netdev - Re: [PATCH] fib_trie: remove potential out of bound access

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Message-ID: <20130805154111.119ac5ac@nehalam.linuxnetplumber.net>
Date:	Mon, 5 Aug 2013 15:41:11 -0700
From:	Stephen Hemminger <stephen@...workplumber.org>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Andrey Konovalov <andreyknvl@...gle.com>,
	Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH] fib_trie: remove potential out of bound access

On Mon, 05 Aug 2013 11:18:49 -0700
Eric Dumazet <eric.dumazet@...il.com> wrote:

> From: Eric Dumazet <edumazet@...gle.com>
> 
> AddressSanitizer [1] dynamic checker pointed a potential
> out of bound access in leaf_walk_rcu()
> 
> We could allocate one more slot in tnode_new() to leave the prefetch()
> in-place but it looks not worth the pain.
> 
> Bug added in commit 82cfbb008572b ("[IPV4] fib_trie: iterator recode")
> 
> [1] :
> https://code.google.com/p/address-sanitizer/wiki/AddressSanitizerForKernel
> 
> Reported-by: Andrey Konovalov <andreyknvl@...gle.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Dmitry Vyukov <dvyukov@...gle.com>

Isn't prefetch supposed to always be safe, even out of bounds; even prefetch(NULL).
Although I really doubt prefetch helps in in this code anyway.

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