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533 lines
15 KiB
533 lines
15 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* This file contains KASAN runtime code that manages shadow memory for |
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* generic and software tag-based KASAN modes. |
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* |
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* Copyright (c) 2014 Samsung Electronics Co., Ltd. |
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* Author: Andrey Ryabinin <[email protected]> |
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* |
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* Some code borrowed from https://github.com/xairy/kasan-prototype by |
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* Andrey Konovalov <[email protected]> |
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*/ |
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#include <linux/init.h> |
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#include <linux/kasan.h> |
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#include <linux/kernel.h> |
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#include <linux/kfence.h> |
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#include <linux/kmemleak.h> |
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#include <linux/memory.h> |
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#include <linux/mm.h> |
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#include <linux/string.h> |
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#include <linux/types.h> |
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#include <linux/vmalloc.h> |
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#include <asm/cacheflush.h> |
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#include <asm/tlbflush.h> |
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#include "kasan.h" |
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bool __kasan_check_read(const volatile void *p, unsigned int size) |
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{ |
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return kasan_check_range((unsigned long)p, size, false, _RET_IP_); |
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} |
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EXPORT_SYMBOL(__kasan_check_read); |
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bool __kasan_check_write(const volatile void *p, unsigned int size) |
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{ |
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return kasan_check_range((unsigned long)p, size, true, _RET_IP_); |
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} |
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EXPORT_SYMBOL(__kasan_check_write); |
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#undef memset |
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void *memset(void *addr, int c, size_t len) |
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{ |
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if (!kasan_check_range((unsigned long)addr, len, true, _RET_IP_)) |
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return NULL; |
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return __memset(addr, c, len); |
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} |
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#ifdef __HAVE_ARCH_MEMMOVE |
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#undef memmove |
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void *memmove(void *dest, const void *src, size_t len) |
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{ |
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if (!kasan_check_range((unsigned long)src, len, false, _RET_IP_) || |
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!kasan_check_range((unsigned long)dest, len, true, _RET_IP_)) |
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return NULL; |
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return __memmove(dest, src, len); |
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} |
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#endif |
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#undef memcpy |
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void *memcpy(void *dest, const void *src, size_t len) |
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{ |
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if (!kasan_check_range((unsigned long)src, len, false, _RET_IP_) || |
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!kasan_check_range((unsigned long)dest, len, true, _RET_IP_)) |
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return NULL; |
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return __memcpy(dest, src, len); |
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} |
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void kasan_poison(const void *addr, size_t size, u8 value, bool init) |
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{ |
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void *shadow_start, *shadow_end; |
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if (!kasan_arch_is_ready()) |
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return; |
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/* |
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* Perform shadow offset calculation based on untagged address, as |
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* some of the callers (e.g. kasan_poison_object_data) pass tagged |
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* addresses to this function. |
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*/ |
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addr = kasan_reset_tag(addr); |
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/* Skip KFENCE memory if called explicitly outside of sl*b. */ |
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if (is_kfence_address(addr)) |
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return; |
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if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK)) |
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return; |
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if (WARN_ON(size & KASAN_GRANULE_MASK)) |
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return; |
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shadow_start = kasan_mem_to_shadow(addr); |
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shadow_end = kasan_mem_to_shadow(addr + size); |
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__memset(shadow_start, value, shadow_end - shadow_start); |
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} |
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EXPORT_SYMBOL(kasan_poison); |
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#ifdef CONFIG_KASAN_GENERIC |
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void kasan_poison_last_granule(const void *addr, size_t size) |
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{ |
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if (!kasan_arch_is_ready()) |
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return; |
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if (size & KASAN_GRANULE_MASK) { |
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u8 *shadow = (u8 *)kasan_mem_to_shadow(addr + size); |
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*shadow = size & KASAN_GRANULE_MASK; |
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} |
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} |
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#endif |
