![Vincenzo Frascino](/assets/img/avatar_default.png)
kasan_unpoison_stack_above_sp_to() is defined in kasan code but never used. The function was introduced as part of the commit: commit9f7d416c36
("kprobes: Unpoison stack in jprobe_return() for KASAN") ... where it was necessary because x86's jprobe_return() would leave stale shadow on the stack, and was an oddity in that regard. Since then, jprobes were removed entirely, and as of commit: commit80006dbee6
("kprobes/x86: Remove jprobe implementation") ... there have been no callers of this function. Remove the declaration and the implementation. Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Mark Rutland <mark.rutland@arm.com> Reviewed-by: Andrey Konovalov <andreyknvl@google.com> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Link: http://lkml.kernel.org/r/20200706143505.23299-1-vincenzo.frascino@arm.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
932 lines
26 KiB
C
932 lines
26 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* This file contains common generic and tag-based KASAN code.
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*
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* Copyright (c) 2014 Samsung Electronics Co., Ltd.
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* Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
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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 <andreyknvl@gmail.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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*/
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#include <linux/export.h>
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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/kmemleak.h>
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#include <linux/linkage.h>
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#include <linux/memblock.h>
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#include <linux/memory.h>
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#include <linux/mm.h>
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#include <linux/module.h>
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#include <linux/printk.h>
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#include <linux/sched.h>
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#include <linux/sched/task_stack.h>
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#include <linux/slab.h>
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#include <linux/stacktrace.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 <linux/bug.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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#include "../slab.h"
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depot_stack_handle_t kasan_save_stack(gfp_t flags)
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{
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unsigned long entries[KASAN_STACK_DEPTH];
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unsigned int nr_entries;
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nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0);
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nr_entries = filter_irq_stacks(entries, nr_entries);
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return stack_depot_save(entries, nr_entries, flags);
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}
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void kasan_set_track(struct kasan_track *track, gfp_t flags)
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{
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track->pid = current->pid;
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track->stack = kasan_save_stack(flags);
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}
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void kasan_enable_current(void)
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{
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current->kasan_depth++;
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}
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void kasan_disable_current(void)
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{
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current->kasan_depth--;
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}
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bool __kasan_check_read(const volatile void *p, unsigned int size)
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{
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return check_memory_region((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 check_memory_region((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 (!check_memory_region((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 (!check_memory_region((unsigned long)src, len, false, _RET_IP_) ||
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!check_memory_region((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 (!check_memory_region((unsigned long)src, len, false, _RET_IP_) ||
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!check_memory_region((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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/*
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* Poisons the shadow memory for 'size' bytes starting from 'addr'.
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* Memory addresses should be aligned to KASAN_SHADOW_SCALE_SIZE.
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*/
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void kasan_poison_shadow(const void *address, size_t size, u8 value)
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{
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void *shadow_start, *shadow_end;
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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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address = reset_tag(address);
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shadow_start = kasan_mem_to_shadow(address);
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shadow_end = kasan_mem_to_shadow(address + size);
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__memset(shadow_start, value, shadow_end - shadow_start);
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}
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void kasan_unpoison_shadow(const void *address, size_t size)
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{
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u8 tag = get_tag(address);
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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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address = reset_tag(address);
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kasan_poison_shadow(address, size, tag);
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if (size & KASAN_SHADOW_MASK) {
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u8 *shadow = (u8 *)kasan_mem_to_shadow(address + size);
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if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
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*shadow = tag;
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else
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*shadow = size & KASAN_SHADOW_MASK;
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}
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}
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static void __kasan_unpoison_stack(struct task_struct *task, const void *sp)
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{
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void *base = task_stack_page(task);
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size_t size = sp - base;
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kasan_unpoison_shadow(base, size);
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}
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/* Unpoison the entire stack for a task. */
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void kasan_unpoison_task_stack(struct task_struct *task)
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{
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__kasan_unpoison_stack(task, task_stack_page(task) + THREAD_SIZE);
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}
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/* Unpoison the stack for the current task beyond a watermark sp value. */
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asmlinkage void kasan_unpoison_task_stack_below(const void *watermark)
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{
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/*
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* Calculate the task stack base address. Avoid using 'current'
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* because this function is called by early resume code which hasn't
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* yet set up the percpu register (%gs).
