[ 3.5.y.z extended stable ] Patch "fib_trie: remove potential out of bound access" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    fib_trie: remove potential out of bound access

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

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>From 5031ee91616da379705b4aad306b3a173620b8f6 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet at google.com>
Date: Mon, 5 Aug 2013 11:18:49 -0700
Subject: [PATCH] fib_trie: remove potential out of bound access

commit aab515d7c32a34300312416c50314e755ea6f765 upstream.

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 at google.com>
Signed-off-by: Eric Dumazet <edumazet at google.com>
Cc: Dmitry Vyukov <dvyukov at google.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.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 30b88d7..424704a 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>
@@ -1772,10 +1771,8 @@ 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;
--
1.8.3.2