Re: [PATCH v2 05/37] kasan: rename KASAN_SHADOW_* to KASAN_GRANULE_*

From: Alexander Potapenko
Date: Fri Sep 18 2020 - 04:04:20 EST

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On Tue, Sep 15, 2020 at 11:16 PM Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote:
>
> 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, but will still use the concept
> of memory granules.

KASAN documentation doesn't seem to explain this concept anywhere (I
also checked the "kasan: add documentation for hardware tag-based
mode" patch), looks like it's only mentioned in MTE documentation.
Could you please elaborate on what we consider a granule in each of KASAN modes?

> Rename KASAN_SHADOW_SCALE_SIZE to KASAN_GRANULE_SIZE,
> and KASAN_SHADOW_MASK to KASAN_GRANULE_MASK.
>
> Also use MASK when used as a mask, otherwise use SIZE.
>
> No functional changes.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
> ---
> Change-Id: Iac733e2248aa9d29f6fc425d8946ba07cca73ecf
> ---
> Documentation/dev-tools/kasan.rst | 2 +-
> lib/test_kasan.c | 2 +-
> mm/kasan/common.c | 39 ++++++++++++++++---------------
> mm/kasan/generic.c | 14 +++++------
> mm/kasan/generic_report.c | 8 +++----
> mm/kasan/init.c | 8 +++----
> mm/kasan/kasan.h | 4 ++--
> mm/kasan/report.c | 10 ++++----
> mm/kasan/tags_report.c | 2 +-
> 9 files changed, 45 insertions(+), 44 deletions(-)
>
> diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
> index 38fd5681fade..a3030fc6afe5 100644
> --- a/Documentation/dev-tools/kasan.rst
> +++ b/Documentation/dev-tools/kasan.rst
> @@ -264,7 +264,7 @@ Most mappings in vmalloc space are small, requiring less than a full
> page of shadow space. Allocating a full shadow page per mapping would
> therefore be wasteful. Furthermore, to ensure that different mappings
> use different shadow pages, mappings would have to be aligned to
> -``KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE``.
> +``KASAN_GRANULE_SIZE * PAGE_SIZE``.
>
> Instead, we share backing space across multiple mappings. We allocate
> a backing page when a mapping in vmalloc space uses a particular page
> diff --git a/lib/test_kasan.c b/lib/test_kasan.c
> index 53e953bb1d1d..ddd0b80f24a1 100644
> --- a/lib/test_kasan.c
> +++ b/lib/test_kasan.c
> @@ -25,7 +25,7 @@
>
> #include "../mm/kasan/kasan.h"
>
> -#define OOB_TAG_OFF (IS_ENABLED(CONFIG_KASAN_GENERIC) ? 0 : KASAN_SHADOW_SCALE_SIZE)
> +#define OOB_TAG_OFF (IS_ENABLED(CONFIG_KASAN_GENERIC) ? 0 : KASAN_GRANULE_SIZE)
>
> /*
> * We assign some test results to these globals to make sure the tests
> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> index 65933b27df81..c9daf2c33651 100644
> --- a/mm/kasan/common.c
> +++ b/mm/kasan/common.c
> @@ -111,7 +111,7 @@ void *memcpy(void *dest, const void *src, size_t len)
>
> /*
> * Poisons the shadow memory for 'size' bytes starting from 'addr'.
> - * Memory addresses should be aligned to KASAN_SHADOW_SCALE_SIZE.
> + * Memory addresses should be aligned to KASAN_GRANULE_SIZE.
> */
> void kasan_poison_memory(const void *address, size_t size, u8 value)
> {
> @@ -143,13 +143,13 @@ void kasan_unpoison_memory(const void *address, size_t size)
>
> kasan_poison_memory(address, size, tag);
>
> - if (size & KASAN_SHADOW_MASK) {
> + 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_SHADOW_MASK;
> + *shadow = size & KASAN_GRANULE_MASK;
> }
> }
>
> @@ -301,7 +301,7 @@ void kasan_unpoison_object_data(struct kmem_cache *cache, void *object)
> void kasan_poison_object_data(struct kmem_cache *cache, void *object)
> {
> kasan_poison_memory(object,
> - round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE),
> + round_up(cache->object_size, KASAN_GRANULE_SIZE),
