Re: [PATCH 2/2] openvswitch: Fix condition check in output_userspace() by using nla_ok()
From: Pravin Shelar <hidden>
Date: 2021-09-21 20:54:58
Also in:
lkml
On Fri, Sep 17, 2021 at 1:25 AM Jiasheng Jiang [off-list ref] wrote:
Just using 'rem > 0' might be unsafe, so it's better
to use the nla_ok() instead.
Because we can see from the nla_next() that
'*remaining' might be smaller than 'totlen'. And nla_ok()
will avoid it happening.
For example, ovs_dp_process_packet() -> ovs_execute_actions()
-> do_execute_actions() -> output_userspace(), and attr comes
from OVS_CB(skb)->input_vport,which restores the received packet
from the user space.
Fixes: ccb1352e76cff0524e7ccb2074826a092dd13016
('net: Add Open vSwitch kernel components.')
Signed-off-by: Jiasheng Jiang <redacted>quoted hunk ↗ jump to hunk
--- net/openvswitch/actions.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c index c23537f..e8236dd 100644 --- a/net/openvswitch/actions.c +++ b/net/openvswitch/actions.c@@ -915,8 +915,7 @@ static int output_userspace(struct datapath *dp, struct sk_buff *skb, upcall.cmd = OVS_PACKET_CMD_ACTION; upcall.mru = OVS_CB(skb)->mru; - for (a = nla_data(attr), rem = nla_len(attr); rem > 0; - a = nla_next(a, &rem)) { + nla_for_each_nested(a, attr, rem) { switch (nla_type(a)) { case OVS_USERSPACE_ATTR_USERDATA: upcall.userdata = a;
These nl-attributes are built and verified at time of OVS flow install, so the rest of checks in nla_ok, is not required.