On 9/12/19 7:05 PM, Andrey Ryabinin wrote: > > Or another alternative option (and actually easier one to implement), leave PAGE_OWNER as is (no "select"s in Kconfigs) > Make PAGE_OWNER_FREE_STACK like this: > > +config PAGE_OWNER_FREE_STACK > + def_bool KASAN || DEBUG_PAGEALLOC > + depends on PAGE_OWNER > + > > So, users that want alloc/free stack will have to enable CONFIG_PAGE_OWNER=y and add page_owner=on to boot cmdline. > > > Basically the difference between these alternative is whether we enable page_owner by default or not. But there is always a possibility to disable it. OK, how about this? BTW, the bugzilla [1] also mentions that on overflow we might be dumping the wrong page (including stacks). I'll leave that to somebody familiar with KASAN internals though. [1] https://bugzilla.kernel.org/show_bug.cgi?id=203967 ----8<---- >From 887e3c092c073d996098ac2b101b0feaef110b54 Mon Sep 17 00:00:00 2001 From: Vlastimil Babka <vbabka@xxxxxxx> Date: Mon, 16 Sep 2019 11:28:19 +0200 Subject: [PATCH] mm, debug, kasan: save and dump freeing stack trace for kasan The commit "mm, page_owner, debug_pagealloc: save and dump freeing stack trace" enhanced page_owner to also store freeing stack trace, when debug_pagealloc is also enabled. KASAN would also like to do this [1] to improve error reports to debug e.g. UAF issues. This patch therefore introduces a helper config option PAGE_OWNER_FREE_STACK, which is enabled when PAGE_OWNER and either of DEBUG_PAGEALLOC or KASAN is enabled. Boot-time, the free stack saving is enabled when booting a KASAN kernel with page_owner=on, or non-KASAN kernel with debug_pagealloc=on and page_owner=on. [1] https://bugzilla.kernel.org/show_bug.cgi?id=203967 Suggested-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Suggested-by: Walter Wu <walter-zh.wu@xxxxxxxxxxxx> Suggested-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx> --- Documentation/dev-tools/kasan.rst | 4 ++++ include/linux/page_owner.h | 1 + mm/Kconfig.debug | 4 ++++ mm/page_alloc.c | 6 +++++- mm/page_owner.c | 35 +++++++++++++++++++------------ 5 files changed, 36 insertions(+), 14 deletions(-) diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst index b72d07d70239..434e605030e9 100644 --- a/Documentation/dev-tools/kasan.rst +++ b/Documentation/dev-tools/kasan.rst @@ -41,6 +41,10 @@ smaller binary while the latter is 1.1 - 2 times faster. Both KASAN modes work with both SLUB and SLAB memory allocators. For better bug detection and nicer reporting, enable CONFIG_STACKTRACE. +To augment reports with last allocation and freeing stack of the physical +page, it is recommended to configure kernel also with CONFIG_PAGE_OWNER = y +and boot with page_owner=on. + To disable instrumentation for specific files or directories, add a line similar to the following to the respective kernel Makefile: diff --git a/include/linux/page_owner.h b/include/linux/page_owner.h index 8679ccd722e8..6ffe8b81ba85 100644 --- a/include/linux/page_owner.h +++ b/include/linux/page_owner.h @@ -6,6 +6,7 @@ #ifdef CONFIG_PAGE_OWNER extern struct static_key_false page_owner_inited; +extern bool page_owner_free_stack_disabled; extern struct page_ext_operations page_owner_ops; extern void __reset_page_owner(struct page *page, unsigned int order); diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug index 327b3ebf23bf..1ea247da3322 100644 --- a/mm/Kconfig.debug +++ b/mm/Kconfig.debug @@ -62,6 +62,10 @@ config PAGE_OWNER If unsure, say N. +config PAGE_OWNER_FREE_STACK + def_bool KASAN || DEBUG_PAGEALLOC + depends on PAGE_OWNER + config PAGE_POISONING bool "Poison pages after freeing" select PAGE_POISONING_NO_SANITY if HIBERNATION diff --git a/mm/page_alloc.c b/mm/page_alloc.c index c5d62f1c2851..d9e44671af3f 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -710,8 +710,12 @@ static int __init early_debug_pagealloc(char *buf) if (kstrtobool(buf, &enable)) return -EINVAL; - if (enable) + if (enable) { static_branch_enable(&_debug_pagealloc_enabled); +#ifdef CONFIG_PAGE_OWNER + page_owner_free_stack_disabled = false; +#endif + } return 0; } diff --git a/mm/page_owner.c b/mm/page_owner.c index dee931184788..b589bfbc4795 100644 --- a/mm/page_owner.c +++ b/mm/page_owner.c @@ -24,13 +24,15 @@ struct page_owner { short last_migrate_reason; gfp_t gfp_mask; depot_stack_handle_t handle; -#ifdef CONFIG_DEBUG_PAGEALLOC +#ifdef CONFIG_PAGE_OWNER_FREE_STACK depot_stack_handle_t free_handle; #endif }; static bool page_owner_disabled = true; +bool page_owner_free_stack_disabled = true; DEFINE_STATIC_KEY_FALSE(page_owner_inited); +static DEFINE_STATIC_KEY_FALSE(page_owner_free_stack); static depot_stack_handle_t dummy_handle; static depot_stack_handle_t failure_handle; @@ -46,6 +48,9 @@ static int __init early_page_owner_param(char *buf) if (strcmp(buf, "on") == 0) page_owner_disabled = false; + if (!page_owner_disabled && IS_ENABLED(CONFIG_KASAN)) + page_owner_free_stack_disabled = false; + return 0; } early_param("page_owner", early_page_owner_param); @@ -91,6 +96,8 @@ static void init_page_owner(void) register_failure_stack(); register_early_stack(); static_branch_enable(&page_owner_inited); + if (!page_owner_free_stack_disabled) + static_branch_enable(&page_owner_free_stack); init_early_allocated_pages(); } @@ -148,11 +155,11 @@ void __reset_page_owner(struct page *page, unsigned int order) { int i; struct page_ext *page_ext; -#ifdef CONFIG_DEBUG_PAGEALLOC +#ifdef CONFIG_PAGE_OWNER_FREE_STACK depot_stack_handle_t handle = 0; struct page_owner *page_owner; - if (debug_pagealloc_enabled()) + if (static_branch_unlikely(&page_owner_free_stack)) handle = save_stack(GFP_NOWAIT | __GFP_NOWARN); #endif @@ -161,8 +168,8 @@ void __reset_page_owner(struct page *page, unsigned int order) if (unlikely(!page_ext)) continue; __clear_bit(PAGE_EXT_OWNER_ACTIVE, &page_ext->flags); -#ifdef CONFIG_DEBUG_PAGEALLOC - if (debug_pagealloc_enabled()) { +#ifdef CONFIG_PAGE_OWNER_FREE_STACK + if (static_branch_unlikely(&page_owner_free_stack)) { page_owner = get_page_owner(page_ext); page_owner->free_handle = handle; } @@ -451,14 +458,16 @@ void __dump_page_owner(struct page *page) stack_trace_print(entries, nr_entries, 0); } -#ifdef CONFIG_DEBUG_PAGEALLOC - handle = READ_ONCE(page_owner->free_handle); - if (!handle) { - pr_alert("page_owner free stack trace missing\n"); - } else { - nr_entries = stack_depot_fetch(handle, &entries); - pr_alert("page last free stack trace:\n"); - stack_trace_print(entries, nr_entries, 0); +#ifdef CONFIG_PAGE_OWNER_FREE_STACK + if (static_branch_unlikely(&page_owner_free_stack)) { + handle = READ_ONCE(page_owner->free_handle); + if (!handle) { + pr_alert("page_owner free stack trace missing\n"); + } else { + nr_entries = stack_depot_fetch(handle, &entries); + pr_alert("page last free stack trace:\n"); + stack_trace_print(entries, nr_entries, 0); + } } #endif -- 2.23.0
