lkml.org 
[lkml]   [2020]   [Nov]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    Subject[PATCH v9 09/44] kasan: split out shadow.c from common.c
    From
    This is a preparatory commit for the upcoming addition of a new hardware
    tag-based (MTE-based) KASAN mode.

    The new mode won't be using shadow memory. Move all shadow-related code
    to shadow.c, which is only enabled for software KASAN modes that use
    shadow memory.

    No functional changes for software modes.

    Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
    Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
    Reviewed-by: Marco Elver <elver@google.com>
    ---
    Change-Id: Ic1c32ce72d4649848e9e6a1f2c8dd269c77673f2
    ---
    mm/kasan/Makefile | 6 +-
    mm/kasan/common.c | 486 +-------------------------------------------
    mm/kasan/shadow.c | 505 ++++++++++++++++++++++++++++++++++++++++++++++
    3 files changed, 510 insertions(+), 487 deletions(-)
    create mode 100644 mm/kasan/shadow.c

    diff --git a/mm/kasan/Makefile b/mm/kasan/Makefile
    index 7cf685bb51bd..7cc1031e1ef8 100644
    --- a/mm/kasan/Makefile
    +++ b/mm/kasan/Makefile
    @@ -10,6 +10,7 @@ CFLAGS_REMOVE_generic_report.o = $(CC_FLAGS_FTRACE)
    CFLAGS_REMOVE_init.o = $(CC_FLAGS_FTRACE)
    CFLAGS_REMOVE_quarantine.o = $(CC_FLAGS_FTRACE)
    CFLAGS_REMOVE_report.o = $(CC_FLAGS_FTRACE)
    +CFLAGS_REMOVE_shadow.o = $(CC_FLAGS_FTRACE)
    CFLAGS_REMOVE_tags.o = $(CC_FLAGS_FTRACE)
    CFLAGS_REMOVE_tags_report.o = $(CC_FLAGS_FTRACE)

    @@ -26,9 +27,10 @@ CFLAGS_generic_report.o := $(CC_FLAGS_KASAN_RUNTIME)
    CFLAGS_init.o := $(CC_FLAGS_KASAN_RUNTIME)
    CFLAGS_quarantine.o := $(CC_FLAGS_KASAN_RUNTIME)
    CFLAGS_report.o := $(CC_FLAGS_KASAN_RUNTIME)
    +CFLAGS_shadow.o := $(CC_FLAGS_KASAN_RUNTIME)
    CFLAGS_tags.o := $(CC_FLAGS_KASAN_RUNTIME)
    CFLAGS_tags_report.o := $(CC_FLAGS_KASAN_RUNTIME)

    obj-$(CONFIG_KASAN) := common.o report.o
    -obj-$(CONFIG_KASAN_GENERIC) += init.o generic.o generic_report.o quarantine.o
    -obj-$(CONFIG_KASAN_SW_TAGS) += init.o tags.o tags_report.o
    +obj-$(CONFIG_KASAN_GENERIC) += init.o generic.o generic_report.o shadow.o quarantine.o
    +obj-$(CONFIG_KASAN_SW_TAGS) += init.o shadow.o tags.o tags_report.o
    diff --git a/mm/kasan/common.c b/mm/kasan/common.c
    index f65c9f792f8f..123abfb760d4 100644
    --- a/mm/kasan/common.c
    +++ b/mm/kasan/common.c
    @@ -1,6 +1,6 @@
    // SPDX-License-Identifier: GPL-2.0
    /*
    - * This file contains common generic and tag-based KASAN code.
    + * This file contains common KASAN code.
    *
    * Copyright (c) 2014 Samsung Electronics Co., Ltd.
    * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
    @@ -13,7 +13,6 @@
    #include <linux/init.h>
    #include <linux/kasan.h>
    #include <linux/kernel.h>
    -#include <linux/kmemleak.h>
    #include <linux/linkage.h>
    #include <linux/memblock.h>
    #include <linux/memory.h>
    @@ -26,12 +25,8 @@
    #include <linux/stacktrace.h>
    #include <linux/string.h>
    #include <linux/types.h>
    -#include <linux/vmalloc.h>
    #include <linux/bug.h>

    -#include <asm/cacheflush.h>
    -#include <asm/tlbflush.h>
    -
    #include "kasan.h"
    #include "../slab.h"

    @@ -61,93 +56,6 @@ void kasan_disable_current(void)
    current->kasan_depth--;
    }

