Subject: [PATCH] division-by-zero in inet_csk_get_port

From: "Denis V. Lunev" <[email-masked]>
Date: Wed, 10 Oct 2007 12:55:30 +0400

This patch fixed a possible division-by-zero in inet_csk_get_port
treating situation low > high as if low == high.

Signed-off-by: Denis V. Lunev <[email-masked]>
CC: Antov Arapov  <[email-masked]>

--- ./net/ipv4/inet_connection_sock.c.getport	2007-10-09 15:16:02.000000000 +0400
+++ ./net/ipv4/inet_connection_sock.c	2007-10-10 12:44:04.000000000 +0400
@@ -80,7 +80,14 @@ int inet_csk_get_port(struct inet_hashin
 		int low = sysctl_local_port_range[0];
 		int high = sysctl_local_port_range[1];
 		int remaining = (high - low) + 1;
-		int rover = net_random() % (high - low) + low;
+		int rover;
+
+		/* Treat low > high as high == low */
+		if (remaining <= 1) {
+			remaining = 1;
+			rover = low;
+		} else
+			rover = net_random() % (high - low) + low;
 
 		do {
 			head = &hashinfo->bhash[inet_bhashfn(rover, hashinfo->bhash_size)];