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*/
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void *base = (void *)((unsigned long)watermark & ~(THREAD_SIZE - 1));
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kasan_unpoison_shadow(base, watermark - base);
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}
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void kasan_alloc_pages(struct page *page, unsigned int order)
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{
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u8 tag;
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unsigned long i;
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if (unlikely(PageHighMem(page)))
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return;
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tag = random_tag();
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for (i = 0; i < (1 << order); i++)
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page_kasan_tag_set(page + i, tag);
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kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order);
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}
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void kasan_free_pages(struct page *page, unsigned int order)
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{
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if (likely(!PageHighMem(page)))
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kasan_poison_shadow(page_address(page),
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PAGE_SIZE << order,
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KASAN_FREE_PAGE);
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}
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/*
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* Adaptive redzone policy taken from the userspace AddressSanitizer runtime.
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* For larger allocations larger redzones are used.
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*/
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static inline unsigned int optimal_redzone(unsigned int object_size)
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{
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if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
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return 0;
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return
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object_size <= 64 - 16 ? 16 :
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object_size <= 128 - 32 ? 32 :
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object_size <= 512 - 64 ? 64 :
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object_size <= 4096 - 128 ? 128 :
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object_size <= (1 << 14) - 256 ? 256 :
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object_size <= (1 << 15) - 512 ? 512 :
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object_size <= (1 << 16) - 1024 ? 1024 : 2048;
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}
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void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
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slab_flags_t *flags)
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{
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unsigned int orig_size = *size;
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unsigned int redzone_size;
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int redzone_adjust;
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/* Add alloc meta. */
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cache->kasan_info.alloc_meta_offset = *size;
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*size += sizeof(struct kasan_alloc_meta);
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/* Add free meta. */
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if (IS_ENABLED(CONFIG_KASAN_GENERIC) &&
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(cache->flags & SLAB_TYPESAFE_BY_RCU || cache->ctor ||
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cache->object_size < sizeof(struct kasan_free_meta))) {
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cache->kasan_info.free_meta_offset = *size;
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*size += sizeof(struct kasan_free_meta);
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}
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redzone_size = optimal_redzone(cache->object_size);
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redzone_adjust = redzone_size - (*size - cache->object_size);
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if (redzone_adjust > 0)
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*size += redzone_adjust;
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*size = min_t(unsigned int, KMALLOC_MAX_SIZE,
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max(*size, cache->object_size + redzone_size));
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/*
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* If the metadata doesn't fit, don't enable KASAN at all.
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*/
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if (*size <= cache->kasan_info.alloc_meta_offset ||
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*size <= cache->kasan_info.free_meta_offset) {
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cache->kasan_info.alloc_meta_offset = 0;
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cache->kasan_info.free_meta_offset = 0;
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*size = orig_size;
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return;
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}
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*flags |= SLAB_KASAN;
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}
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size_t kasan_metadata_size(struct kmem_cache *cache)
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{
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return (cache->kasan_info.alloc_meta_offset ?
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sizeof(struct kasan_alloc_meta) : 0) +
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(cache->kasan_info.free_meta_offset ?
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sizeof(struct kasan_free_meta) : 0);
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}
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struct kasan_alloc_meta *get_alloc_info(struct kmem_cache *cache,
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const void *object)
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{
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return (void *)object + cache->kasan_info.alloc_meta_offset;
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}
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struct kasan_free_meta *get_free_info(struct kmem_cache *cache,
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const void *object)
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{
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BUILD_BUG_ON(sizeof(struct kasan_free_meta) > 32);
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return (void *)object + cache->kasan_info.free_meta_offset;
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}
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void kasan_poison_slab(struct page *page)
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{
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unsigned long i;
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for (i = 0; i < compound_nr(page); i++)
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page_kasan_tag_reset(page + i);
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kasan_poison_shadow(page_address(page), page_size(page),
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KASAN_KMALLOC_REDZONE);
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}
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void kasan_unpoison_object_data(struct kmem_cache *cache, void *object)
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{
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kasan_unpoison_shadow(object, cache->object_size);
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}
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void kasan_poison_object_data(struct kmem_cache *cache, void *object)
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{
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kasan_poison_shadow(object,
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round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE),
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KASAN_KMALLOC_REDZONE);
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}
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/*
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* This function assigns a tag to an object considering the following:
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* 1. A cache might have a constructor, which might save a pointer to a slab
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* object somewhere (e.g. in the object itself). We preassign a tag for
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* each object in caches with constructors during slab creation and reuse
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* the same tag each time a particular object is allocated.
