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authorAndrey Konovalov <andreyknvl@google.com>2020-12-22 12:02:17 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2020-12-22 12:55:08 -0800
commitaa1ef4d7b3f67f7f17aa4aa34f5ec513c7e4db6c (patch)
treea076c42bb3c60ac54416144165b7bfc7cdc70d42
parent4291e9ee618956eeae02b17f35b272193a6cda5a (diff)
downloadlinux-aa1ef4d7b3f67f7f17aa4aa34f5ec513c7e4db6c.tar.bz2
kasan, mm: reset tags when accessing metadata
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). Link: https://lkml.kernel.org/r/a0f3cefbc49f34c843b664110842de4db28179d0.1606161801.git.andreyknvl@google.com 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> Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Branislav Rankov <Branislav.Rankov@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Evgenii Stepanov <eugenis@google.com> Cc: Kevin Brodsky <kevin.brodsky@arm.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/page_alloc.c4
-rw-r--r--mm/page_poison.c2
-rw-r--r--mm/slub.c29
3 files changed, 20 insertions, 15 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 1887852fb934..7a2c89b21115 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1204,8 +1204,10 @@ 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 06ec518b2089..65cdf844c8ad 100644
--- a/mm/page_poison.c
+++ b/mm/page_poison.c
@@ -25,7 +25,7 @@ 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 4552319148f6..0c8b43a5b3b0 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);
}
@@ -2881,10 +2884,10 @@ redo:
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);