Messages in this thread | | | From | Andrey Ryabinin <> | Date | Wed, 8 Feb 2017 17:58:44 +0300 | Subject | Re: KASAN+netlink, was: [PATCH] [net-next?] hns: avoid stack overflow with CONFIG_KASAN |
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2017-02-08 16:10 GMT+03:00 Arnd Bergmann <arnd@arndb.de>: > On Wed, Feb 8, 2017 at 1:24 PM, Johannes Berg <johannes@sipsolutions.net> wrote:
> >> Btw, what's causing this to start with? Can't the compiler reuse the >> stack places? > > I have no idea. It's trying to find out of bounds accesses for > objects on the stack, so maybe it gives each variable a separate > stack location in order to see which one caused problems? >
If compiler cannot prove that access to the local variable is valid it will add redzones around that variable to be able to detect out of bounds accesses.
For example: static inline int nla_put_u8(struct sk_buff *skb, int attrtype, u8 value) { return nla_put(skb, attrtype, sizeof(u8), &value); } compiler will surround 'value' with redzones to catch potential oob access in nla_put().
Another way to fix this, would be something like this:
#ifdef CONFIG_KASAN /* don't bloat stack */ #define __noinline_for_kasan __noinline __maybe_unused #else #define __noinline_for_kasan inline #endif
static __noinline_for_kasan int nla_put_u8(struct sk_buff *skb, int attrtype, u8 value) { return nla_put(skb, attrtype, sizeof(u8), &value); }
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