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* 2. A cache might be SLAB_TYPESAFE_BY_RCU, which means objects can be
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* accessed after being freed. We preassign tags for objects in these
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* caches as well.
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* 3. For SLAB allocator we can't preassign tags randomly since the freelist
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* is stored as an array of indexes instead of a linked list. Assign tags
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* based on objects indexes, so that objects that are next to each other
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* get different tags.
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*/
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static u8 assign_tag(struct kmem_cache *cache, const void *object,
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bool init, bool keep_tag)
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{
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/*
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* 1. When an object is kmalloc()'ed, two hooks are called:
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* kasan_slab_alloc() and kasan_kmalloc(). We assign the
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* tag only in the first one.
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* 2. We reuse the same tag for krealloc'ed objects.
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*/
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if (keep_tag)
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return get_tag(object);
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/*
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* If the cache neither has a constructor nor has SLAB_TYPESAFE_BY_RCU
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* set, assign a tag when the object is being allocated (init == false).
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*/
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if (!cache->ctor && !(cache->flags & SLAB_TYPESAFE_BY_RCU))
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return init ? KASAN_TAG_KERNEL : random_tag();
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/* For caches that either have a constructor or SLAB_TYPESAFE_BY_RCU: */
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#ifdef CONFIG_SLAB
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/* For SLAB assign tags based on the object index in the freelist. */
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return (u8)obj_to_index(cache, virt_to_page(object), (void *)object);
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#else
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/*
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* For SLUB assign a random tag during slab creation, otherwise reuse
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* the already assigned tag.
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*/
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return init ? random_tag() : get_tag(object);
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#endif
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}
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void * __must_check kasan_init_slab_obj(struct kmem_cache *cache,
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const void *object)
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{
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struct kasan_alloc_meta *alloc_info;
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if (!(cache->flags & SLAB_KASAN))
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return (void *)object;
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alloc_info = get_alloc_info(cache, object);
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__memset(alloc_info, 0, sizeof(*alloc_info));
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if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
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object = set_tag(object,
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assign_tag(cache, object, true, false));
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return (void *)object;
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}
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static inline bool shadow_invalid(u8 tag, s8 shadow_byte)
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{
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if (IS_ENABLED(CONFIG_KASAN_GENERIC))
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return shadow_byte < 0 ||
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shadow_byte >= KASAN_SHADOW_SCALE_SIZE;
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/* else CONFIG_KASAN_SW_TAGS: */
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if ((u8)shadow_byte == KASAN_TAG_INVALID)
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return true;
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if ((tag != KASAN_TAG_KERNEL) && (tag != (u8)shadow_byte))
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return true;
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return false;
