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authorAndrey Konovalov <andreyknvl@google.com>2020-12-10 15:42:14 +1100
committerStephen Rothwell <sfr@canb.auug.org.au>2020-12-16 18:03:01 +1100
commit6c145dcb09b8ca98c31cd79b839473839f684b61 (patch)
treea56729b23ae5df34dd2c16e6c3bebffd403c5f9a
parentecb2c24d2791ff1ba7be63315fda5650069780df (diff)
downloadlinux-6c145dcb09b8ca98c31cd79b839473839f684b61.tar.gz
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: Stephen Rothwell <sfr@canb.auug.org.au>
-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 011d4466f33e..774542e1483e 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 4f893f7b709c..7abc5971ccac 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -250,7 +250,7 @@ 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
@@ -276,6 +276,7 @@ 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);
}
@@ -305,6 +306,7 @@ 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);
}
@@ -539,8 +541,8 @@ 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();
}
@@ -571,7 +573,7 @@ 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,
@@ -584,7 +586,8 @@ 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)
@@ -748,7 +751,7 @@ 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);
@@ -778,7 +781,7 @@ 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;
@@ -874,7 +877,7 @@ 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;
@@ -1119,7 +1122,7 @@ 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();
}
@@ -1572,10 +1575,10 @@ 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);
}
@@ -2891,10 +2894,10 @@ 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);
out:
slab_post_alloc_hook(s, objcg, gfpflags, 1, &object);