> KASAN_KMALLOC_REDZONE);
> }
>
> @@ -373,7 +373,7 @@ static inline bool shadow_invalid(u8 tag, s8 shadow_byte)
> {
> if (IS_ENABLED(CONFIG_KASAN_GENERIC))
> return shadow_byte < 0 ||
> - shadow_byte >= KASAN_SHADOW_SCALE_SIZE;
> + shadow_byte >= KASAN_GRANULE_SIZE;
>
> /* else CONFIG_KASAN_SW_TAGS: */
> if ((u8)shadow_byte == KASAN_TAG_INVALID)
> @@ -412,7 +412,7 @@ static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
> return true;
> }
>
> - rounded_up_size = round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE);
> + rounded_up_size = round_up(cache->object_size, KASAN_GRANULE_SIZE);
> kasan_poison_memory(object, rounded_up_size, KASAN_KMALLOC_FREE);
>
> if ((IS_ENABLED(CONFIG_KASAN_GENERIC) && !quarantine) ||
> @@ -445,9 +445,9 @@ static void *__kasan_kmalloc(struct kmem_cache *cache, const void *object,
> return NULL;
>
> redzone_start = round_up((unsigned long)(object + size),
> - KASAN_SHADOW_SCALE_SIZE);
> + KASAN_GRANULE_SIZE);
> redzone_end = round_up((unsigned long)object + cache->object_size,
> - KASAN_SHADOW_SCALE_SIZE);
> + KASAN_GRANULE_SIZE);
>
> if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
> tag = assign_tag(cache, object, false, keep_tag);
> @@ -491,7 +491,7 @@ void * __must_check kasan_kmalloc_large(const void *ptr, size_t size,
>
> page = virt_to_page(ptr);
> redzone_start = round_up((unsigned long)(ptr + size),
> - KASAN_SHADOW_SCALE_SIZE);
> + KASAN_GRANULE_SIZE);
> redzone_end = (unsigned long)ptr + page_size(page);
>
> kasan_unpoison_memory(ptr, size);
> @@ -589,8 +589,8 @@ static int __meminit kasan_mem_notifier(struct notifier_block *nb,
> 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)))
> + if (WARN_ON(mem_data->nr_pages % KASAN_GRANULE_SIZE) ||
> + WARN_ON(start_kaddr % (KASAN_GRANULE_SIZE << PAGE_SHIFT)))
> return NOTIFY_BAD;
>
> switch (action) {
> @@ -748,7 +748,7 @@ 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);
> + size = round_up(size, KASAN_GRANULE_SIZE);
> kasan_poison_memory(start, size, KASAN_VMALLOC_INVALID);
> }
>
> @@ -861,22 +861,22 @@ void kasan_release_vmalloc(unsigned long start, unsigned long 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);
> + 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_SHADOW_SCALE_SIZE);
> + PAGE_SIZE * KASAN_GRANULE_SIZE);
>
> if (start != region_start &&
> free_region_start < region_start)
> - region_start -= PAGE_SIZE * KASAN_SHADOW_SCALE_SIZE;
> + region_start -= PAGE_SIZE * KASAN_GRANULE_SIZE;
>
> free_region_end = ALIGN_DOWN(free_region_end,
> - PAGE_SIZE * KASAN_SHADOW_SCALE_SIZE);
> + PAGE_SIZE * KASAN_GRANULE_SIZE);
>
> if (end != region_end &&
> free_region_end > region_end)
> - region_end += PAGE_SIZE * KASAN_SHADOW_SCALE_SIZE;
> + 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);
> @@ -902,7 +902,8 @@ int kasan_module_alloc(void *addr, size_t size)
> unsigned long shadow_start;
>
> shadow_start = (unsigned long)kasan_mem_to_shadow(addr);
> - scaled_size = (size + KASAN_SHADOW_MASK) >> KASAN_SHADOW_SCALE_SHIFT;
> + 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)))
> diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
> index 4b5f905198d8..f6d68aa9872f 100644
> --- a/mm/kasan/generic.c
> +++ b/mm/kasan/generic.c
> @@ -51,7 +51,7 @@ static __always_inline bool memory_is_poisoned_1(unsigned long addr)
> s8 shadow_value = *(s8 *)kasan_mem_to_shadow((void *)addr);
>
> if (unlikely(shadow_value)) {
> - s8 last_accessible_byte = addr & KASAN_SHADOW_MASK;
> + s8 last_accessible_byte = addr & KASAN_GRANULE_MASK;
> return unlikely(last_accessible_byte >= shadow_value);
> }
>
> @@ -67,7 +67,7 @@ static __always_inline bool memory_is_poisoned_2_4_8(unsigned long addr,