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}
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static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
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unsigned long ip, bool quarantine)
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{
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s8 shadow_byte;
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u8 tag;
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void *tagged_object;
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unsigned long rounded_up_size;
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tag = get_tag(object);
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tagged_object = object;
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object = reset_tag(object);
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if (unlikely(nearest_obj(cache, virt_to_head_page(object), object) !=
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object)) {
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kasan_report_invalid_free(tagged_object, ip);
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return true;
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}
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/* RCU slabs could be legally used after free within the RCU period */
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if (unlikely(cache->flags & SLAB_TYPESAFE_BY_RCU))
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return false;
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shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(object));
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if (shadow_invalid(tag, shadow_byte)) {
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kasan_report_invalid_free(tagged_object, ip);
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return true;
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}
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rounded_up_size = round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE);
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kasan_poison_shadow(object, rounded_up_size, KASAN_KMALLOC_FREE);
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if ((IS_ENABLED(CONFIG_KASAN_GENERIC) && !quarantine) ||
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unlikely(!(cache->flags & SLAB_KASAN)))
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return false;
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kasan_set_free_info(cache, object, tag);
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quarantine_put(get_free_info(cache, object), cache);
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return IS_ENABLED(CONFIG_KASAN_GENERIC);
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}
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bool kasan_slab_free(struct kmem_cache *cache, void *object, unsigned long ip)
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{
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return __kasan_slab_free(cache, object, ip, true);
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}
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static void *__kasan_kmalloc(struct kmem_cache *cache, const void *object,
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size_t size, gfp_t flags, bool keep_tag)
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{
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unsigned long redzone_start;
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unsigned long redzone_end;
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u8 tag = 0xff;
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if (gfpflags_allow_blocking(flags))
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quarantine_reduce();
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if (unlikely(object == NULL))
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return NULL;
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redzone_start = round_up((unsigned long)(object + size),
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KASAN_SHADOW_SCALE_SIZE);
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redzone_end = round_up((unsigned long)object + cache->object_size,
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KASAN_SHADOW_SCALE_SIZE);
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if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
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tag = assign_tag(cache, object, false, keep_tag);
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/* Tag is ignored in set_tag without CONFIG_KASAN_SW_TAGS */
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kasan_unpoison_shadow(set_tag(object, tag), size);
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kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
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KASAN_KMALLOC_REDZONE);
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if (cache->flags & SLAB_KASAN)
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kasan_set_track(&get_alloc_info(cache, object)->alloc_track, flags);
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return set_tag(object, tag);
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}
