linux-kernel - [PATCH mm] kasan: untag addresses for KFENCE

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Message-Id: <9dc196006921b191d25d10f6e611316db7da2efc.1611946152.git.andreyknvl@google.com>
Date:   Fri, 29 Jan 2021 19:50:22 +0100
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Marco Elver <elver@...gle.com>, kasan-dev@...glegroups.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: [PATCH mm] kasan: untag addresses for KFENCE

KFENCE annotations operate on untagged addresses.

Untag addresses in KASAN runtime where they might be tagged.

Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>

---

This can be squashed into:

revert kasan-remove-kfence-leftovers
kfence, kasan: make KFENCE compatible with KASA

---
 mm/kasan/common.c |  2 +-
 mm/kasan/kasan.h  | 12 +++++++++---
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index a390fae9d64b..fe852f3cfa42 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -416,7 +416,7 @@ static void *____kasan_kmalloc(struct kmem_cache *cache, const void *object,
 	if (unlikely(object == NULL))
 		return NULL;
 
-	if (is_kfence_address(object))
+	if (is_kfence_address(kasan_reset_tag(object)))
 		return (void *)object;
 
 	redzone_start = round_up((unsigned long)(object + size),
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 11c6e3650468..4fb8106f8e31 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -320,22 +320,28 @@ static inline u8 kasan_random_tag(void) { return 0; }
 
 static inline void kasan_poison(const void *address, size_t size, u8 value)
 {
+	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(kasan_reset_tag(address),
+	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)
 {
+	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(kasan_reset_tag(address),
-			round_up(size, KASAN_GRANULE_SIZE), get_tag(address));
+	hw_set_mem_tag_range((void *)address,
+			round_up(size, KASAN_GRANULE_SIZE), tag);
 }
 
 static inline bool kasan_byte_accessible(const void *addr)
-- 
2.30.0.365.g02bc693789-goog