on_free(void) { - return static_branch_unlikely(&init_on_free) && - !page_poisoning_enabled(); + return static_branch_unlikely(&init_on_free); } -#ifdef CONFIG_DEBUG_PAGEALLOC -extern void init_debug_pagealloc(void); -#else -static inline void init_debug_pagealloc(void) {} -#endif extern bool _debug_pagealloc_enabled_early; DECLARE_STATIC_KEY_FALSE(_debug_pagealloc_enabled); --- a/init/main.c~mm-page_alloc-do-not-rely-on-the-order-of-page_poison-and-init_on_alloc-free-parameters +++ a/init/main.c @@ -824,7 +824,7 @@ static void __init mm_init(void) * bigger than MAX_ORDER unless SPARSEMEM. */ page_ext_init_flatmem(); - init_debug_pagealloc(); + init_mem_debugging_and_hardening(); report_meminit(); mem_init(); /* page_owner must be initialized after buddy is ready */ --- a/mm/page_alloc.c~mm-page_alloc-do-not-rely-on-the-order-of-page_poison-and-init_on_alloc-free-parameters +++ a/mm/page_alloc.c @@ -167,53 +167,26 @@ unsigned long totalcma_pages __read_most int percpu_pagelist_fraction; gfp_t gfp_allowed_mask __read_mostly = GFP_BOOT_MASK; -#ifdef CONFIG_INIT_ON_ALLOC_DEFAULT_ON -DEFINE_STATIC_KEY_TRUE(init_on_alloc); -#else DEFINE_STATIC_KEY_FALSE(init_on_alloc); -#endif EXPORT_SYMBOL(init_on_alloc); -#ifdef CONFIG_INIT_ON_FREE_DEFAULT_ON -DEFINE_STATIC_KEY_TRUE(init_on_free); -#else DEFINE_STATIC_KEY_FALSE(init_on_free); -#endif EXPORT_SYMBOL(init_on_free); +static bool _init_on_alloc_enabled_early __read_mostly + = IS_ENABLED(CONFIG_INIT_ON_ALLOC_DEFAULT_ON); static int __init early_init_on_alloc(char *buf) { - int ret; - bool bool_result; - ret = kstrtobool(buf, &bool_result); - if (ret) - return ret; - if (bool_result && page_poisoning_enabled()) - pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, will take precedence over init_on_alloc\n"); - if (bool_result) - static_branch_enable(&init_on_alloc); - else - static_branch_disable(&init_on_alloc); - return 0; + return kstrtobool(buf, &_init_on_alloc_enabled_early); } early_param("init_on_alloc", early_init_on_alloc); +static bool _init_on_free_enabled_early __read_mostly + = IS_ENABLED(CONFIG_INIT_ON_FREE_DEFAULT_ON); static int __init early_init_on_free(char *buf) { - int ret; - bool bool_result; - - ret = kstrtobool(buf, &bool_result); - if (ret) - return ret; - if (bool_result && page_poisoning_enabled()) - pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, will take precedence over init_on_free\n"); - if (bool_result) - static_branch_enable(&init_on_free); - else - static_branch_disable(&init_on_free); - return 0; + return kstrtobool(buf, &_init_on_free_enabled_early); } early_param("init_on_free", early_init_on_free); @@ -730,19 +703,6 @@ static int __init early_debug_pagealloc( } early_param("debug_pagealloc", early_debug_pagealloc); -void init_debug_pagealloc(void) -{ - if (!debug_pagealloc_enabled()) - return; - - static_branch_enable(&_debug_pagealloc_enabled); - - if (!debug_guardpage_minorder()) - return; - - static_branch_enable(&_debug_guardpage_enabled); -} - static int __init debug_guardpage_minorder_setup(char *buf) { unsigned long res; @@ -794,6 +754,42 @@ static inline void clear_page_guard(stru unsigned int order, int migratetype) {} #endif +/* + * Enable static keys related to various memory debugging and hardening options. + * Some override others, and depend on early params that are evaluated in the + * order of appearance. So we need to first gather the full picture of what was + * enabled, and then make decisions. + */ +void init_mem_debugging_and_hardening(void) +{ + if (_init_on_alloc_enabled_early) { + if (page_poisoning_enabled()) + 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()) + 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_DEBUG_PAGEALLOC + if (!debug_pagealloc_enabled()) + return; + + static_branch_enable(&_debug_pagealloc_enabled); + + if (!debug_guardpage_minorder()) + return; + + static_branch_enable(&_debug_guardpage_enabled); +#endif +} + static inline void set_buddy_order(struct page *page, unsigned int order) { set_page_private(page, order); _
