linux-kernel - [PATCH 4.1 137/159] sched: cls_bpf: fix panic on filter replace

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Date:	Sat, 26 Sep 2015 13:56:23 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Daniel Borkmann <daniel@...earbox.net>,
	John Fastabend <john.r.fastabend@...el.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.1 137/159] sched: cls_bpf: fix panic on filter replace

4.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Daniel Borkmann <daniel@...earbox.net>

[ Upstream commit f6bfc46da6292b630ba389592123f0dd02066172 ]

The following test case causes a NULL pointer dereference in cls_bpf:

  FOO="1,6 0 0 4294967295,"
  tc filter add dev foo parent 1: bpf bytecode "$FOO" flowid 1:1 action ok
  tc filter replace dev foo parent 1: pref 49152 handle 0x1 \
            bpf bytecode "$FOO" flowid 1:1 action drop

The problem is that commit 1f947bf151e9 ("net: sched: rcu'ify cls_bpf")
accidentally swapped the arguments of list_replace_rcu(), the old
element needs to be the first argument and the new element the second.

Fixes: 1f947bf151e9 ("net: sched: rcu'ify cls_bpf")
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Acked-by: John Fastabend <john.r.fastabend@...el.com>
Acked-by: Alexei Starovoitov <ast@...mgrid.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/sched/cls_bpf.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/sched/cls_bpf.c
+++ b/net/sched/cls_bpf.c
@@ -364,7 +364,7 @@ static int cls_bpf_change(struct net *ne
 		goto errout;
 
 	if (oldprog) {
-		list_replace_rcu(&prog->link, &oldprog->link);
+		list_replace_rcu(&oldprog->link, &prog->link);
 		tcf_unbind_filter(tp, &oldprog->res);
 		call_rcu(&oldprog->rcu, __cls_bpf_delete_prog);
 	} else {


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