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void kasan_unpoison(const void *addr, size_t size, bool init) |
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{ |
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u8 tag = get_tag(addr); |
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/* |
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* Perform shadow offset calculation based on untagged address, as |
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* some of the callers (e.g. kasan_unpoison_object_data) pass tagged |
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* addresses to this function. |
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*/ |
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addr = kasan_reset_tag(addr); |
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/* |
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* Skip KFENCE memory if called explicitly outside of sl*b. Also note |
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* that calls to ksize(), where size is not a multiple of machine-word |
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* size, would otherwise poison the invalid portion of the word. |
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*/ |
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if (is_kfence_address(addr)) |
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return; |
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if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK)) |
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return; |
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/* Unpoison all granules that cover the object. */ |
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kasan_poison(addr, round_up(size, KASAN_GRANULE_SIZE), tag, false); |
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/* Partially poison the last granule for the generic mode. */ |
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if (IS_ENABLED(CONFIG_KASAN_GENERIC)) |
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kasan_poison_last_granule(addr, size); |
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} |
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#ifdef CONFIG_MEMORY_HOTPLUG |
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static bool shadow_mapped(unsigned long addr) |
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{ |
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pgd_t *pgd = pgd_offset_k(addr); |
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p4d_t *p4d; |
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pud_t *pud; |
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pmd_t *pmd; |
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pte_t *pte; |
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if (pgd_none(*pgd)) |
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return false; |
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p4d = p4d_offset(pgd, addr); |
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if (p4d_none(*p4d)) |
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return false; |
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pud = pud_offset(p4d, addr); |
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if (pud_none(*pud)) |
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return false; |
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/* |
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* We can't use pud_large() or pud_huge(), the first one is |
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* arch-specific, the last one depends on HUGETLB_PAGE. So let's abuse |
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* pud_bad(), if pud is bad then it's bad because it's huge. |
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*/ |
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if (pud_bad(*pud)) |
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return true; |
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pmd = pmd_offset(pud, addr); |
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if (pmd_none(*pmd)) |
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return false; |
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if (pmd_bad(*pmd)) |
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return true; |
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pte = pte_offset_kernel(pmd, addr); |
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return !pte_none(*pte); |
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} |
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static int __meminit kasan_mem_notifier(struct notifier_block *nb, |
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unsigned long action, void *data) |
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{ |
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struct memory_notify *mem_data = data; |
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unsigned long nr_shadow_pages, start_kaddr, shadow_start; |
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unsigned long shadow_end, shadow_size; |
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nr_shadow_pages = mem_data->nr_pages >> KASAN_SHADOW_SCALE_SHIFT; |
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start_kaddr = (unsigned long)pfn_to_kaddr(mem_data->start_pfn); |
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shadow_start = (unsigned long)kasan_mem_to_shadow((void *)start_kaddr); |
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shadow_size = nr_shadow_pages << PAGE_SHIFT; |
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shadow_end = shadow_start + shadow_size; |
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if (WARN_ON(mem_data->nr_pages % KASAN_GRANULE_SIZE) || |
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WARN_ON(start_kaddr % KASAN_MEMORY_PER_SHADOW_PAGE)) |
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return NOTIFY_BAD; |
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switch (action) { |
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case MEM_GOING_ONLINE: { |
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void *ret; |
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/* |
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* If shadow is mapped already than it must have been mapped |
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* during the boot. This could happen if we onlining previously |
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* offlined memory. |
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*/ |
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if (shadow_mapped(shadow_start)) |
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return NOTIFY_OK; |
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ret = __vmalloc_node_range(shadow_size, PAGE_SIZE, shadow_start, |
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shadow_end, GFP_KERNEL, |
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PAGE_KERNEL, VM_NO_GUARD, |
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pfn_to_nid(mem_data->start_pfn), |
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__builtin_return_address(0)); |
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if (!ret) |
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return NOTIFY_BAD; |
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kmemleak_ignore(ret); |
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return NOTIFY_OK; |
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} |
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case MEM_CANCEL_ONLINE: |
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case MEM_OFFLINE: { |
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struct vm_struct *vm; |
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/* |