    -bool __kasan_check_read(const volatile void *p, unsigned int size)
    -{
    - return check_memory_region((unsigned long)p, size, false, _RET_IP_);
    -}
    -EXPORT_SYMBOL(__kasan_check_read);
    -
    -bool __kasan_check_write(const volatile void *p, unsigned int size)
    -{
    - return check_memory_region((unsigned long)p, size, true, _RET_IP_);
    -}
    -EXPORT_SYMBOL(__kasan_check_write);
    -
    -#undef memset
    -void *memset(void *addr, int c, size_t len)
    -{
    - if (!check_memory_region((unsigned long)addr, len, true, _RET_IP_))
    - return NULL;
    -
    - return __memset(addr, c, len);
    -}
    -
    -#ifdef __HAVE_ARCH_MEMMOVE
    -#undef memmove
    -void *memmove(void *dest, const void *src, size_t len)
    -{
    - if (!check_memory_region((unsigned long)src, len, false, _RET_IP_) ||
    - !check_memory_region((unsigned long)dest, len, true, _RET_IP_))
    - return NULL;
    -
    - return __memmove(dest, src, len);
    -}
    -#endif
    -
    -#undef memcpy
    -void *memcpy(void *dest, const void *src, size_t len)
    -{
    - if (!check_memory_region((unsigned long)src, len, false, _RET_IP_) ||
    - !check_memory_region((unsigned long)dest, len, true, _RET_IP_))
    - return NULL;
    -
    - return __memcpy(dest, src, len);
    -}
    -
    -/*
    - * Poisons the shadow memory for 'size' bytes starting from 'addr'.
    - * Memory addresses should be aligned to KASAN_GRANULE_SIZE.
    - */
    -void kasan_poison_memory(const void *address, size_t size, u8 value)
    -{
    - void *shadow_start, *shadow_end;
    -
    - /*
    - * Perform shadow offset calculation based on untagged address, as
    - * some of the callers (e.g. kasan_poison_object_data) pass tagged
    - * addresses to this function.
    - */
    - address = reset_tag(address);
    -
    - shadow_start = kasan_mem_to_shadow(address);
    - shadow_end = kasan_mem_to_shadow(address + size);
    -
    - __memset(shadow_start, value, shadow_end - shadow_start);
    -}
    -
    -void kasan_unpoison_memory(const void *address, size_t size)
    -{
    - u8 tag = get_tag(address);
    -
    - /*
    - * Perform shadow offset calculation based on untagged address, as
    - * some of the callers (e.g. kasan_unpoison_object_data) pass tagged
    - * addresses to this function.
    - */
    - address = reset_tag(address);
    -
    - kasan_poison_memory(address, size, tag);
    -
    - if (size & KASAN_GRANULE_MASK) {
    - u8 *shadow = (u8 *)kasan_mem_to_shadow(address + size);
    -
    - if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
    - *shadow = tag;
    - else
    - *shadow = size & KASAN_GRANULE_MASK;
    - }
    -}
    -
    static void __kasan_unpoison_stack(struct task_struct *task, const void *sp)
    {
    void *base = task_stack_page(task);
    @@ -535,395 +443,3 @@ void kasan_kfree_large(void *ptr, unsigned long ip)
    kasan_report_invalid_free(ptr, ip);
    /* The object will be poisoned by page_alloc. */
    }
    -
    -#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_GRANULE_SIZE) ||
    - WARN_ON(start_kaddr % (KASAN_GRANULE_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_memory:
    - * 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_GRANULE_SIZE);
    - kasan_poison_memory(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_memory(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_GRANULE_SIZE);
    - region_end = ALIGN_DOWN(end, PAGE_SIZE * KASAN_GRANULE_SIZE);
    -
    - free_region_start = ALIGN(free_region_start,
    - PAGE_SIZE * KASAN_GRANULE_SIZE);
    -
    - if (start != region_start &&
    - free_region_start < region_start)
    - region_start -= PAGE_SIZE * KASAN_GRANULE_SIZE;
    -
    - free_region_end = ALIGN_DOWN(free_region_end,
    - PAGE_SIZE * KASAN_GRANULE_SIZE);
    -
    - if (end != region_end &&
    - free_region_end > region_end)
    - region_end += PAGE_SIZE * KASAN_GRANULE_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);
    - }
    -}
    -
    -#else /* 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_GRANULE_SIZE - 1) >>
    - 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
    diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
    new file mode 100644
    index 000000000000..ca0cc4c31454
    --- /dev/null
    +++ b/mm/kasan/shadow.c
    @@ -0,0 +1,505 @@
    +// SPDX-License-Identifier: GPL-2.0
    +/*
    + * This file contains KASAN runtime code that manages shadow memory for
    + * generic and software tag-based KASAN modes.
    + *
    + * Copyright (c) 2014 Samsung Electronics Co., Ltd.
    + * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
    + *
    + * Some code borrowed from https://github.com/xairy/kasan-prototype by
    + * Andrey Konovalov <andreyknvl@gmail.com>
    + */
    +
    +#include <linux/init.h>
    +#include <linux/kasan.h>
    +#include <linux/kernel.h>
    +#include <linux/kmemleak.h>
    +#include <linux/memory.h>
    +#include <linux/mm.h>
    +#include <linux/string.h>
    +#include <linux/types.h>
    +#include <linux/vmalloc.h>
    +
    +#include <asm/cacheflush.h>
    +#include <asm/tlbflush.h>
    +
    +#include "kasan.h"
    +
    +bool __kasan_check_read(const volatile void *p, unsigned int size)
    +{
    + return check_memory_region((unsigned long)p, size, false, _RET_IP_);
    +}
    +EXPORT_SYMBOL(__kasan_check_read);
    +
    +bool __kasan_check_write(const volatile void *p, unsigned int size)
    +{
    + return check_memory_region((unsigned long)p, size, true, _RET_IP_);
    +}
    +EXPORT_SYMBOL(__kasan_check_write);
    +
    +#undef memset
    +void *memset(void *addr, int c, size_t len)
    +{
    + if (!check_memory_region((unsigned long)addr, len, true, _RET_IP_))
    + return NULL;
    +
    + return __memset(addr, c, len);
    +}
    +
    +#ifdef __HAVE_ARCH_MEMMOVE
    +#undef memmove
    +void *memmove(void *dest, const void *src, size_t len)
    +{
    + if (!check_memory_region((unsigned long)src, len, false, _RET_IP_) ||
    + !check_memory_region((unsigned long)dest, len, true, _RET_IP_))
    + return NULL;
    +
    + return __memmove(dest, src, len);
    +}
    +#endif
    +
    +#undef memcpy
    +void *memcpy(void *dest, const void *src, size_t len)
    +{
    + if (!check_memory_region((unsigned long)src, len, false, _RET_IP_) ||
    + !check_memory_region((unsigned long)dest, len, true, _RET_IP_))
    + return NULL;
    +
    + return __memcpy(dest, src, len);
    +}
    +
    +/*
    + * Poisons the shadow memory for 'size' bytes starting from 'addr'.
    + * Memory addresses should be aligned to KASAN_GRANULE_SIZE.
    + */
    +void kasan_poison_memory(const void *address, size_t size, u8 value)
    +{
    + void *shadow_start, *shadow_end;
    +
    + /*
    + * Perform shadow offset calculation based on untagged address, as
    + * some of the callers (e.g. kasan_poison_object_data) pass tagged
    + * addresses to this function.
    + */
    + address = reset_tag(address);
    +
    + shadow_start = kasan_mem_to_shadow(address);
    + shadow_end = kasan_mem_to_shadow(address + size);
    +
    + __memset(shadow_start, value, shadow_end - shadow_start);
    +}
    +
    +void kasan_unpoison_memory(const void *address, size_t size)
    +{
    + u8 tag = get_tag(address);
    +
    + /*
    + * Perform shadow offset calculation based on untagged address, as
    + * some of the callers (e.g. kasan_unpoison_object_data) pass tagged
    + * addresses to this function.
    + */
    + address = reset_tag(address);
    +
    + kasan_poison_memory(address, size, tag);
    +
    + if (size & KASAN_GRANULE_MASK) {
    + u8 *shadow = (u8 *)kasan_mem_to_shadow(address + size);
    +
    + if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
    + *shadow = tag;
    + else
    + *shadow = size & KASAN_GRANULE_MASK;
    + }
    +}
    +
    +#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_GRANULE_SIZE) ||
    + WARN_ON(start_kaddr % (KASAN_GRANULE_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_memory:
    + * 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_GRANULE_SIZE);
    + kasan_poison_memory(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_memory(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_GRANULE_SIZE);
    + region_end = ALIGN_DOWN(end, PAGE_SIZE * KASAN_GRANULE_SIZE);
    +
    + free_region_start = ALIGN(free_region_start,
    + PAGE_SIZE * KASAN_GRANULE_SIZE);
    +
    + if (start != region_start &&
    + free_region_start < region_start)
    + region_start -= PAGE_SIZE * KASAN_GRANULE_SIZE;
    +
    + free_region_end = ALIGN_DOWN(free_region_end,
    + PAGE_SIZE * KASAN_GRANULE_SIZE);
    +
    + if (end != region_end &&
    + free_region_end > region_end)
    + region_end += PAGE_SIZE * KASAN_GRANULE_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);
    + }
    +}
    +
    +#else /* 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_GRANULE_SIZE - 1) >>
    + 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
    --
    2.29.2.222.g5d2a92d10f8-goog
    \
     
     \ /
      Last update: 2020-11-10 23:15    [W:4.688 / U:0.008 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site