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void * __must_check kasan_slab_alloc(struct kmem_cache *cache, void *object,
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gfp_t flags)
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{
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return __kasan_kmalloc(cache, object, cache->object_size, flags, false);
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}
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void * __must_check kasan_kmalloc(struct kmem_cache *cache, const void *object,
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size_t size, gfp_t flags)
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{
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return __kasan_kmalloc(cache, object, size, flags, true);
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}
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EXPORT_SYMBOL(kasan_kmalloc);
|
|
|
|
void * __must_check kasan_kmalloc_large(const void *ptr, size_t size,
|
|
gfp_t flags)
|
|
{
|
|
struct page *page;
|
|
unsigned long redzone_start;
|
|
unsigned long redzone_end;
|
|
|
|
if (gfpflags_allow_blocking(flags))
|
|
quarantine_reduce();
|
|
|
|
if (unlikely(ptr == NULL))
|
|
return NULL;
|
|
|
|
page = virt_to_page(ptr);
|
|
redzone_start = round_up((unsigned long)(ptr + size),
|
|
KASAN_SHADOW_SCALE_SIZE);
|
|
redzone_end = (unsigned long)ptr + page_size(page);
|
|
|
|
kasan_unpoison_shadow(ptr, size);
|
|
kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
|
|
KASAN_PAGE_REDZONE);
|
|
|
|
return (void *)ptr;
|
|
}
|
|
|
|
void * __must_check kasan_krealloc(const void *object, size_t size, gfp_t flags)
|
|
{
|
|
struct page *page;
|
|
|
|
if (unlikely(object == ZERO_SIZE_PTR))
|
|
return (void *)object;
|
|
|
|
page = virt_to_head_page(object);
|
|
|
|
if (unlikely(!PageSlab(page)))
|
|
return kasan_kmalloc_large(object, size, flags);
|
|
else
|
|
return __kasan_kmalloc(page->slab_cache, object, size,
|
|
flags, true);
|
|
}
|
|
|
|
void kasan_poison_kfree(void *ptr, unsigned long ip)
|
|
{
|
|
struct page *page;
|
|
|
|
page = virt_to_head_page(ptr);
|
|
|
|
if (unlikely(!PageSlab(page))) {
|
|
if (ptr != page_address(page)) {
|
|
kasan_report_invalid_free(ptr, ip);
|
|
return;
|
|
}
|
|
kasan_poison_shadow(ptr, page_size(page), KASAN_FREE_PAGE);
|
|
} else {
|
|
__kasan_slab_free(page->slab_cache, ptr, ip, false);
|
|
}
|
|
}
|
|
|
|
void kasan_kfree_large(void *ptr, unsigned long ip)
|
|
{
|
|
if (ptr != page_address(virt_to_head_page(ptr)))
|
|
kasan_report_invalid_free(ptr, ip);
|
|
/* The object will be poisoned by page_alloc. */
|
|
}
|
|
|
|
#ifndef CONFIG_KASAN_VMALLOC
|
|
int kasan_module_alloc(void *addr, size_t size)
|
|
{
|
|
void *ret;
|
|
size_t scaled_size;
|
|
size_t shadow_size;
|
|
unsigned long shadow_start;
|
|
|
|
shadow_start = (unsigned long)kasan_mem_to_shadow(addr);
|
|
scaled_size = (size + KASAN_SHADOW_MASK) >> KASAN_SHADOW_SCALE_SHIFT;
|
|
shadow_size = round_up(scaled_size, PAGE_SIZE);
|
|
|
|
if (WARN_ON(!PAGE_ALIGNED(shadow_start)))
|
|
return -EINVAL;
|
|
|
|
ret = __vmalloc_node_range(shadow_size, 1, shadow_start,
|
|
shadow_start + shadow_size,
|
|
GFP_KERNEL,
|
|
PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE,
|
|
__builtin_return_address(0));
|
|
|
|
if (ret) {
|
|
__memset(ret, KASAN_SHADOW_INIT, shadow_size);
|
|
find_vm_area(addr)->flags |= VM_KASAN;
|
|
kmemleak_ignore(ret);
|
|
return 0;
|
|
}
|
|
|
|
return -ENOMEM;
|
|
}
|
|
|
|
void kasan_free_shadow(const struct vm_struct *vm)
|
|
{
|
|
if (vm->flags & VM_KASAN)
|
|
vfree(kasan_mem_to_shadow(vm->addr));
|
|
}
|
|
#endif
|
|
|
|
#ifdef CONFIG_MEMORY_HOTPLUG
|
|
static bool shadow_mapped(unsigned long addr)
|
|
{
|
|
pgd_t *pgd = pgd_offset_k(addr);
|
|
p4d_t *p4d;
|
|
pud_t *pud;
|
|
pmd_t *pmd;
|
|
pte_t *pte;
|
|
|
|
if (pgd_none(*pgd))
|
|
return false;
|
|
p4d = p4d_offset(pgd, addr);
|
|
if (p4d_none(*p4d))
|
|
return false;
|
|
pud = pud_offset(p4d, addr);
|
|
if (pud_none(*pud))
|
|
return false;
|
|
|
|
/*
|
|
* We can't use pud_large() or pud_huge(), the first one is
|
|
* arch-specific, the last one depends on HUGETLB_PAGE. So let's abuse
|
|
* pud_bad(), if pud is bad then it's bad because it's huge.
|
|
*/
|
|
if (pud_bad(*pud))
|
|
return true;
|
|
pmd = pmd_offset(pud, addr);
|
|
if (pmd_none(*pmd))
|
|
return false;
|
|
|
|
if (pmd_bad(*pmd))
|
|
return true;
|
|
pte = pte_offset_kernel(pmd, addr);
|
|
return !pte_none(*pte);
|
|
}
|
|
|
|
static int __meminit kasan_mem_notifier(struct notifier_block *nb,
|
|
unsigned long action, void *data)
|
|
{
|
|
struct memory_notify *mem_data = data;
|
|
unsigned long nr_shadow_pages, start_kaddr, shadow_start;
|
|
unsigned long shadow_end, shadow_size;
|
|
|
|
nr_shadow_pages = mem_data->nr_pages >> KASAN_SHADOW_SCALE_SHIFT;
|
|
start_kaddr = (unsigned long)pfn_to_kaddr(mem_data->start_pfn);
|
|
shadow_start = (unsigned long)kasan_mem_to_shadow((void *)start_kaddr);
|
|
shadow_size = nr_shadow_pages << PAGE_SHIFT;
|
|
shadow_end = shadow_start + shadow_size;
|
|
|
|
if (WARN_ON(mem_data->nr_pages % KASAN_SHADOW_SCALE_SIZE) ||
|
|
WARN_ON(start_kaddr % (KASAN_SHADOW_SCALE_SIZE << PAGE_SHIFT)))
|
|
return NOTIFY_BAD;
|
|
|
|
switch (action) {
|
|
case MEM_GOING_ONLINE: {
|
|
void *ret;
|
|
|
|
/*
|
|
* If shadow is mapped already than it must have been mapped
|
|
* during the boot. This could happen if we onlining previously
|
|
* offlined memory.
