// SPDX-License-Identifier: GPL-2.0 #include <linux/kernel.h> #include <linux/string.h> #include <linux/mm.h> #include <linux/highmem.h> #include <linux/page_ext.h> #include <linux/poison.h> #include <linux/ratelimit.h> #include <linux/kasan.h> static bool want_page_poisoning __read_mostly; static int __init early_page_poison_param(char *buf) { if (!buf) return -EINVAL; return strtobool(buf, &want_page_poisoning); } early_param("page_poison", early_page_poison_param); /** * page_poisoning_enabled - check if page poisoning is enabled * * Return true if page poisoning is enabled, or false if not. */ bool page_poisoning_enabled(void) { /* * Assumes that debug_pagealloc_enabled is set before * memblock_free_all. * Page poisoning is debug page alloc for some arches. If * either of those options are enabled, enable poisoning. */ return (want_page_poisoning || (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) && debug_pagealloc_enabled())); } EXPORT_SYMBOL_GPL(page_poisoning_enabled); static void poison_page(struct page *page) { void *addr = kmap_atomic(page); /* KASAN still think the page is in-use, so skip it. */ kasan_disable_current(); memset(addr, PAGE_POISON, PAGE_SIZE); kasan_enable_current(); 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; addr = kmap_atomic(page); /* * Page poisoning when enabled poisons each and every page * that is freed to buddy. Thus no extra check is done to * see if a page was poisoned. */ check_poison_mem(addr, PAGE_SIZE); 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