From 8823b1dbc05fab1a8bec275eeae4709257c2661d Mon Sep 17 00:00:00 2001 From: Laura Abbott Date: Tue, 15 Mar 2016 14:56:27 -0700 Subject: mm/page_poison.c: enable PAGE_POISONING as a separate option Page poisoning is currently set up as a feature if architectures don't have architecture debug page_alloc to allow unmapping of pages. It has uses apart from that though. Clearing of the pages on free provides an increase in security as it helps to limit the risk of information leaks. Allow page poisoning to be enabled as a separate option independent of kernel_map pages since the two features do separate work. Because of how hiberanation is implemented, the checks on alloc cannot occur if hibernation is enabled. The runtime alloc checks can also be enabled with an option when !HIBERNATION. Credit to Grsecurity/PaX team for inspiring this work Signed-off-by: Laura Abbott Cc: Rafael J. Wysocki Cc: "Kirill A. Shutemov" Cc: Vlastimil Babka Cc: Michal Hocko Cc: Kees Cook Cc: Mathias Krause Cc: Dave Hansen Cc: Jianyu Zhan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/Kconfig.debug | 25 +++++++- mm/Makefile | 2 +- mm/debug-pagealloc.c | 137 ---------------------------------------- mm/page_alloc.c | 2 + mm/page_poison.c | 173 +++++++++++++++++++++++++++++++++++++++++++++++++++ 5 files changed, 200 insertions(+), 139 deletions(-) delete mode 100644 mm/debug-pagealloc.c create mode 100644 mm/page_poison.c (limited to 'mm') diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug index a0c136af9c91..1f99f9a0deae 100644 --- a/mm/Kconfig.debug +++ b/mm/Kconfig.debug @@ -41,4 +41,27 @@ config DEBUG_PAGEALLOC_ENABLE_DEFAULT can be overridden by debug_pagealloc=off|on. config PAGE_POISONING - bool + bool "Poison pages after freeing" + select PAGE_EXTENSION + select PAGE_POISONING_NO_SANITY if HIBERNATION + ---help--- + Fill the pages with poison patterns after free_pages() and verify + the patterns before alloc_pages. The filling of the memory helps + reduce the risk of information leaks from freed data. This does + have a potential performance impact. + + Note that "poison" here is not the same thing as the "HWPoison" + for CONFIG_MEMORY_FAILURE. This is software poisoning only. + + If unsure, say N + +config PAGE_POISONING_NO_SANITY + depends on PAGE_POISONING + bool "Only poison, don't sanity check" + ---help--- + Skip the sanity checking on alloc, only fill the pages with + poison on free. This reduces some of the overhead of the + poisoning feature. + + If you are only interested in sanitization, say Y. Otherwise + say N. diff --git a/mm/Makefile b/mm/Makefile index 2ed43191fc3b..cfdd481d27a5 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -48,7 +48,7 @@ obj-$(CONFIG_SPARSEMEM_VMEMMAP) += sparse-vmemmap.o obj-$(CONFIG_SLOB) += slob.o obj-$(CONFIG_MMU_NOTIFIER) += mmu_notifier.o obj-$(CONFIG_KSM) += ksm.o -obj-$(CONFIG_PAGE_POISONING) += debug-pagealloc.o +obj-$(CONFIG_PAGE_POISONING) += page_poison.o obj-$(CONFIG_SLAB) += slab.o obj-$(CONFIG_SLUB) += slub.o obj-$(CONFIG_KMEMCHECK) += kmemcheck.o diff --git a/mm/debug-pagealloc.c b/mm/debug-pagealloc.c deleted file mode 100644 index 5bf5906ce13b..000000000000 --- a/mm/debug-pagealloc.c +++ /dev/null @@ -1,137 +0,0 @@ -#include -#include -#include -#include -#include -#include -#include - -static bool page_poisoning_enabled __read_mostly; - -static bool need_page_poisoning(void) -{ - if (!debug_pagealloc_enabled()) - return false; - - return true; -} - -static void init_page_poisoning(void) -{ - if (!debug_pagealloc_enabled()) - return; - - page_poisoning_enabled = true; -} - -struct page_ext_operations page_poisoning_ops = { - .need = need_page_poisoning, - .init = init_page_poisoning, -}; - -static inline void set_page_poison(struct page *page) -{ - struct page_ext *page_ext; - - page_ext = lookup_page_ext(page); - __set_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags); -} - -static inline void clear_page_poison(struct page *page) -{ - struct page_ext *page_ext; - - page_ext = lookup_page_ext(page); - __clear_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags); -} - -static inline bool page_poison(struct page *page) -{ - struct page_ext *page_ext; - - page_ext = lookup_page_ext(page); - return test_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags); -} - -static void poison_page(struct page *page) -{ - void *addr = kmap_atomic(page); - - set_page_poison(page); - memset(addr, PAGE_POISON, PAGE_SIZE); - kunmap_atomic(addr); -} - -static void poison_pages(struct page *page, int n) -{ - int i; - - for (i = 0; i < n; i++) - poison_page(page + i); -} - -static bool single_bit_flip(unsigned char a, unsigned char b) -{ - unsigned char error = a ^ b; - - return error && !(error & (error - 1)); -} - -static void check_poison_mem(unsigned char *mem, size_t bytes) -{ - static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10); - unsigned char *start; - unsigned char *end; - - start = memchr_inv(mem, PAGE_POISON, bytes); - if (!start) - return; - - for (end = mem + bytes - 1; end > start; end--) { - if (*end != PAGE_POISON) - break; - } - - if (!