From: Alexander Potapenko <glider@google.com>
To: Andrey Konovalov <andreyknvl@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
Dmitry Vyukov <dvyukov@google.com>,
Andrey Ryabinin <aryabinin@virtuozzo.com>,
Marco Elver <elver@google.com>,
Evgenii Stepanov <eugenis@google.com>,
Branislav Rankov <Branislav.Rankov@arm.com>,
Kevin Brodsky <kevin.brodsky@arm.com>,
Andrew Morton <akpm@linux-foundation.org>,
kasan-dev <kasan-dev@googlegroups.com>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Linux Memory Management List <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v9 41/44] kasan, mm: reset tags when accessing metadata
Date: Thu, 12 Nov 2020 17:10:00 +0100 [thread overview]
Message-ID: <CAG_fn=VixcPo9fTcn0QSRLkFRsC+gcy-w=96BPEjMUc=e5fc_w@mail.gmail.com> (raw)
In-Reply-To: <d0060171a76ace31b26fef1f2713da209099fb99.1605046192.git.andreyknvl@google.com>
On Tue, Nov 10, 2020 at 11:12 PM Andrey Konovalov <andreyknvl@google.com> wrote:
>
> Kernel allocator code accesses metadata for slab objects, that may lie
> out-of-bounds of the object itself, or be accessed when an object is freed.
> Such accesses trigger tag faults and lead to false-positive reports with
> hardware tag-based KASAN.
>
> Software KASAN modes disable instrumentation for allocator code via
> KASAN_SANITIZE Makefile macro, and rely on kasan_enable/disable_current()
> annotations which are used to ignore KASAN reports.
>
> With hardware tag-based KASAN neither of those options are available, as
> it doesn't use compiler instrumetation, no tag faults are ignored, and MTE
> is disabled after the first one.
>
> Instead, reset tags when accessing metadata (currently only for SLUB).
>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> Acked-by: Marco Elver <elver@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
> ---
> Change-Id: I39f3c4d4f29299d4fbbda039bedf230db1c746fb
> ---
> mm/page_alloc.c | 4 +++-
> mm/page_poison.c | 2 +-
> mm/slub.c | 29 ++++++++++++++++-------------
> 3 files changed, 20 insertions(+), 15 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 24b45261e2bd..f1648aee8d88 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1195,8 +1195,10 @@ static void kernel_init_free_pages(struct page *page, int numpages)
>
> /* s390's use of memset() could override KASAN redzones. */
> kasan_disable_current();
> - for (i = 0; i < numpages; i++)
> + for (i = 0; i < numpages; i++) {
> + page_kasan_tag_reset(page + i);
> clear_highpage(page + i);
> + }
> kasan_enable_current();
> }
>
> diff --git a/mm/page_poison.c b/mm/page_poison.c
> index ae0482cded87..e6c994af7518 100644
> --- a/mm/page_poison.c
> +++ b/mm/page_poison.c
> @@ -53,7 +53,7 @@ static void poison_page(struct page *page)
>
> /* KASAN still think the page is in-use, so skip it. */
> kasan_disable_current();
> - memset(addr, PAGE_POISON, PAGE_SIZE);
> + memset(kasan_reset_tag(addr), PAGE_POISON, PAGE_SIZE);
> kasan_enable_current();
> kunmap_atomic(addr);
> }
> diff --git a/mm/slub.c b/mm/slub.c
> index b30be2385d1c..df2fd5b57df1 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -249,7 +249,7 @@ static inline void *freelist_ptr(const struct kmem_cache *s, void *ptr,
> {
> #ifdef CONFIG_SLAB_FREELIST_HARDENED
> /*
> - * When CONFIG_KASAN_SW_TAGS is enabled, ptr_addr might be tagged.
> + * When CONFIG_KASAN_SW/HW_TAGS is enabled, ptr_addr might be tagged.
> * Normally, this doesn't cause any issues, as both set_freepointer()
> * and get_freepointer() are called with a pointer with the same tag.