|
|
*/
|
|
if (shadow_mapped(shadow_start))
|
|
return NOTIFY_OK;
|
|
|
|
ret = __vmalloc_node_range(shadow_size, PAGE_SIZE, shadow_start,
|
|
shadow_end, GFP_KERNEL,
|
|
PAGE_KERNEL, VM_NO_GUARD,
|
|
pfn_to_nid(mem_data->start_pfn),
|
|
__builtin_return_address(0));
|
|
if (!ret)
|
|
return NOTIFY_BAD;
|
|
|
|
kmemleak_ignore(ret);
|
|
return NOTIFY_OK;
|
|
}
|
|
case MEM_CANCEL_ONLINE:
|
|
case MEM_OFFLINE: {
|
|
struct vm_struct *vm;
|
|
|
|
/*
|
|
* shadow_start was either mapped during boot by kasan_init()
|
|
* or during memory online by __vmalloc_node_range().
|
|
* In the latter case we can use vfree() to free shadow.
|
|
* Non-NULL result of the find_vm_area() will tell us if
|
|
* that was the second case.
|
|
*
|
|
* Currently it's not possible to free shadow mapped
|
|
* during boot by kasan_init(). It's because the code
|
|
* to do that hasn't been written yet. So we'll just
|
|
* leak the memory.
|
|
*/
|
|
vm = find_vm_area((void *)shadow_start);
|
|
if (vm)
|
|
vfree((void *)shadow_start);
|
|
}
|
|
}
|
|
|
|
return NOTIFY_OK;
|
|
}
|
|
|
|
static int __init kasan_memhotplug_init(void)
|
|
{
|
|
hotplug_memory_notifier(kasan_mem_notifier, 0);
|
|
|
|
return 0;
|
|
}
|
|
|
|
core_initcall(kasan_memhotplug_init);
|
|
#endif
|
|
|
|
#ifdef CONFIG_KASAN_VMALLOC
|
|
static int kasan_populate_vmalloc_pte(pte_t *ptep, unsigned long addr,
|
|
void *unused)
|
|
{
|
|
unsigned long page;
|
|
pte_t pte;
|
|
|
|
if (likely(!pte_none(*ptep)))
|
|
return 0;
|
|
|
|
page = __get_free_page(GFP_KERNEL);
|
|
if (!page)
|
|
return -ENOMEM;
|
|
|
|
memset((void *)page, KASAN_VMALLOC_INVALID, PAGE_SIZE);
|
|
pte = pfn_pte(PFN_DOWN(__pa(page)), PAGE_KERNEL);
|
|
|
|
spin_lock(&init_mm.page_table_lock);
|
|
if (likely(pte_none(*ptep))) {
|
|
set_pte_at(&init_mm, addr, ptep, pte);
|
|
page = 0;
|
|
}
|
|
spin_unlock(&init_mm.page_table_lock);
|
|
if (page)
|
|
free_page(page);
|
|
return 0;
|
|
}
|
|
|
|
int kasan_populate_vmalloc(unsigned long addr, unsigned long size)
|
|
{
|
|
unsigned long shadow_start, shadow_end;
|
|
int ret;
|
|
|
|
if (!is_vmalloc_or_module_addr((void *)addr))
|
|
return 0;
|
|
|
|
shadow_start = (unsigned long)kasan_mem_to_shadow((void *)addr);
|
|
shadow_start = ALIGN_DOWN(shadow_start, PAGE_SIZE);
|
|
shadow_end = (unsigned long)kasan_mem_to_shadow((void *)addr + size);
|
|
shadow_end = ALIGN(shadow_end, PAGE_SIZE);
|
|
|
|
ret = apply_to_page_range(&init_mm, shadow_start,
|
|
shadow_end - shadow_start,
|
|
kasan_populate_vmalloc_pte, NULL);
|
|
if (ret)
|
|
return ret;
|
|
|
|
flush_cache_vmap(shadow_start, shadow_end);
|
|
|
|
/*
|
|
* We need to be careful about inter-cpu effects here. Consider:
|
|
*
|
|
* CPU#0 CPU#1
|
|
* WRITE_ONCE(p, vmalloc(100)); while (x = READ_ONCE(p)) ;
|
|
* p[99] = 1;
|
|
*
|
|
* With compiler instrumentation, that ends up looking like this:
|
|
*
|
|
* CPU#0 CPU#1
|
|
* // vmalloc() allocates memory
|
|
* // let a = area->addr
|
|
* // we reach kasan_populate_vmalloc
|
|
* // and call kasan_unpoison_shadow:
|
|
* STORE shadow(a), unpoison_val
|
|
* ...
