From: Alexander Potapenko <[email protected]>
Make KFENCE compatible with KASAN. Currently this helps test KFENCE
itself, where KASAN can catch potential corruptions to KFENCE state, or
other corruptions that may be a result of freepointer corruptions in the
main allocators.
Reviewed-by: Dmitry Vyukov <[email protected]>
Reviewed-by: Jann Horn <[email protected]>
Co-developed-by: Marco Elver <[email protected]>
Signed-off-by: Marco Elver <[email protected]>
Signed-off-by: Alexander Potapenko <[email protected]>
---
v7:
* Remove EXPERT restriction for enabling KASAN+KFENCE. In future, MTE-based KASAN
without stack traces will benefit from having KFENCE (which has stack
traces). Removing EXPERT restriction allows this for production
builds. The Kconfig help-text should still make it clear that in most
cases KFENCE+KASAN does not make sense.
* Also skip kasan_poison_shadow() if KFENCE object. It turns out that
kernel/scs.c is a user of kasan_{poison,unpoison}_object_data().
* Add Jann's Reviewed-by.
v5:
* Also guard kasan_unpoison_shadow with is_kfence_address(), as it may
be called from SL*B internals, currently ksize().
* Make kasan_record_aux_stack() compatible with KFENCE, which may be
called from outside KASAN runtime.
---
lib/Kconfig.kfence | 2 +-
mm/kasan/common.c | 19 +++++++++++++++++++
mm/kasan/generic.c | 3 ++-
3 files changed, 22 insertions(+), 2 deletions(-)
diff --git a/lib/Kconfig.kfence b/lib/Kconfig.kfence
index b209cd02042b..d2e3c6724226 100644
--- a/lib/Kconfig.kfence
+++ b/lib/Kconfig.kfence
@@ -5,7 +5,7 @@ config HAVE_ARCH_KFENCE
menuconfig KFENCE
bool "KFENCE: low-overhead sampling-based memory safety error detector"
- depends on HAVE_ARCH_KFENCE && !KASAN && (SLAB || SLUB)
+ depends on HAVE_ARCH_KFENCE && (SLAB || SLUB)
depends on JUMP_LABEL # To ensure performance, require jump labels
select STACKTRACE
help
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 950fd372a07e..de92da1b637a 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -18,6 +18,7 @@
#include <linux/init.h>
#include <linux/kasan.h>
#include <linux/kernel.h>
+#include <linux/kfence.h>
#include <linux/kmemleak.h>
#include <linux/linkage.h>
#include <linux/memblock.h>
@@ -124,6 +125,10 @@ void kasan_poison_shadow(const void *address, size_t size, u8 value)
*/
address = reset_tag(address);
+ /* Skip KFENCE memory if called explicitly outside of sl*b. */
+ if (is_kfence_address(address))
+ return;
+
shadow_start = kasan_mem_to_shadow(address);
shadow_end = kasan_mem_to_shadow(address + size);
@@ -141,6 +146,14 @@ void kasan_unpoison_shadow(const void *address, size_t size)
*/
address = reset_tag(address);
+ /*
+ * 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))
+ return;
+
kasan_poison_shadow(address, size, tag);
if (size & KASAN_SHADOW_MASK) {
@@ -396,6 +409,9 @@ static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
tagged_object = object;
object = reset_tag(object);
+ if (is_kfence_address(object))
+ return false;
+
if (unlikely(nearest_obj(cache, virt_to_head_page(object), object) !=
object)) {
kasan_report_invalid_free(tagged_object, ip);
@@ -444,6 +460,9 @@ static void *__kasan_kmalloc(struct kmem_cache *cache, const void *object,
if (unlikely(object == NULL))
return NULL;
+ if (is_kfence_address(object))
+ return (void *)object;
+
redzone_start = round_up((unsigned long)(object + size),
KASAN_SHADOW_SCALE_SIZE);
redzone_end = round_up((unsigned long)object + cache->object_size,
diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
index 248264b9cb76..1069ecd1cd55 100644
--- a/mm/kasan/generic.c
+++ b/mm/kasan/generic.c
@@ -21,6 +21,7 @@
#include <linux/init.h>
#include <linux/kasan.h>
#include <linux/kernel.h>
+#include <linux/kfence.h>
#include <linux/kmemleak.h>
#include <linux/linkage.h>
#include <linux/memblock.h>
@@ -332,7 +333,7 @@ void kasan_record_aux_stack(void *addr)
struct kasan_alloc_meta *alloc_info;
void *object;
- if (!(page && PageSlab(page)))
+ if (is_kfence_address(addr) || !(page && PageSlab(page)))
return;
cache = page->slab_cache;
--
2.29.1.341.ge80a0c044ae-goog