[PATCH v2 1/1] kasan: Add memzero init for unaligned size under SLUB debug

[<yee.lee@mediatek.com>]

From: Yee Lee <yee.lee@mediatek.com>

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.

Signed-off-by: Yee Lee <yee.lee@mediatek.com>
---
 mm/kasan/kasan.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 8f450bc28045..d1054f35838f 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -387,6 +387,12 @@ static inline void kasan_unpoison(const void *addr, size_t size, bool init)
 
 	if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK))
 		return;
+#if IS_ENABLED(CONFIG_SLUB_DEBUG)
+	if (init && ((unsigned long)size & KASAN_GRANULE_MASK)) {
+		init = false;
+		memzero_explicit((void *)addr, size);
+	}
+#endif
 	size = round_up(size, KASAN_GRANULE_SIZE);
 
 	hw_set_mem_tag_range((void *)addr, size, tag, init);
-- 
2.18.0