|
|
* STORE shadow(a+99), unpoison_val x = LOAD p
|
|
* // rest of vmalloc process <data dependency>
|
|
* STORE p, a LOAD shadow(x+99)
|
|
*
|
|
* If there is no barrier between the end of unpoisioning the shadow
|
|
* and the store of the result to p, the stores could be committed
|
|
* in a different order by CPU#0, and CPU#1 could erroneously observe
|
|
* poison in the shadow.
|
|
*
|
|
* We need some sort of barrier between the stores.
|
|
*
|
|
* In the vmalloc() case, this is provided by a smp_wmb() in
|
|
* clear_vm_uninitialized_flag(). In the per-cpu allocator and in
|
|
* get_vm_area() and friends, the caller gets shadow allocated but
|
|
* doesn't have any pages mapped into the virtual address space that
|
|
* has been reserved. Mapping those pages in will involve taking and
|
|
* releasing a page-table lock, which will provide the barrier.
|
|
*/
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Poison the shadow for a vmalloc region. Called as part of the
|
|
* freeing process at the time the region is freed.
|
|
*/
|
|
void kasan_poison_vmalloc(const void *start, unsigned long size)
|
|
{
|
|
if (!is_vmalloc_or_module_addr(start))
|
|
return;
|
|
|
|
size = round_up(size, KASAN_SHADOW_SCALE_SIZE);
|
|
kasan_poison_shadow(start, size, KASAN_VMALLOC_INVALID);
|
|
}
|
|
|
|
void kasan_unpoison_vmalloc(const void *start, unsigned long size)
|
|
{
|
|
if (!is_vmalloc_or_module_addr(start))
|
|
return;
|
|
|
|
kasan_unpoison_shadow(start, size);
|
|
}
|
|
|
|
static int kasan_depopulate_vmalloc_pte(pte_t *ptep, unsigned long addr,
|
|
void *unused)
|
|
{
|
|
unsigned long page;
|
|
|
|
page = (unsigned long)__va(pte_pfn(*ptep) << PAGE_SHIFT);
|
|
|
|
spin_lock(&init_mm.page_table_lock);
|
|
|
|
if (likely(!pte_none(*ptep))) {
|
|
pte_clear(&init_mm, addr, ptep);
|
|
free_page(page);
|
|
}
|
|
spin_unlock(&init_mm.page_table_lock);
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Release the backing for the vmalloc region [start, end), which
|
|
* lies within the free region [free_region_start, free_region_end).
|
|
*
|
|
* This can be run lazily, long after the region was freed. It runs
|
|
* under vmap_area_lock, so it's not safe to interact with the vmalloc/vmap
|
|
* infrastructure.
|
|
*
|
|
* How does this work?
|
|
* -------------------
|
|
*
|
|
* We have a region that is page aligned, labelled as A.
|
|
* That might not map onto the shadow in a way that is page-aligned:
|
|
*
|
|
* start end
|
|
* v v
|
|
* |????????|????????|AAAAAAAA|AA....AA|AAAAAAAA|????????| < vmalloc
|
|
* -------- -------- -------- -------- --------
|
|
* | | | | |
|
|
* | | | /-------/ |
|
|
* \-------\|/------/ |/---------------/
|
|
* ||| ||
|
|
* |??AAAAAA|AAAAAAAA|AA??????| < shadow
|
|
* (1) (2) (3)
|
|
*
|
|
* First we align the start upwards and the end downwards, so that the
|
|
* shadow of the region aligns with shadow page boundaries. In the
|
|
* example, this gives us the shadow page (2). This is the shadow entirely
|
|
* covered by this allocation.