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* shadow_start was either mapped during boot by kasan_init() |
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* or during memory online by __vmalloc_node_range(). |
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* In the latter case we can use vfree() to free shadow. |
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* Non-NULL result of the find_vm_area() will tell us if |
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* that was the second case. |
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* |
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* Currently it's not possible to free shadow mapped |
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* during boot by kasan_init(). It's because the code |
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* to do that hasn't been written yet. So we'll just |
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* leak the memory. |
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*/ |
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vm = find_vm_area((void *)shadow_start); |
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if (vm) |
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vfree((void *)shadow_start); |
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} |
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} |
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return NOTIFY_OK; |
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} |
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static int __init kasan_memhotplug_init(void) |
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{ |
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hotplug_memory_notifier(kasan_mem_notifier, 0); |
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return 0; |
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} |
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core_initcall(kasan_memhotplug_init); |
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#endif |
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#ifdef CONFIG_KASAN_VMALLOC |
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static int kasan_populate_vmalloc_pte(pte_t *ptep, unsigned long addr, |
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void *unused) |
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{ |
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unsigned long page; |
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pte_t pte; |
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if (likely(!pte_none(*ptep))) |
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return 0; |
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page = __get_free_page(GFP_KERNEL); |
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if (!page) |
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return -ENOMEM; |
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memset((void *)page, KASAN_VMALLOC_INVALID, PAGE_SIZE); |
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pte = pfn_pte(PFN_DOWN(__pa(page)), PAGE_KERNEL); |
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spin_lock(&init_mm.page_table_lock); |
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if (likely(pte_none(*ptep))) { |
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set_pte_at(&init_mm, addr, ptep, pte); |
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page = 0; |
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} |
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spin_unlock(&init_mm.page_table_lock); |
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if (page) |
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free_page(page); |
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return 0; |
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} |
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int kasan_populate_vmalloc(unsigned long addr, unsigned long size) |
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{ |
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unsigned long shadow_start, shadow_end; |
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int ret; |
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if (!is_vmalloc_or_module_addr((void *)addr)) |
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return 0; |
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shadow_start = (unsigned long)kasan_mem_to_shadow((void *)addr); |
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shadow_start = ALIGN_DOWN(shadow_start, PAGE_SIZE); |
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shadow_end = (unsigned long)kasan_mem_to_shadow((void *)addr + size); |
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shadow_end = ALIGN(shadow_end, PAGE_SIZE); |
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ret = apply_to_page_range(&init_mm, shadow_start, |
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shadow_end - shadow_start, |
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kasan_populate_vmalloc_pte, NULL); |
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if (ret) |
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return ret; |
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flush_cache_vmap(shadow_start, shadow_end); |
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/* |
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* We need to be careful about inter-cpu effects here. Consider: |
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* |
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* CPU#0 CPU#1 |
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* WRITE_ONCE(p, vmalloc(100)); while (x = READ_ONCE(p)) ; |
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* p[99] = 1; |
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* |
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* With compiler instrumentation, that ends up looking like this: |
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* |
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* CPU#0 CPU#1 |
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* // vmalloc() allocates memory |
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* // let a = area->addr |
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* // we reach kasan_populate_vmalloc |
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* // and call kasan_unpoison: |
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* STORE shadow(a), unpoison_val |
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* ... |
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* STORE shadow(a+99), unpoison_val x = LOAD p |
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* // rest of vmalloc process <data dependency> |
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* STORE p, a LOAD shadow(x+99) |
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* |
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* If there is no barrier between the end of unpoisoning the shadow |
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* and the store of the result to p, the stores could be committed |
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* in a different order by CPU#0, and CPU#1 could erroneously observe |
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* poison in the shadow. |
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* |
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* We need some sort of barrier between the stores. |
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* |
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* In the vmalloc() case, this is provided by a smp_wmb() in |
