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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, "yujuan.qi" <yujuan.qi@mediatek.com>,
        Paul Moore <paul@paul-moore.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.4 02/80] Cipso: cipso_v4_optptr enter infinite loop
Date:   Mon,  3 Sep 2018 18:48:40 +0200
Message-Id: <20180903164934.273092616@linuxfoundation.org>
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4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: yujuan.qi <yujuan.qi@mediatek.com>

commit 40413955ee265a5e42f710940ec78f5450d49149 upstream.

in for(),if((optlen > 0) && (optptr[1] == 0)), enter infinite loop.

Test: receive a packet which the ip length > 20 and the first byte of ip option is 0, produce this issue

Signed-off-by: yujuan.qi <yujuan.qi@mediatek.com>
Acked-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 net/ipv4/cipso_ipv4.c |   12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

--- a/net/ipv4/cipso_ipv4.c
+++ b/net/ipv4/cipso_ipv4.c
@@ -1593,9 +1593,17 @@ unsigned char *cipso_v4_optptr(const str
 	int taglen;
 
 	for (optlen = iph->ihl*4 - sizeof(struct iphdr); optlen > 0; ) {
-		if (optptr[0] == IPOPT_CIPSO)
+		switch (optptr[0]) {
+		case IPOPT_CIPSO:
 			return optptr;
-		taglen = optptr[1];
+		case IPOPT_END:
+			return NULL;
+		case IPOPT_NOOP:
+			taglen = 1;
+			break;
+		default:
+			taglen = optptr[1];
+		}
 		optlen -= taglen;
 		optptr += taglen;
 	}