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Message-ID: <YBrB6g9e+636CyFh@elver.google.com>
Date: Wed, 3 Feb 2021 16:31:54 +0100
From: Marco Elver <elver@...gle.com>
To: Andrey Konovalov <andreyknvl@...gle.com>
Cc: Catalin Marinas <catalin.marinas@....com>,
Vincenzo Frascino <vincenzo.frascino@....com>,
Dmitry Vyukov <dvyukov@...gle.com>,
Alexander Potapenko <glider@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Will Deacon <will.deacon@....com>,
Andrey Ryabinin <aryabinin@...tuozzo.com>,
Peter Collingbourne <pcc@...gle.com>,
Evgenii Stepanov <eugenis@...gle.com>,
Branislav Rankov <Branislav.Rankov@....com>,
Kevin Brodsky <kevin.brodsky@....com>,
kasan-dev@...glegroups.com, linux-arm-kernel@...ts.infradead.org,
linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 09/12] kasan: ensure poisoning size alignment
On Mon, Feb 01, 2021 at 08:43PM +0100, Andrey Konovalov wrote:
> A previous changes d99f6a10c161 ("kasan: don't round_up too much")
> attempted to simplify the code by adding a round_up(size) call into
> kasan_poison(). While this allows to have less round_up() calls around
> the code, this results in round_up() being called multiple times.
>
> This patch removes round_up() of size from kasan_poison() and ensures
> that all callers round_up() the size explicitly. This patch also adds
> WARN_ON() alignment checks for address and size to kasan_poison() and
> kasan_unpoison().
>
> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
Reviewed-by: Marco Elver <elver@...gle.com>
> ---
> mm/kasan/common.c | 9 ++++++---
> mm/kasan/kasan.h | 33 ++++++++++++++++++++-------------
> mm/kasan/shadow.c | 37 ++++++++++++++++++++++---------------
> 3 files changed, 48 insertions(+), 31 deletions(-)
>
> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> index a51d6ea580b0..5691cca69397 100644
> --- a/mm/kasan/common.c
> +++ b/mm/kasan/common.c
> @@ -261,7 +261,8 @@ void __kasan_unpoison_object_data(struct kmem_cache *cache, void *object)
>
> void __kasan_poison_object_data(struct kmem_cache *cache, void *object)
> {
> - kasan_poison(object, cache->object_size, KASAN_KMALLOC_REDZONE);
> + kasan_poison(object, round_up(cache->object_size, KASAN_GRANULE_SIZE),
> + KASAN_KMALLOC_REDZONE);
> }
>
> /*
> @@ -348,7 +349,8 @@ static bool ____kasan_slab_free(struct kmem_cache *cache, void *object,
> return true;
> }
>
> - kasan_poison(object, cache->object_size, KASAN_KMALLOC_FREE);
> + kasan_poison(object, round_up(cache->object_size, KASAN_GRANULE_SIZE),
> + KASAN_KMALLOC_FREE);
>
> if ((IS_ENABLED(CONFIG_KASAN_GENERIC) && !quarantine))
> return false;
> @@ -490,7 +492,8 @@ static void *____kasan_kmalloc(struct kmem_cache *cache, const void *object,
> /* Poison the aligned part of the redzone. */
> redzone_start = round_up((unsigned long)(object + size),
> KASAN_GRANULE_SIZE);
> - redzone_end = (unsigned long)object + cache->object_size;
> + redzone_end = round_up((unsigned long)(object + cache->object_size),
> + KASAN_GRANULE_SIZE);
> kasan_poison((void *)redzone_start, redzone_end - redzone_start,
> KASAN_KMALLOC_REDZONE);
>
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index 6a2882997f23..2f7400a3412f 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -321,30 +321,37 @@ static inline u8 kasan_random_tag(void) { return 0; }
>
> #ifdef CONFIG_KASAN_HW_TAGS
>
> -static inline void kasan_poison(const void *address, size_t size, u8 value)
> +static inline void kasan_poison(const void *addr, size_t size, u8 value)
> {
> - address = kasan_reset_tag(address);
> + addr = kasan_reset_tag(addr);
>
> /* Skip KFENCE memory if called explicitly outside of sl*b. */
> - if (is_kfence_address(address))
> + if (is_kfence_address(addr))
> return;
>
> - hw_set_mem_tag_range((void *)address,
> - round_up(size, KASAN_GRANULE_SIZE), value);
> + if (WARN_ON((u64)addr & KASAN_GRANULE_MASK))
> + return;
> + if (WARN_ON(size & KASAN_GRANULE_MASK))
> + return;
> +
> + hw_set_mem_tag_range((void *)addr, size, value);
> }
>
> -static inline void kasan_unpoison(const void *address, size_t size)
> +static inline void kasan_unpoison(const void *addr, size_t size)
> {
> - u8 tag = get_tag(address);
> + u8 tag = get_tag(addr);
>
> - address = kasan_reset_tag(address);
> + addr = kasan_reset_tag(addr);
>
> /* Skip KFENCE memory if called explicitly outside of sl*b. */
> - if (is_kfence_address(address))
> + if (is_kfence_address(addr))
> return;
>
> - hw_set_mem_tag_range((void *)address,
> - round_up(size, KASAN_GRANULE_SIZE), tag);
> + if (WARN_ON((u64)addr & KASAN_GRANULE_MASK))
> + return;
> + size = round_up(size, KASAN_GRANULE_SIZE);
> +
> + hw_set_mem_tag_range((void *)addr, size, tag);
> }
>
> static inline bool kasan_byte_accessible(const void *addr)
> @@ -361,7 +368,7 @@ static inline bool kasan_byte_accessible(const void *addr)
> /**
> * kasan_poison - mark the memory range as unaccessible
> * @addr - range start address, must be aligned to KASAN_GRANULE_SIZE
> - * @size - range size
> + * @size - range size, must be aligned to KASAN_GRANULE_SIZE
> * @value - value that's written to metadata for the range
> *
> * The size gets aligned to KASAN_GRANULE_SIZE before marking the range.