__ratelimit(&ratelimit)) - return; - else if (start == end && single_bit_flip(*start, PAGE_POISON)) - printk(KERN_ERR "pagealloc: single bit error\n"); - else - printk(KERN_ERR "pagealloc: memory corruption\n"); - - print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start, - end - start + 1, 1); - dump_stack(); -} - -static void unpoison_page(struct page *page) -{ - void *addr; - - if (!page_poison(page)) - return; - - addr = kmap_atomic(page); - check_poison_mem(addr, PAGE_SIZE); - clear_page_poison(page); - kunmap_atomic(addr); -} - -static void unpoison_pages(struct page *page, int n) -{ - int i; - - for (i = 0; i < n; i++) - unpoison_page(page + i); -} - -void __kernel_map_pages(struct page *page, int numpages, int enable) -{ - if (!page_poisoning_enabled) - return; - - if (enable) - unpoison_pages(page, numpages); - else - poison_pages(page, numpages); -} diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 0691403aed93..2a08349fbab2 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1025,6 +1025,7 @@ static bool free_pages_prepare(struct page *page, unsigned int order) PAGE_SIZE << order); } arch_free_page(page, order); + kernel_poison_pages(page, 1 << order, 0); kernel_map_pages(page, 1 << order, 0); return true; @@ -1420,6 +1421,7 @@ static int prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags, arch_alloc_page(page, order); kernel_map_pages(page, 1 << order, 1); + kernel_poison_pages(page, 1 << order, 1); kasan_alloc_pages(page, order); if (gfp_flags & __GFP_ZERO) diff --git a/mm/page_poison.c b/mm/page_poison.c new file mode 100644 index 000000000000..89d3bc773633 --- /dev/null +++ b/mm/page_poison.c @@ -0,0 +1,173 @@ +#include +#include +#include +#include +#include +#include +#include + +static bool __page_poisoning_enabled __read_mostly; +static bool want_page_poisoning __read_mostly; + +static int early_page_poison_param(char *buf) +{ + if (!buf) + return -EINVAL; + + if (strcmp(buf, "on") == 0) + want_page_poisoning = true; + else if (strcmp(buf, "off") == 0) + want_page_poisoning = false; + + return 0; +} +early_param("page_poison", early_page_poison_param); + +bool page_poisoning_enabled(void) +{ + return __page_poisoning_enabled; +} + +static bool need_page_poisoning(void) +{ + return want_page_poisoning; +} + +static void init_page_poisoning(void) +{ + /* + * page poisoning is debug page alloc for some arches. If either + * of those options are enabled, enable poisoning + */ + if (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC)) { + if (!want_page_poisoning && !debug_pagealloc_enabled()) + return; + } else { + if (!want_page_poisoning) + return; + } + + __page_poisoning_enabled = true; +} + +struct page_ext_operations page_poisoning_ops = { + .need = need_page_poisoning, + .init = init_page_poisoning, +}; + +static inline void set_page_poison(struct page *page) +{ + struct page_ext *page_ext; + + page_ext = lookup_page_ext(page); + __set_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags); +} + +static inline void clear_page_poison(struct page *page) +{ + struct page_ext *page_ext; + + page_ext = lookup_page_ext(page); + __clear_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags); +} + +static inline bool page_poison(struct page *page) +{ + struct page_ext *page_ext; + + page_ext = lookup_page_ext(page); + return test_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags); +} + +static void poison_page(struct page *page) +{ + void *addr = kmap_atomic(page); + + set_page_poison(page); + memset(addr, PAGE_POISON, PAGE_SIZE); + kunmap_atomic(addr); +} + +static void poison_pages(struct page *page, int n) +{ + int i; + + for (i = 0; i < n; i++) + poison_page(page + i); +} + +static bool single_bit_flip(unsigned char a, unsigned char b) +{ + unsigned char error = a ^ b; + + return error && !(error & (error - 1)); +} + +static void check_poison_mem(unsigned char *mem, size_t bytes) +{ + static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10); + unsigned char *start; + unsigned char *end; + + if (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY)) + return; + + start = memchr_inv(mem, PAGE_POISON, bytes); + if (!start) + return; + + for (end = mem + bytes - 1; end > start; end--) { + if (*end != PAGE_POISON) + break; + } + + if (!__ratelimit(&ratelimit)) + return; + else if (start == end && single_bit_flip(*start, PAGE_POISON)) + pr_err("pagealloc: single bit error\n"); + else + pr_err("pagealloc: memory corruption\n"); + + print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start, + end - start + 1, 1); + dump_stack(); +} + +static void unpoison_page(struct page *page) +{ + void *addr; + + if (!page_poison(page)) + return; + + addr = kmap_atomic(page); + check_poison_mem(addr, PAGE_SIZE); + clear_page_poison(page); + kunmap_atomic(addr); +} + +static void unpoison_pages(struct page *page, int n) +{ + int i; + + for (i = 0; i < n; i++) + unpoison_page(page + i); +} + +void kernel_poison_pages(struct page *page, int numpages, int enable) +{ + if (!page_poisoning_enabled()) + return; + + if (enable) + unpoison_pages(page, numpages); + else + poison_pages(page, numpages); +} + +#ifndef CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC +void __kernel_map_pages(struct page *page, int numpages, int enable) +{ + /* This function does nothing, all work is done via poison pages */ +} +#endif -- cgit v1.2.3