> * Access crosses 8(shadow size)-byte boundary. Such access maps
> * into 2 shadow bytes, so we need to check them both.
> */
> - if (unlikely(((addr + size - 1) & KASAN_SHADOW_MASK) < size - 1))
> + if (unlikely(((addr + size - 1) & KASAN_GRANULE_MASK) < size - 1))
> return *shadow_addr || memory_is_poisoned_1(addr + size - 1);
>
> return memory_is_poisoned_1(addr + size - 1);
> @@ -78,7 +78,7 @@ static __always_inline bool memory_is_poisoned_16(unsigned long addr)
> u16 *shadow_addr = (u16 *)kasan_mem_to_shadow((void *)addr);
>
> /* Unaligned 16-bytes access maps into 3 shadow bytes. */
> - if (unlikely(!IS_ALIGNED(addr, KASAN_SHADOW_SCALE_SIZE)))
> + if (unlikely(!IS_ALIGNED(addr, KASAN_GRANULE_SIZE)))
> return *shadow_addr || memory_is_poisoned_1(addr + 15);
>
> return *shadow_addr;
> @@ -139,7 +139,7 @@ static __always_inline bool memory_is_poisoned_n(unsigned long addr,
> s8 *last_shadow = (s8 *)kasan_mem_to_shadow((void *)last_byte);
>
> if (unlikely(ret != (unsigned long)last_shadow ||
> - ((long)(last_byte & KASAN_SHADOW_MASK) >= *last_shadow)))
> + ((long)(last_byte & KASAN_GRANULE_MASK) >= *last_shadow)))
> return true;
> }
> return false;
> @@ -205,7 +205,7 @@ void kasan_cache_shutdown(struct kmem_cache *cache)
>
> static void register_global(struct kasan_global *global)
> {
> - size_t aligned_size = round_up(global->size, KASAN_SHADOW_SCALE_SIZE);
> + size_t aligned_size = round_up(global->size, KASAN_GRANULE_SIZE);
>
> kasan_unpoison_memory(global->beg, global->size);
>
> @@ -279,10 +279,10 @@ EXPORT_SYMBOL(__asan_handle_no_return);
> /* Emitted by compiler to poison alloca()ed objects. */
> void __asan_alloca_poison(unsigned long addr, size_t size)
> {
> - size_t rounded_up_size = round_up(size, KASAN_SHADOW_SCALE_SIZE);
> + size_t rounded_up_size = round_up(size, KASAN_GRANULE_SIZE);
> size_t padding_size = round_up(size, KASAN_ALLOCA_REDZONE_SIZE) -
> rounded_up_size;
> - size_t rounded_down_size = round_down(size, KASAN_SHADOW_SCALE_SIZE);
> + size_t rounded_down_size = round_down(size, KASAN_GRANULE_SIZE);
>
> const void *left_redzone = (const void *)(addr -
> KASAN_ALLOCA_REDZONE_SIZE);
> diff --git a/mm/kasan/generic_report.c b/mm/kasan/generic_report.c
> index a38c7a9e192a..4dce1633b082 100644
> --- a/mm/kasan/generic_report.c
> +++ b/mm/kasan/generic_report.c
> @@ -39,7 +39,7 @@ void *find_first_bad_addr(void *addr, size_t size)
> void *p = addr;
>
> while (p < addr + size && !(*(u8 *)kasan_mem_to_shadow(p)))
> - p += KASAN_SHADOW_SCALE_SIZE;
> + p += KASAN_GRANULE_SIZE;
> return p;
> }
>
> @@ -51,14 +51,14 @@ static const char *get_shadow_bug_type(struct kasan_access_info *info)
> shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr);
>
> /*
> - * If shadow byte value is in [0, KASAN_SHADOW_SCALE_SIZE) we can look
> + * If shadow byte value is in [0, KASAN_GRANULE_SIZE) we can look
> * at the next shadow byte to determine the type of the bad access.
> */
> - if (*shadow_addr > 0 && *shadow_addr <= KASAN_SHADOW_SCALE_SIZE - 1)
> + if (*shadow_addr > 0 && *shadow_addr <= KASAN_GRANULE_SIZE - 1)
> shadow_addr++;
>
> switch (*shadow_addr) {
> - case 0 ... KASAN_SHADOW_SCALE_SIZE - 1:
> + case 0 ... KASAN_GRANULE_SIZE - 1:
> /*
> * In theory it's still possible to see these shadow values
> * due to a data race in the kernel code.
> diff --git a/mm/kasan/init.c b/mm/kasan/init.c
> index fe6be0be1f76..754b641c83c7 100644
> --- a/mm/kasan/init.c
> +++ b/mm/kasan/init.c
> @@ -447,8 +447,8 @@ void kasan_remove_zero_shadow(void *start, unsigned long size)
> end = addr + (size >> KASAN_SHADOW_SCALE_SHIFT);
>
> if (WARN_ON((unsigned long)start %
