netdev - [PATCH v2 2/2] net: avoid infinite loop in mpls_gso_segment when mpls

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Message-Id: <85e04e1e6367f19c8f538d145b32f5bb93788d8a.1615199056.git.bnemeth@redhat.com>
Date:   Mon,  8 Mar 2021 11:31:26 +0100
From:   Balazs Nemeth <bnemeth@...hat.com>
To:     netdev@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, mst@...hat.com, jasowang@...hat.com,
        davem@...emloft.net, willemb@...gle.com,
        virtualization@...ts.linux-foundation.org, bnemeth@...hat.com
Subject: [PATCH v2 2/2] net: avoid infinite loop in mpls_gso_segment when mpls_hlen == 0

A packet with skb_inner_network_header(skb) == skb_network_header(skb)
and ETH_P_MPLS_UC will prevent mpls_gso_segment from pulling any headers
from the packet. Subsequently, the call to skb_mac_gso_segment will
again call mpls_gso_segment with the same packet leading to an infinite
loop.

Signed-off-by: Balazs Nemeth <bnemeth@...hat.com>
---
 net/mpls/mpls_gso.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/mpls/mpls_gso.c b/net/mpls/mpls_gso.c
index b1690149b6fa..cc1b6457fc93 100644
--- a/net/mpls/mpls_gso.c
+++ b/net/mpls/mpls_gso.c
@@ -27,7 +27,7 @@ static struct sk_buff *mpls_gso_segment(struct sk_buff *skb,
 
 	skb_reset_network_header(skb);
 	mpls_hlen = skb_inner_network_header(skb) - skb_network_header(skb);
-	if (unlikely(!pskb_may_pull(skb, mpls_hlen)))
+	if (unlikely(!mpls_hlen || !pskb_may_pull(skb, mpls_hlen)))
 		goto out;
 
 	/* Setup inner SKB. */
-- 
2.29.2