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

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Message-ID: <1375726729.4457.45.camel@edumazet-glaptop>
Date:	Mon, 05 Aug 2013 11:18:49 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev <netdev@...r.kernel.org>,
	Andrey Konovalov <andreyknvl@...gle.com>,
	Dmitry Vyukov <dvyukov@...gle.com>
Subject: [PATCH] fib_trie: remove potential out of bound access

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>
---
 net/ipv4/fib_trie.c |    5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index 108a1e9c..3df6d3e 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -71,7 +71,6 @@
 #include <linux/init.h>
 #include <linux/list.h>
 #include <linux/slab.h>
-#include <linux/prefetch.h>
 #include <linux/export.h>
 #include <net/net_namespace.h>
 #include <net/ip.h>
@@ -1761,10 +1760,8 @@ static struct leaf *leaf_walk_rcu(struct tnode *p, struct rt_trie_node *c)
 			if (!c)
 				continue;
 
-			if (IS_LEAF(c)) {
-				prefetch(rcu_dereference_rtnl(p->child[idx]));
+			if (IS_LEAF(c))
 				return (struct leaf *) c;
-			}
 
 			/* Rescan start scanning in new node */
 			p = (struct tnode *) c;


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