> * However, there are some issues with CONFIG_SLUB_DEBUG code. For
> @@ -275,6 +275,7 @@ static inline void *freelist_dereference(const struct kmem_cache *s,
>
> static inline void *get_freepointer(struct kmem_cache *s, void *object)
> {
> + object = kasan_reset_tag(object);
> return freelist_dereference(s, object + s->offset);
> }
>
> @@ -304,6 +305,7 @@ static inline void set_freepointer(struct kmem_cache *s, void *object, void *fp)
> BUG_ON(object == fp); /* naive detection of double free or corruption */
> #endif
>
> + freeptr_addr = (unsigned long)kasan_reset_tag((void *)freeptr_addr);
> *(void **)freeptr_addr = freelist_ptr(s, fp, freeptr_addr);
> }
>
> @@ -538,8 +540,8 @@ static void print_section(char *level, char *text, u8 *addr,
> unsigned int length)
> {
> metadata_access_enable();
> - print_hex_dump(level, text, DUMP_PREFIX_ADDRESS, 16, 1, addr,
> - length, 1);
> + print_hex_dump(level, kasan_reset_tag(text), DUMP_PREFIX_ADDRESS,
> + 16, 1, addr, length, 1);
> metadata_access_disable();
> }
>
> @@ -570,7 +572,7 @@ static struct track *get_track(struct kmem_cache *s, void *object,
>
> p = object + get_info_end(s);
>
> - return p + alloc;
> + return kasan_reset_tag(p + alloc);
> }
>
> static void set_track(struct kmem_cache *s, void *object,
> @@ -583,7 +585,8 @@ static void set_track(struct kmem_cache *s, void *object,
> unsigned int nr_entries;
>
> metadata_access_enable();
> - nr_entries = stack_trace_save(p->addrs, TRACK_ADDRS_COUNT, 3);
> + nr_entries = stack_trace_save(kasan_reset_tag(p->addrs),
> + TRACK_ADDRS_COUNT, 3);
> metadata_access_disable();
>
> if (nr_entries < TRACK_ADDRS_COUNT)
> @@ -747,7 +750,7 @@ static __printf(3, 4) void slab_err(struct kmem_cache *s, struct page *page,
>
> static void init_object(struct kmem_cache *s, void *object, u8 val)
> {
> - u8 *p = object;
> + u8 *p = kasan_reset_tag(object);
>
> if (s->flags & SLAB_RED_ZONE)
> memset(p - s->red_left_pad, val, s->red_left_pad);
> @@ -777,7 +780,7 @@ static int check_bytes_and_report(struct kmem_cache *s, struct page *page,
> u8 *addr = page_address(page);
>
> metadata_access_enable();
> - fault = memchr_inv(start, value, bytes);
> + fault = memchr_inv(kasan_reset_tag(start), value, bytes);
> metadata_access_disable();
> if (!fault)
> return 1;
> @@ -873,7 +876,7 @@ static int slab_pad_check(struct kmem_cache *s, struct page *page)
>
> pad = end - remainder;
> metadata_access_enable();
> - fault = memchr_inv(pad, POISON_INUSE, remainder);
> + fault = memchr_inv(kasan_reset_tag(pad), POISON_INUSE, remainder);
> metadata_access_disable();
> if (!fault)
> return 1;
> @@ -1118,7 +1121,7 @@ void setup_page_debug(struct kmem_cache *s, struct page *page, void *addr)
> return;
>
> metadata_access_enable();
> - memset(addr, POISON_INUSE, page_size(page));
> + memset(kasan_reset_tag(addr), POISON_INUSE, page_size(page));
> metadata_access_disable();
> }
>
> @@ -1566,10 +1569,10 @@ static inline bool slab_free_freelist_hook(struct kmem_cache *s,
> * Clear the object and the metadata, but don't touch
> * the redzone.
> */
> - memset(object, 0, s->object_size);
> + memset(kasan_reset_tag(object), 0, s->object_size);
> rsize = (s->flags & SLAB_RED_ZONE) ? s->red_left_pad
> : 0;
> - memset((char *)object + s->inuse, 0,
> + memset((char *)kasan_reset_tag(object) + s->inuse, 0,
> s->size - s->inuse - rsize);
>
> }
> @@ -2883,10 +2886,10 @@ static __always_inline void *slab_alloc_node(struct kmem_cache *s,
> stat(s, ALLOC_FASTPATH);
> }
>
> - maybe_wipe_obj_freeptr(s, object);
> + maybe_wipe_obj_freeptr(s, kasan_reset_tag(object));
>
> if (unlikely(slab_want_init_on_alloc(gfpflags, s)) && object)
