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BACKPORT: FROMLIST: kasan: add memzero int for unaligned size at DEBUG

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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://lore.kernel.org/lkml/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>
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>

Bug: 193482732
Change-Id: Ie0f6a15637d212f5a273e13b7d271376c074cb91
Signed-off-by: Yee Lee <yee.lee@mediatek.com>
This commit is contained in:
Yee Lee
2021-07-13 13:39:59 +08:00
committed by Todd Kjos
parent 7acbce0bf4
commit 007213b1d0
1 changed files with 12 additions and 0 deletions
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12
mm/kasan/kasan.h
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@@ -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);