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* clear_vm_uninitialized_flag(). In the per-cpu allocator and in |
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* get_vm_area() and friends, the caller gets shadow allocated but |
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* doesn't have any pages mapped into the virtual address space that |
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* has been reserved. Mapping those pages in will involve taking and |
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* releasing a page-table lock, which will provide the barrier. |
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*/ |
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return 0; |
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} |
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/* |
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* Poison the shadow for a vmalloc region. Called as part of the |
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* freeing process at the time the region is freed. |
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*/ |
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void kasan_poison_vmalloc(const void *start, unsigned long size) |
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{ |
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if (!is_vmalloc_or_module_addr(start)) |
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return; |
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size = round_up(size, KASAN_GRANULE_SIZE); |
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kasan_poison(start, size, KASAN_VMALLOC_INVALID, false); |
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} |
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void kasan_unpoison_vmalloc(const void *start, unsigned long size) |
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{ |
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if (!is_vmalloc_or_module_addr(start)) |
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return; |
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kasan_unpoison(start, size, false); |
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} |
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static int kasan_depopulate_vmalloc_pte(pte_t *ptep, unsigned long addr, |
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void *unused) |
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{ |
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unsigned long page; |
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page = (unsigned long)__va(pte_pfn(*ptep) << PAGE_SHIFT); |
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spin_lock(&init_mm.page_table_lock); |
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if (likely(!pte_none(*ptep))) { |
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pte_clear(&init_mm, addr, ptep); |
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free_page(page); |
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} |
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spin_unlock(&init_mm.page_table_lock); |
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return 0; |
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} |
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/* |
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* Release the backing for the vmalloc region [start, end), which |
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* lies within the free region [free_region_start, free_region_end). |
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* |
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* This can be run lazily, long after the region was freed. It runs |
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* under vmap_area_lock, so it's not safe to interact with the vmalloc/vmap |
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* infrastructure. |
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* |
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* How does this work? |
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* ------------------- |
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* |
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* We have a region that is page aligned, labeled as A. |
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* That might not map onto the shadow in a way that is page-aligned: |
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* |
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* start end |
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* v v |
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* |????????|????????|AAAAAAAA|AA....AA|AAAAAAAA|????????| < vmalloc |
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* -------- -------- -------- -------- -------- |
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* | | | | | |
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* | | | /-------/ | |
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* \-------\|/------/ |/---------------/ |
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* ||| || |
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* |??AAAAAA|AAAAAAAA|AA??????| < shadow |
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* (1) (2) (3) |
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* |
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* First we align the start upwards and the end downwards, so that the |
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* shadow of the region aligns with shadow page boundaries. In the |
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* example, this gives us the shadow page (2). This is the shadow entirely |
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* covered by this allocation. |
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* |
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* Then we have the tricky bits. We want to know if we can free the |
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* partially covered shadow pages - (1) and (3) in the example. For this, |
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* we are given the start and end of the free region that contains this |
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* allocation. Extending our previous example, we could have: |
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* |
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* free_region_start free_region_end |
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* | start end | |
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* v v v v |
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* |FFFFFFFF|FFFFFFFF|AAAAAAAA|AA....AA|AAAAAAAA|FFFFFFFF| < vmalloc |
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* -------- -------- -------- -------- -------- |
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* | | | | | |
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* | | | /-------/ | |
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* \-------\|/------/ |/---------------/ |
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* ||| || |
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* |FFAAAAAA|AAAAAAAA|AAF?????| < shadow |
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* (1) (2) (3) |
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* |
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* Once again, we align the start of the free region up, and the end of |
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* the free region down so that the shadow is page aligned. So we can free |
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* page (1) - we know no allocation currently uses anything in that page, |
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* because all of it is in the vmalloc free region. But we cannot free |
