kfence, kasan: make KFENCE compatible with KASAN

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.

[akpm@linux-foundation.org: merge fixup]
[andreyknvl@google.com: untag addresses for KFENCE]
Link: https://lkml.kernel.org/r/9dc196006921b191d25d10f6e611316db7da2efc.1611946152.git.andreyknvl@google.com
Link: https://lkml.kernel.org/r/20201103175841.3495947-7-elver@google.com
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Alexander Potapenko <glider@google.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Jann Horn <jannh@google.com>
Co-developed-by: Marco Elver <elver@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christopher Lameter <cl@linux.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hillf Danton <hdanton@sina.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joern Engel <joern@purestorage.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: SeongJae Park <sjpark@amazon.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/lib/Kconfig.kfence b/lib/Kconfig.kfence
index b88ac9d..edfecb5 100644 (file)
--- 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)
        select STACKTRACE
        help
          KFENCE is a low-overhead sampling-based detector of heap out-of-bounds

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index b18189e..af1768c 100644 (file)
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -335,6 +335,9 @@ static bool ____kasan_slab_free(struct kmem_cache *cache, void *object,
        tagged_object = object;
        object = kasan_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);
@@ -413,6 +416,9 @@ static void *____kasan_kmalloc(struct kmem_cache *cache, const void *object,
        if (unlikely(object == NULL))
                return NULL;
 
+       if (is_kfence_address(kasan_reset_tag(object)))
+               return (void *)object;
+
        redzone_start = round_up((unsigned long)(object + size),
                                KASAN_GRANULE_SIZE);
        redzone_end = round_up((unsigned long)object + cache->object_size,

diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
index 3f17a12..2e55e0f 100644 (file)
--- a/mm/kasan/generic.c
+++ b/mm/kasan/generic.c
@@ -14,6 +14,7 @@
 #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>
@@ -331,7 +332,7 @@ void kasan_record_aux_stack(void *addr)
        struct kasan_alloc_meta *alloc_meta;
        void *object;
 
-       if (!(page && PageSlab(page)))
+       if (is_kfence_address(addr) || !(page && PageSlab(page)))
                return;
 
        cache = page->slab_cache;

diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index cc14b6e..fb88374 100644 (file)
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -3,6 +3,7 @@
 #define __MM_KASAN_KASAN_H
 
 #include <linux/kasan.h>
+#include <linux/kfence.h>
 #include <linux/stackdepot.h>
 
 #ifdef CONFIG_KASAN_HW_TAGS
@@ -331,14 +332,28 @@ static inline u8 kasan_random_tag(void) { return 0; }
 
 static inline void kasan_poison(const void *address, size_t size, u8 value)
 {
-       hw_set_mem_tag_range(kasan_reset_tag(address),
+       address = kasan_reset_tag(address);
+
+       /* Skip KFENCE memory if called explicitly outside of sl*b. */
+       if (is_kfence_address(address))
+               return;
+
+       hw_set_mem_tag_range((void *)address,
                        round_up(size, KASAN_GRANULE_SIZE), value);
 }
 
 static inline void kasan_unpoison(const void *address, size_t size)
 {
-       hw_set_mem_tag_range(kasan_reset_tag(address),
-                       round_up(size, KASAN_GRANULE_SIZE), get_tag(address));
+       u8 tag = get_tag(address);
+
+       address = kasan_reset_tag(address);
+
+       /* Skip KFENCE memory if called explicitly outside of sl*b. */
+       if (is_kfence_address(address))
+               return;
+
+       hw_set_mem_tag_range((void *)address,
+                       round_up(size, KASAN_GRANULE_SIZE), tag);
 }
 
 static inline bool kasan_byte_accessible(const void *addr)

diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
index 80adc85..1372a2f 100644 (file)
--- a/mm/kasan/shadow.c
+++ b/mm/kasan/shadow.c
@@ -13,6 +13,7 @@
 #include <linux/init.h>
 #include <linux/kasan.h>
 #include <linux/kernel.h>
+#include <linux/kfence.h>
 #include <linux/kmemleak.h>
 #include <linux/memory.h>
 #include <linux/mm.h>
@@ -84,6 +85,10 @@ void kasan_poison(const void *address, size_t size, u8 value)
        address = kasan_reset_tag(address);
        size = round_up(size, KASAN_GRANULE_SIZE);
 
+       /* 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);
 
@@ -102,6 +107,14 @@ void kasan_unpoison(const void *address, size_t size)
         */
        address = kasan_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(address, size, tag);
 
        if (size & KASAN_GRANULE_MASK) {