Messages in this thread | | | Date | Tue, 8 Sep 2015 12:36:24 +0300 | Subject | Re: [PATCH] kasan: fix last shadow judgement in memory_is_poisoned_16() | From | Andrey Ryabinin <> |
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2015-09-08 4:42 GMT+03:00 Xishi Qiu <qiuxishi@huawei.com>: > The shadow which correspond 16 bytes may span 2 or 3 bytes. If shadow > only take 2 bytes, we can return in "if (likely(!last_byte)) ...", but > it calculates wrong, so fix it. >
Please, be more specific. Describe what is wrong with the current code and why, what's the effect of this bug and how you fixed it.
> Signed-off-by: Xishi Qiu <qiuxishi@huawei.com> > --- > mm/kasan/kasan.c | 3 +-- > 1 files changed, 1 insertions(+), 2 deletions(-) > > diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c > index 7b28e9c..8da2114 100644 > --- a/mm/kasan/kasan.c > +++ b/mm/kasan/kasan.c > @@ -135,12 +135,11 @@ static __always_inline bool memory_is_poisoned_16(unsigned long addr) > > if (unlikely(*shadow_addr)) { > u16 shadow_first_bytes = *(u16 *)shadow_addr; > - s8 last_byte = (addr + 15) & KASAN_SHADOW_MASK; > > if (unlikely(shadow_first_bytes)) > return true; > > - if (likely(!last_byte)) > + if (likely(IS_ALIGNED(addr, 8))) > return false; > > return memory_is_poisoned_1(addr + 15); > -- > 1.7.1 > >
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