Re: [PATCH v2 1/1] kasan: Add memzero init for unaligned size under SLUB debug
From: Andrey Konovalov <andreyknvl@gmail.com>
Date: 2021-06-25 14:03:50
Also in:
linux-arm-kernel, linux-mm, lkml
On Thu, Jun 24, 2021 at 2:26 PM [off-list ref] wrote:
quoted hunk ↗ jump to hunk
From: Yee Lee <redacted> 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 <redacted> --- 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)
Is this an issue only with SLUB? SLAB also uses redzones.
+ if (init && ((unsigned long)size & KASAN_GRANULE_MASK)) {This needs a comment along the lines of: /* 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. */
+ 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);
--
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