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authorYee Lee <yee.lee@mediatek.com>2021-07-15 07:26:37 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2021-07-15 20:13:49 +0300
commit77a63c69ec43f4dc28f4b2d1c933c39e55de6ad8 (patch)
tree34ccc0e4a3508a8e4ef5689f9118d5dcd9592316
parent0d4a062af2cea33c2000b28420e8e2eb58b4fd0b (diff)
downloadlinux-77a63c69ec43f4dc28f4b2d1c933c39e55de6ad8.tar.xz
kasan: add memzero init for unaligned size at DEBUG
Issue: when SLUB debug is on, hwtag kasan_unpoison() would overwrite the redzone of object with unaligned size. An additional memzero_explicit() path is added to replacing init by hwtag instruction for those unaligned size at SLUB debug mode. The penalty is acceptable since they are only enabled in debug mode, not production builds. A block of comment is added for explanation. Link: https://lkml.kernel.org/r/20210705103229.8505-3-yee.lee@mediatek.com Signed-off-by: Yee Lee <yee.lee@mediatek.com> Suggested-by: Andrey Konovalov <andreyknvl@gmail.com> Suggested-by: Marco Elver <elver@google.com> Reviewed-by: Marco Elver <elver@google.com> Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com> Cc: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Nicholas Tang <nicholas.tang@mediatek.com> Cc: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com> Cc: Chinwen Chang <chinwen.chang@mediatek.com> Cc: Matthew Wilcox <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/kasan/kasan.h12
1 files changed, 12 insertions, 0 deletions
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 98e3059bfea4..d739cdd1621a 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -9,6 +9,7 @@
#ifdef CONFIG_KASAN_HW_TAGS
#include <linux/static_key.h>
+#include "../slab.h"
DECLARE_STATIC_KEY_FALSE(kasan_flag_stacktrace);
extern bool kasan_flag_async __ro_after_init;
@@ -387,6 +388,17 @@ static inline void kasan_unpoison(const void *addr, size_t size, bool init)
if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK))
return;
+ /*
+ * Explicitly initialize the memory with the precise object size to
+ * avoid overwriting the SLAB redzone. This disables initialization in
+ * the arch code and may thus lead to performance penalty. The penalty
+ * is accepted since SLAB redzones aren't enabled in production builds.
+ */
+ if (__slub_debug_enabled() &&
+ init && ((unsigned long)size & KASAN_GRANULE_MASK)) {
+ init = false;
+ memzero_explicit((void *)addr, size);
+ }
size = round_up(size, KASAN_GRANULE_SIZE);
hw_set_mem_tag_range((void *)addr, size, tag, init);