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

Greg Kroah-Hartman
2015-09-26T21:26:39Z

From: Daniel Borkmann <daniel@iogearbox.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@iogearbox.net>
Acked-by: John Fastabend <john.r.fastabend@intel.com>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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 {