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* page (3), because we can't be sure that the rest of it is unused. |
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* |
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* We only consider pages that contain part of the original region for |
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* freeing: we don't try to free other pages from the free region or we'd |
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* end up trying to free huge chunks of virtual address space. |
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* |
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* Concurrency |
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* ----------- |
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* |
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* How do we know that we're not freeing a page that is simultaneously |
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* being used for a fresh allocation in kasan_populate_vmalloc(_pte)? |
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* |
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* We _can_ have kasan_release_vmalloc and kasan_populate_vmalloc running |
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* at the same time. While we run under free_vmap_area_lock, the population |
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* code does not. |
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* |
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* free_vmap_area_lock instead operates to ensure that the larger range |
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* [free_region_start, free_region_end) is safe: because __alloc_vmap_area and |
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* the per-cpu region-finding algorithm both run under free_vmap_area_lock, |
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* no space identified as free will become used while we are running. This |
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* means that so long as we are careful with alignment and only free shadow |
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* pages entirely covered by the free region, we will not run in to any |
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* trouble - any simultaneous allocations will be for disjoint regions. |
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*/ |
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void kasan_release_vmalloc(unsigned long start, unsigned long end, |
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unsigned long free_region_start, |
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unsigned long free_region_end) |
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{ |
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void *shadow_start, *shadow_end; |
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unsigned long region_start, region_end; |
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unsigned long size; |
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region_start = ALIGN(start, KASAN_MEMORY_PER_SHADOW_PAGE); |
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region_end = ALIGN_DOWN(end, KASAN_MEMORY_PER_SHADOW_PAGE); |
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free_region_start = ALIGN(free_region_start, KASAN_MEMORY_PER_SHADOW_PAGE); |
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if (start != region_start && |
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free_region_start < region_start) |
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region_start -= KASAN_MEMORY_PER_SHADOW_PAGE; |
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free_region_end = ALIGN_DOWN(free_region_end, KASAN_MEMORY_PER_SHADOW_PAGE); |
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if (end != region_end && |
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free_region_end > region_end) |
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region_end += KASAN_MEMORY_PER_SHADOW_PAGE; |
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shadow_start = kasan_mem_to_shadow((void *)region_start); |
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shadow_end = kasan_mem_to_shadow((void *)region_end); |
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if (shadow_end > shadow_start) { |
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size = shadow_end - shadow_start; |
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apply_to_existing_page_range(&init_mm, |
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(unsigned long)shadow_start, |
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size, kasan_depopulate_vmalloc_pte, |
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NULL); |
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flush_tlb_kernel_range((unsigned long)shadow_start, |
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(unsigned long)shadow_end); |
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} |
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} |
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#else /* CONFIG_KASAN_VMALLOC */ |
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int kasan_module_alloc(void *addr, size_t size) |
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{ |
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void *ret; |
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size_t scaled_size; |
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size_t shadow_size; |
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unsigned long shadow_start; |
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shadow_start = (unsigned long)kasan_mem_to_shadow(addr); |
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scaled_size = (size + KASAN_GRANULE_SIZE - 1) >> |
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KASAN_SHADOW_SCALE_SHIFT; |
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shadow_size = round_up(scaled_size, PAGE_SIZE); |
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if (WARN_ON(!PAGE_ALIGNED(shadow_start))) |
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return -EINVAL; |
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ret = __vmalloc_node_range(shadow_size, 1, shadow_start, |
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shadow_start + shadow_size, |
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GFP_KERNEL, |
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PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE, |
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__builtin_return_address(0)); |
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if (ret) { |
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__memset(ret, KASAN_SHADOW_INIT, shadow_size); |
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find_vm_area(addr)->flags |= VM_KASAN; |
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kmemleak_ignore(ret); |
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return 0; |
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} |
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return -ENOMEM; |
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} |
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void kasan_free_shadow(const struct vm_struct *vm) |
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{ |
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if (vm->flags & VM_KASAN) |
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vfree(kasan_mem_to_shadow(vm->addr)); |
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} |
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#endif
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