[PATCH 4.9 050/107] Cipso: cipso_v4_optptr enter infinite loop

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: yujuan.qi <yujuan.qi@xxxxxxxxxxxx>

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@xxxxxxxxxxxx>
Acked-by: Paul Moore <paul@xxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 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
@@ -1523,9 +1523,17 @@ 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;
 	}