|
|
*
|
|
* Then we have the tricky bits. We want to know if we can free the
|
|
* partially covered shadow pages - (1) and (3) in the example. For this,
|
|
* we are given the start and end of the free region that contains this
|
|
* allocation. Extending our previous example, we could have:
|
|
*
|
|
* free_region_start free_region_end
|
|
* | start end |
|
|
* v v v v
|
|
* |FFFFFFFF|FFFFFFFF|AAAAAAAA|AA....AA|AAAAAAAA|FFFFFFFF| < vmalloc
|
|
* -------- -------- -------- -------- --------
|
|
* | | | | |
|
|
* | | | /-------/ |
|
|
* \-------\|/------/ |/---------------/
|
|
* ||| ||
|
|
* |FFAAAAAA|AAAAAAAA|AAF?????| < shadow
|
|
* (1) (2) (3)
|
|
*
|
|
* Once again, we align the start of the free region up, and the end of
|
|
* the free region down so that the shadow is page aligned. So we can free
|
|
* page (1) - we know no allocation currently uses anything in that page,
|
|
* because all of it is in the vmalloc free region. But we cannot free
|
|
* page (3), because we can't be sure that the rest of it is unused.
|
|
*
|
|
* We only consider pages that contain part of the original region for
|
|
* freeing: we don't try to free other pages from the free region or we'd
|
|
* end up trying to free huge chunks of virtual address space.
|
|
*
|
|
* Concurrency
|
|
* -----------
|
|
*
|
|
* How do we know that we're not freeing a page that is simultaneously
|
|
* being used for a fresh allocation in kasan_populate_vmalloc(_pte)?
|
|
*
|
|
* We _can_ have kasan_release_vmalloc and kasan_populate_vmalloc running
|
|
* at the same time. While we run under free_vmap_area_lock, the population
|
|
* code does not.
|
|
*
|
|
* free_vmap_area_lock instead operates to ensure that the larger range
|
|
* [free_region_start, free_region_end) is safe: because __alloc_vmap_area and
|
|
* the per-cpu region-finding algorithm both run under free_vmap_area_lock,
|
|
* no space identified as free will become used while we are running. This
|
|
* means that so long as we are careful with alignment and only free shadow
|
|
* pages entirely covered by the free region, we will not run in to any
|
|
* trouble - any simultaneous allocations will be for disjoint regions.
|
|
*/
|
|
void kasan_release_vmalloc(unsigned long start, unsigned long end,
|
|
unsigned long free_region_start,
|
|
unsigned long free_region_end)
|
|
{
|
|
void *shadow_start, *shadow_end;
|
|
unsigned long region_start, region_end;
|
|
unsigned long size;
|
|
|
|
region_start = ALIGN(start, PAGE_SIZE * KASAN_SHADOW_SCALE_SIZE);
|
|
region_end = ALIGN_DOWN(end, PAGE_SIZE * KASAN_SHADOW_SCALE_SIZE);
|
|
|
|
free_region_start = ALIGN(free_region_start,
|
|
PAGE_SIZE * KASAN_SHADOW_SCALE_SIZE);
|
|
|
|
if (start != region_start &&
|
|
free_region_start < region_start)
|
|
region_start -= PAGE_SIZE * KASAN_SHADOW_SCALE_SIZE;
|
|
|
|
free_region_end = ALIGN_DOWN(free_region_end,
|
|
PAGE_SIZE * KASAN_SHADOW_SCALE_SIZE);
|
|
|
|
if (end != region_end &&
|
|
free_region_end > region_end)
|
|
region_end += PAGE_SIZE * KASAN_SHADOW_SCALE_SIZE;
|
|
|
|
shadow_start = kasan_mem_to_shadow((void *)region_start);
|
|
shadow_end = kasan_mem_to_shadow((void *)region_end);
|
|
|
|
if (shadow_end > shadow_start) {
|
|
size = shadow_end - shadow_start;
|
|
apply_to_existing_page_range(&init_mm,
|
|
(unsigned long)shadow_start,
|
|
size, kasan_depopulate_vmalloc_pte,
|
|
NULL);
|
|
flush_tlb_kernel_range((unsigned long)shadow_start,
|
|
(unsigned long)shadow_end);
|
|
}
|
|
}
|
|
#endif
|