netdev - [PATCH net] net: openvswitch: ensure LSE is pullable before reading it

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Message-Id: <aa099f245d93218b84b5c056b67b6058ccf81a66.1606987185.git.dcaratti@redhat.com>
Date:   Thu,  3 Dec 2020 10:46:06 +0100
From:   Davide Caratti <dcaratti@...hat.com>
To:     Pravin B Shelar <pshelar@....org>,
        Jakub Kicinski <kuba@...nel.org>,
        John Hurley <john.hurley@...ronome.com>
Cc:     gnault@...hat.com, marcelo.leitner@...il.com,
        netdev@...r.kernel.org
Subject: [PATCH net] net: openvswitch: ensure LSE is pullable before reading it

when openvswitch is configured to mangle the LSE, the current value is
read from the packet dereferencing 4 bytes at mpls_hdr(): ensure that
the label is contained in the skb "linear" area.

Found by code inspection.

Fixes: d27cf5c59a12 ("net: core: add MPLS update core helper and use in OvS")
Signed-off-by: Davide Caratti <dcaratti@...hat.com>
---
 net/openvswitch/actions.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
index 5829a020b81c..c3a664871cb5 100644
--- a/net/openvswitch/actions.c
+++ b/net/openvswitch/actions.c
@@ -199,6 +199,9 @@ static int set_mpls(struct sk_buff *skb, struct sw_flow_key *flow_key,
 	__be32 lse;
 	int err;
 
+	if (!pskb_may_pull(skb, skb_network_offset(skb) + MPLS_HLEN))
+		return -ENOMEM;
+
 	stack = mpls_hdr(skb);
 	lse = OVS_MASKED(stack->label_stack_entry, *mpls_lse, *mask);
 	err = skb_mpls_update_lse(skb, lse);
-- 
2.28.0