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From: Lizhi Xu <lizhi.xu@windriver.com>
To: <syzbot+99d15fcdb0132a1e1a82@syzkaller.appspotmail.com>
CC: <davem@davemloft.net>, <dsahern@kernel.org>, <edumazet@google.com>,
        <fw@strlen.de>, <horms@kernel.org>, <kuba@kernel.org>,
        <linux-kernel@vger.kernel.org>, <netdev@vger.kernel.org>,
        <pabeni@redhat.com>, <syzkaller-bugs@googlegroups.com>
Subject: [PATCH net-next] net/mpls: fix WARNING in mpls_gso_segment
Date: Thu, 22 Feb 2024 12:00:45 +0800
Message-ID: <20240222040046.2568269-1-lizhi.xu@windriver.com>
In-Reply-To: <00000000000043b1310611e388aa@google.com>
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When the network header pointer is greater than the inner network header, the
difference between the two can cause mpls_hlen overflow.

Reported-and-tested-by: syzbot+99d15fcdb0132a1e1a82@syzkaller.appspotmail.com
Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
---
 net/mpls/mpls_gso.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/mpls/mpls_gso.c b/net/mpls/mpls_gso.c
index 533d082f0701..2ab24b2fd90f 100644
--- a/net/mpls/mpls_gso.c
+++ b/net/mpls/mpls_gso.c
@@ -25,11 +25,11 @@ static struct sk_buff *mpls_gso_segment(struct sk_buff *skb,
 	netdev_features_t mpls_features;
 	u16 mac_len = skb->mac_len;
 	__be16 mpls_protocol;
-	unsigned int mpls_hlen;
+	int mpls_hlen;
 
 	skb_reset_network_header(skb);
 	mpls_hlen = skb_inner_network_header(skb) - skb_network_header(skb);
-	if (unlikely(!mpls_hlen || mpls_hlen % MPLS_HLEN))
+	if (unlikely(mpls_hlen <= 0 || mpls_hlen % MPLS_HLEN))
 		goto out;
 	if (unlikely(!pskb_may_pull(skb, mpls_hlen)))
 		goto out;
-- 
2.43.0