| Message ID | a9229404628ab379bc74010125333f110771d4b6.1600987622.git.andreyknvl@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | kasan: add hardware tag-based mode for arm64 | expand |
On Fri, Sep 25, 2020 at 12:50AM +0200, Andrey Konovalov wrote: > SLUB allocator 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. > > Signed-off-by: Andrey Konovalov <andreyknvl@google.com> > Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com> Acked-by: Marco Elver <elver@google.com> I assume you have tested with the various SLUB debug options, as well as things like memory initialization etc? > --- > Change-Id: I39f3c4d4f29299d4fbbda039bedf230db1c746fb > --- > mm/page_poison.c | 2 +- > mm/slub.c | 25 ++++++++++++++----------- > 2 files changed, 15 insertions(+), 12 deletions(-) > > diff --git a/mm/page_poison.c b/mm/page_poison.c > index 34b9181ee5d1..d90d342a391f 100644 > --- a/mm/page_poison.c > +++ b/mm/page_poison.c > @@ -43,7 +43,7 @@ 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 68c02b2eecd9..f5b4bef3cd6c 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(); > } > > @@ -2884,10 +2887,10 @@ 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); > > -- > 2.28.0.681.g6f77f65b4e-goog >
On Thu, Oct 1, 2020 at 8:03 PM <elver@google.com> wrote: > > On Fri, Sep 25, 2020 at 12:50AM +0200, Andrey Konovalov wrote: > > SLUB allocator 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. > > > > Signed-off-by: Andrey Konovalov <andreyknvl@google.com> > > Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com> > > Acked-by: Marco Elver <elver@google.com> > > I assume you have tested with the various SLUB debug options, Yes. > as well as > things like memory initialization etc? Will test before sending v4. Thanks! > > > --- > > Change-Id: I39f3c4d4f29299d4fbbda039bedf230db1c746fb > > --- > > mm/page_poison.c | 2 +- > > mm/slub.c | 25 ++++++++++++++----------- > > 2 files changed, 15 insertions(+), 12 deletions(-) > > > > diff --git a/mm/page_poison.c b/mm/page_poison.c > > index 34b9181ee5d1..d90d342a391f 100644 > > --- a/mm/page_poison.c > > +++ b/mm/page_poison.c > > @@ -43,7 +43,7 @@ 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 68c02b2eecd9..f5b4bef3cd6c 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(); > > } > > > > @@ -2884,10 +2887,10 @@ 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); > > > > -- > > 2.28.0.681.g6f77f65b4e-goog > >
diff --git a/mm/page_poison.c b/mm/page_poison.c index 34b9181ee5d1..d90d342a391f 100644 --- a/mm/page_poison.c +++ b/mm/page_poison.c @@ -43,7 +43,7 @@ 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 68c02b2eecd9..f5b4bef3cd6c 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(); } @@ -2884,10 +2887,10 @@ 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);