> - memset(object, 0, s->object_size);
> + memset(kasan_reset_tag(object), 0, s->object_size);
>
> slab_post_alloc_hook(s, objcg, gfpflags, 1, &object);
>
> --
> 2.29.2.222.g5d2a92d10f8-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
next prev parent reply other threads:[~2020-11-12 16:10 UTC|newest]
Thread overview: 107+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-10 22:09 [PATCH v9 00/44] kasan: add hardware tag-based mode for arm64 Andrey Konovalov
2020-11-10 22:09 ` [PATCH v9 01/44] kasan: drop unnecessary GPL text from comment headers Andrey Konovalov
2020-11-11 13:16 ` Alexander Potapenko
2020-11-10 22:09 ` [PATCH v9 02/44] kasan: KASAN_VMALLOC depends on KASAN_GENERIC Andrey Konovalov
2020-11-11 13:19 ` Alexander Potapenko
2020-11-10 22:10 ` [PATCH v9 03/44] kasan: group vmalloc code Andrey Konovalov
2020-11-11 13:21 ` Alexander Potapenko
2020-11-10 22:10 ` [PATCH v9 04/44] s390/kasan: include asm/page.h from asm/kasan.h Andrey Konovalov
2020-11-10 22:10 ` [PATCH v9 05/44] kasan: shadow declarations only for software modes Andrey Konovalov
2020-11-11 13:25 ` Alexander Potapenko
2020-11-10 22:10 ` [PATCH v9 06/44] kasan: rename (un)poison_shadow to (un)poison_memory Andrey Konovalov
2020-11-11 13:26 ` Alexander Potapenko
2020-11-10 22:10 ` [PATCH v9 07/44] kasan: rename KASAN_SHADOW_* to KASAN_GRANULE_* Andrey Konovalov
2020-11-11 13:45 ` Alexander Potapenko
2020-11-10 22:10 ` [PATCH v9 08/44] kasan: only build init.c for software modes Andrey Konovalov
2020-11-11 13:46 ` Alexander Potapenko
2020-11-10 22:10 ` [PATCH v9 09/44] kasan: split out shadow.c from common.c Andrey Konovalov
2020-11-11 14:07 ` Alexander Potapenko
2020-11-10 22:10 ` [PATCH v9 10/44] kasan: define KASAN_GRANULE_PAGE Andrey Konovalov
2020-11-11 14:13 ` Alexander Potapenko
2020-11-11 18:47 ` Andrey Konovalov
2020-11-11 19:04 ` Marco Elver
2020-11-12 0:05 ` Andrey Konovalov
2020-11-10 22:10 ` [PATCH v9 11/44] kasan: rename report and tags files Andrey Konovalov
2020-11-11 14:15 ` Alexander Potapenko
2020-11-10 22:10 ` [PATCH v9 12/44] kasan: don't duplicate config dependencies Andrey Konovalov
2020-11-11 14:20 ` Alexander Potapenko
2020-11-10 22:10 ` [PATCH v9 13/44] kasan: hide invalid free check implementation Andrey Konovalov
2020-11-11 14:23 ` Alexander Potapenko
2020-11-10 22:10 ` [PATCH v9 14/44] kasan: decode stack frame only with KASAN_STACK_ENABLE Andrey Konovalov
2020-11-11 14:25 ` Alexander Potapenko
2020-11-10 22:10 ` [PATCH v9 15/44] kasan, arm64: only init shadow for software modes Andrey Konovalov
2020-11-11 14:30 ` Alexander Potapenko
2020-11-10 22:10 ` [PATCH v9 16/44] kasan, arm64: only use kasan_depth " Andrey Konovalov
2020-11-11 14:59 ` Alexander Potapenko
2020-11-10 22:10 ` [PATCH v9 17/44] kasan, arm64: move initialization message Andrey Konovalov
2020-11-11 15:03 ` Alexander Potapenko
2020-11-11 18:50 ` Andrey Konovalov
2020-11-12 15:09 ` Alexander Potapenko
2020-11-10 22:10 ` [PATCH v9 18/44] kasan, arm64: rename kasan_init_tags and mark as __init Andrey Konovalov
2020-11-11 15:05 ` Alexander Potapenko
2020-11-10 22:10 ` [PATCH v9 19/44] kasan: rename addr_has_shadow to addr_has_metadata Andrey Konovalov
2020-11-11 15:06 ` Alexander Potapenko
2020-11-10 22:10 ` [PATCH v9 20/44] kasan: rename print_shadow_for_address to print_memory_metadata Andrey Konovalov
2020-11-11 15:07 ` Alexander Potapenko
2020-11-10 22:10 ` [PATCH v9 21/44] kasan: kasan_non_canonical_hook only for software modes Andrey Konovalov
2020-11-11 15:08 ` Alexander Potapenko
2020-11-11 18:52 ` Andrey Konovalov
2020-11-12 15:16 ` Alexander Potapenko
2020-11-12 19:27 ` Andrey Konovalov