> @@ -371,7 +378,7 @@ void kasan_poison(const void *addr, size_t size, u8 value);
> /**
> * kasan_unpoison - mark the memory range as accessible
> * @addr - range start address, must be aligned to KASAN_GRANULE_SIZE
> - * @size - range size
> + * @size - range size, can be unaligned
> *
> * For the tag-based modes, the @size gets aligned to KASAN_GRANULE_SIZE before
> * marking the range.
> diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
> index 1ed7817e4ee6..c97f51c557ea 100644
> --- a/mm/kasan/shadow.c
> +++ b/mm/kasan/shadow.c
> @@ -69,7 +69,7 @@ void *memcpy(void *dest, const void *src, size_t len)
> return __memcpy(dest, src, len);
> }
>
> -void kasan_poison(const void *address, size_t size, u8 value)
> +void kasan_poison(const void *addr, size_t size, u8 value)
> {
> void *shadow_start, *shadow_end;
>
> @@ -78,55 +78,62 @@ void kasan_poison(const void *address, size_t size, u8 value)
> * some of the callers (e.g. kasan_poison_object_data) pass tagged
> * addresses to this function.
> */
> - address = kasan_reset_tag(address);
> + addr = kasan_reset_tag(addr);
>
> /* Skip KFENCE memory if called explicitly outside of sl*b. */
> - if (is_kfence_address(address))
> + if (is_kfence_address(addr))
> return;
>
> - size = round_up(size, KASAN_GRANULE_SIZE);
> - shadow_start = kasan_mem_to_shadow(address);
> - shadow_end = kasan_mem_to_shadow(address + size);
> + if (WARN_ON((u64)addr & KASAN_GRANULE_MASK))
> + return;
> + if (WARN_ON(size & KASAN_GRANULE_MASK))
> + return;
> +
> + shadow_start = kasan_mem_to_shadow(addr);
> + shadow_end = kasan_mem_to_shadow(addr + size);
>
> __memset(shadow_start, value, shadow_end - shadow_start);
> }
> EXPORT_SYMBOL(kasan_poison);
>
> #ifdef CONFIG_KASAN_GENERIC
> -void kasan_poison_last_granule(const void *address, size_t size)
> +void kasan_poison_last_granule(const void *addr, size_t size)
> {
> if (size & KASAN_GRANULE_MASK) {
> - u8 *shadow = (u8 *)kasan_mem_to_shadow(address + size);
> + u8 *shadow = (u8 *)kasan_mem_to_shadow(addr + size);
> *shadow = size & KASAN_GRANULE_MASK;
> }
> }
> #endif
>
> -void kasan_unpoison(const void *address, size_t size)
> +void kasan_unpoison(const void *addr, size_t size)
> {
> - u8 tag = get_tag(address);
> + u8 tag = get_tag(addr);
>
> /*
> * 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 = kasan_reset_tag(address);
> + addr = kasan_reset_tag(addr);
>
> /*
> * Skip KFENCE memory if called explicitly outside of sl*b. Also note
> * that calls to ksize(), where size is not a multiple of machine-word
> * size, would otherwise poison the invalid portion of the word.
> */
> - if (is_kfence_address(address))
> + if (is_kfence_address(addr))
> + return;
> +
> + if (WARN_ON((u64)addr & KASAN_GRANULE_MASK))
> return;
>
> - /* Unpoison round_up(size, KASAN_GRANULE_SIZE) bytes. */
> - kasan_poison(address, size, tag);
> + /* Unpoison all granules that cover the object. */
> + kasan_poison(addr, round_up(size, KASAN_GRANULE_SIZE), tag);
>
> /* Partially poison the last granule for the generic mode. */
> if (IS_ENABLED(CONFIG_KASAN_GENERIC))
> - kasan_poison_last_granule(address, size);
> + kasan_poison_last_granule(addr, size);
> }
>
> #ifdef CONFIG_MEMORY_HOTPLUG
> --
> 2.30.0.365.g02bc693789-goog
>
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