udplite: Protection against coverage value wrap-around

This patch clamps the cscov setsockopt values to a maximum of 0xFFFF.

Setsockopt values greater than 0xffff can cause an unwanted
wrap-around.  Further, IPv6 jumbograms are not supported (RFC 3838,
3.5), so that values greater than 0xffff are not even useful.

Further changes: fixed a typo in the documentation.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index a751770..383d173 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1325,6 +1325,8 @@
 			return -ENOPROTOOPT;
 		if (val != 0 && val < 8) /* Illegal coverage: use default (8) */
 			val = 8;
+		else if (val > USHORT_MAX)
+			val = USHORT_MAX;
 		up->pcslen = val;
 		up->pcflag |= UDPLITE_SEND_CC;
 		break;
@@ -1337,6 +1339,8 @@
 			return -ENOPROTOOPT;
 		if (val != 0 && val < 8) /* Avoid silly minimal values.       */
 			val = 8;
+		else if (val > USHORT_MAX)
+			val = USHORT_MAX;
 		up->pcrlen = val;
 		up->pcflag |= UDPLITE_RECV_CC;
 		break;