2020-11-10 22:10 ` [PATCH v9 22/44] kasan: rename SHADOW layout macros to META Andrey Konovalov
2020-11-11 15:18 ` Alexander Potapenko
2020-11-10 22:10 ` [PATCH v9 23/44] kasan: separate metadata_fetch_row for each mode Andrey Konovalov
2020-11-11 15:22 ` Alexander Potapenko
2020-11-11 16:19 ` Alexander Potapenko
2020-11-10 22:10 ` [PATCH v9 24/44] kasan, arm64: don't allow SW_TAGS with ARM64_MTE Andrey Konovalov
2020-11-11 15:52 ` Alexander Potapenko
2020-11-10 22:10 ` [PATCH v9 25/44] kasan: introduce CONFIG_KASAN_HW_TAGS Andrey Konovalov
2020-11-11 15:58 ` Alexander Potapenko
2020-11-11 18:53 ` Andrey Konovalov
2020-11-10 22:10 ` [PATCH v9 26/44] arm64: Enable armv8.5-a asm-arch option Andrey Konovalov
2020-11-10 22:10 ` [PATCH v9 27/44] arm64: mte: Add in-kernel MTE helpers Andrey Konovalov
2020-11-10 22:10 ` [PATCH v9 28/44] arm64: mte: Reset the page tag in page->flags Andrey Konovalov
2020-11-12 9:31 ` Catalin Marinas
2020-11-12 9:39 ` Vincenzo Frascino
2020-11-10 22:10 ` [PATCH v9 29/44] arm64: mte: Add in-kernel tag fault handler Andrey Konovalov
2020-11-10 22:10 ` [PATCH v9 30/44] arm64: kasan: Allow enabling in-kernel MTE Andrey Konovalov
2020-11-12 9:43 ` Catalin Marinas
2020-11-12 16:46 ` Vincenzo Frascino
2020-11-13 11:17 ` Vincenzo Frascino
2020-11-13 12:00 ` Catalin Marinas
2020-11-13 12:04 ` Vincenzo Frascino
2020-11-10 22:10 ` [PATCH v9 31/44] arm64: mte: Convert gcr_user into an exclude mask Andrey Konovalov
2020-11-10 22:10 ` [PATCH v9 32/44] arm64: mte: Switch GCR_EL1 in kernel entry and exit Andrey Konovalov
2020-11-12 9:39 ` Catalin Marinas
2020-11-12 9:45 ` Vincenzo Frascino
2020-11-12 9:45 ` Catalin Marinas
2020-11-12 9:55 ` Vincenzo Frascino
2020-11-10 22:10 ` [PATCH v9 33/44] kasan, mm: untag page address in free_reserved_area Andrey Konovalov
2020-11-10 22:10 ` [PATCH v9 34/44] arm64: kasan: Align allocations for HW_TAGS Andrey Konovalov
2020-11-11 16:10 ` Alexander Potapenko
2020-11-10 22:10 ` [PATCH v9 35/44] arm64: kasan: Add arch layer for memory tagging helpers Andrey Konovalov
2020-11-10 22:10 ` [PATCH v9 36/44] kasan: define KASAN_GRANULE_SIZE for HW_TAGS Andrey Konovalov
2020-11-11 16:13 ` Alexander Potapenko
2020-11-10 22:10 ` [PATCH v9 37/44] kasan, x86, s390: update undef CONFIG_KASAN Andrey Konovalov
2020-11-11 16:15 ` Alexander Potapenko
2020-11-10 22:10 ` [PATCH v9 38/44] kasan, arm64: expand CONFIG_KASAN checks Andrey Konovalov
2020-11-11 16:22 ` Alexander Potapenko
2020-11-10 22:10 ` [PATCH v9 39/44] kasan, arm64: implement HW_TAGS runtime Andrey Konovalov
2020-11-12 17:37 ` Alexander Potapenko
2020-11-10 22:10 ` [PATCH v9 40/44] kasan, arm64: print report from tag fault handler Andrey Konovalov
2020-11-11 16:43 ` Alexander Potapenko
2020-11-10 22:10 ` [PATCH v9 41/44] kasan, mm: reset tags when accessing metadata Andrey Konovalov
2020-11-12 16:10 ` Alexander Potapenko [this message]
2020-11-10 22:10 ` [PATCH v9 42/44] kasan, arm64: enable CONFIG_KASAN_HW_TAGS Andrey Konovalov
2020-11-11 16:49 ` Alexander Potapenko
2020-11-10 22:10 ` [PATCH v9 43/44] kasan: add documentation for hardware tag-based mode Andrey Konovalov
2020-11-11 16:57 ` Alexander Potapenko
2020-11-11 18:54 ` Andrey Konovalov
2020-11-10 22:10 ` [PATCH v9 44/44] kselftest/arm64: Check GCR_EL1 after context switch Andrey Konovalov
2020-11-12 9:46 ` Catalin Marinas
2020-11-12 15:59 ` Alexander Potapenko
2020-11-12 16:09 ` Marco Elver
2020-11-12 16:41 ` Alexander Potapenko
2020-11-13 11:47 ` Vincenzo Frascino
2020-11-10 22:54 ` [PATCH v9 00/44] kasan: add hardware tag-based mode for arm64 Andrew Morton
2020-11-11 14:35 ` Andrey Konovalov
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