> - (KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE)) ||
> - WARN_ON(size % (KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE)))
> + (KASAN_GRANULE_SIZE * PAGE_SIZE)) ||
> + WARN_ON(size % (KASAN_GRANULE_SIZE * PAGE_SIZE)))
> return;
>
> for (; addr < end; addr = next) {
> @@ -482,8 +482,8 @@ int kasan_add_zero_shadow(void *start, unsigned long size)
> shadow_end = shadow_start + (size >> KASAN_SHADOW_SCALE_SHIFT);
>
> if (WARN_ON((unsigned long)start %
> - (KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE)) ||
> - WARN_ON(size % (KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE)))
> + (KASAN_GRANULE_SIZE * PAGE_SIZE)) ||
> + WARN_ON(size % (KASAN_GRANULE_SIZE * PAGE_SIZE)))
> return -EINVAL;
>
> ret = kasan_populate_early_shadow(shadow_start, shadow_end);
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index 03450d3b31f7..c31e2c739301 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -5,8 +5,8 @@
> #include <linux/kasan.h>
> #include <linux/stackdepot.h>
>
> -#define KASAN_SHADOW_SCALE_SIZE (1UL << KASAN_SHADOW_SCALE_SHIFT)
> -#define KASAN_SHADOW_MASK (KASAN_SHADOW_SCALE_SIZE - 1)
> +#define KASAN_GRANULE_SIZE (1UL << KASAN_SHADOW_SCALE_SHIFT)
> +#define KASAN_GRANULE_MASK (KASAN_GRANULE_SIZE - 1)
>
> #define KASAN_TAG_KERNEL 0xFF /* native kernel pointers tag */
> #define KASAN_TAG_INVALID 0xFE /* inaccessible memory tag */
> diff --git a/mm/kasan/report.c b/mm/kasan/report.c
> index 4f49fa6cd1aa..7c025d792e2f 100644
> --- a/mm/kasan/report.c
> +++ b/mm/kasan/report.c
> @@ -317,24 +317,24 @@ static bool __must_check get_address_stack_frame_info(const void *addr,
> return false;
>
> aligned_addr = round_down((unsigned long)addr, sizeof(long));
> - mem_ptr = round_down(aligned_addr, KASAN_SHADOW_SCALE_SIZE);
> + mem_ptr = round_down(aligned_addr, KASAN_GRANULE_SIZE);
> shadow_ptr = kasan_mem_to_shadow((void *)aligned_addr);
> shadow_bottom = kasan_mem_to_shadow(end_of_stack(current));
>
> while (shadow_ptr >= shadow_bottom && *shadow_ptr != KASAN_STACK_LEFT) {
> shadow_ptr--;
> - mem_ptr -= KASAN_SHADOW_SCALE_SIZE;
> + mem_ptr -= KASAN_GRANULE_SIZE;
> }
>
> while (shadow_ptr >= shadow_bottom && *shadow_ptr == KASAN_STACK_LEFT) {
> shadow_ptr--;
> - mem_ptr -= KASAN_SHADOW_SCALE_SIZE;
> + mem_ptr -= KASAN_GRANULE_SIZE;
> }
>
> if (shadow_ptr < shadow_bottom)
> return false;
>
> - frame = (const unsigned long *)(mem_ptr + KASAN_SHADOW_SCALE_SIZE);
> + frame = (const unsigned long *)(mem_ptr + KASAN_GRANULE_SIZE);
> if (frame[0] != KASAN_CURRENT_STACK_FRAME_MAGIC) {
> pr_err("KASAN internal error: frame info validation failed; invalid marker: %lu\n",
> frame[0]);
> @@ -572,6 +572,6 @@ void kasan_non_canonical_hook(unsigned long addr)
> else
> bug_type = "maybe wild-memory-access";
> pr_alert("KASAN: %s in range [0x%016lx-0x%016lx]\n", bug_type,
> - orig_addr, orig_addr + KASAN_SHADOW_MASK);
> + orig_addr, orig_addr + KASAN_GRANULE_SIZE - 1);
> }
> #endif
> diff --git a/mm/kasan/tags_report.c b/mm/kasan/tags_report.c
> index bee43717d6f0..6ddb55676a7c 100644
> --- a/mm/kasan/tags_report.c
> +++ b/mm/kasan/tags_report.c
> @@ -81,7 +81,7 @@ void *find_first_bad_addr(void *addr, size_t size)
> void *end = p + size;
>
> while (p < end && tag == *(u8 *)kasan_mem_to_shadow(p))
> - p += KASAN_SHADOW_SCALE_SIZE;
> + p += KASAN_GRANULE_SIZE;
> return p;
> }
>
> --
> 2.28.0.618.gf4bc123cb7-goog
>

--
Alexander Potapenko
Software Engineer

Google Germany GmbH
Erika-Mann-Straße, 33
80636 München

Geschäftsführer: Paul Manicle, Halimah DeLaine Prado
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg

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