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From: Shreyansh Chouhan <chouhan.shreyansh630@gmail.com>
To: davem@davemloft.net, yoshfuji@linux-ipv6.org, dsahern@kernel.org,
	kuba@kernel.org, willemdebruijn.kernel@gmail.com
Cc: Shreyansh Chouhan <chouhan.shreyansh630@gmail.com>,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	syzbot+ff8e1b9f2f36481e2efc@syzkaller.appspotmail.com
Subject: [PATCH] ip_gre/ip6_gre: add check for invalid csum_start
Date: Thu, 19 Aug 2021 20:04:47 +0530	[thread overview]
Message-ID: <20210819143447.314539-1-chouhan.shreyansh630@gmail.com> (raw)

If we get a ip gre packet with TUNNEL_CSUM set, an invalid csum_start
value causes skb->csum_start offset to be less than the offset for
skb->data after we pull the ip header from the packet during the
ipgre_xmit call.

This patch adds a sanity check to gre_handle_offloads, which checks the
validity of skb->csum_start after we have pulled the ip header from the
packet in the ipgre_xmit call.

Reported-by: syzbot+ff8e1b9f2f36481e2efc@syzkaller.appspotmail.com
Signed-off-by: Shreyansh Chouhan <chouhan.shreyansh630@gmail.com>
---
 net/ipv4/ip_gre.c  | 2 ++
 net/ipv6/ip6_gre.c | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index 12dca0c85f3c..95419b7adf5c 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -473,6 +473,8 @@ static void __gre_xmit(struct sk_buff *skb, struct net_device *dev,
 
 static int gre_handle_offloads(struct sk_buff *skb, bool csum)
 {
+	if (csum && skb_checksum_start(skb) < skb->data)
+		return -EINVAL;
 	return iptunnel_handle_offloads(skb, csum ? SKB_GSO_GRE_CSUM : SKB_GSO_GRE);
 }
 
diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index bc224f917bbd..7a5e90e09363 100644
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -629,6 +629,8 @@ static int gre_rcv(struct sk_buff *skb)
 
 static int gre_handle_offloads(struct sk_buff *skb, bool csum)
 {
+	if (csum && skb_checksum_start(skb) < skb->data)
+		return -EINVAL;
 	return iptunnel_handle_offloads(skb,
 					csum ? SKB_GSO_GRE_CSUM : SKB_GSO_GRE);
 }
-- 
2.31.1


             reply	other threads:[~2021-08-19 14:35 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-19 14:34 Shreyansh Chouhan [this message]
2021-08-19 16:56 ` Willem de Bruijn
2021-08-19 17:04   ` Jakub Kicinski
2021-08-21  7:14     ` [PATCH 1/2 net] ip_gre: add validation for csum_start Shreyansh Chouhan
2021-08-21 13:41       ` Willem de Bruijn
2021-09-01 11:53         ` Ido Schimmel
2021-09-01 13:46           ` Willem de Bruijn
2021-09-01 15:53             ` Ido Schimmel
2021-09-01 21:39               ` Willem de Bruijn
2021-08-22 20:30       ` patchwork-bot+netdevbpf
2021-08-21  7:14     ` [PATCH 2/2 net] ip6_gre: " Shreyansh Chouhan
2021-08-21 13:42       ` Willem de Bruijn
2021-08-21  7:18     ` [PATCH] ip_gre/ip6_gre: add check for invalid csum_start Shreyansh Chouhan
2021-08-21 13:44       ` Willem de Bruijn

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