sunrpc: Fix reserved port range calculation

fsorenson · trondmypd · commit 5d71899a2663 · 2016-07-19T16:23:26.000-04:00
The range calculation for choosing the random reserved port will panic
with divide-by-zero when min_resvport == max_resvport, a range of one
port, not zero.

Fix the reserved port range calculation by adding one to the difference.

Signed-off-by: Frank Sorenson &lt;sorenson@redhat.com&gt;
Signed-off-by: Trond Myklebust &lt;trond.myklebust@primarydata.com&gt;
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
@@ -1714,7 +1714,7 @@ static void xs_udp_timer(struct rpc_xprt *xprt, struct rpc_task *task)
 
 static unsigned short xs_get_random_port(void)
 {
-	unsigned short range = xprt_max_resvport - xprt_min_resvport;
+	unsigned short range = xprt_max_resvport - xprt_min_resvport + 1;
 	unsigned short rand = (unsigned short) prandom_u32() % range;
 	return rand + xprt_min_resvport;
 }

Original file line number	Diff line number	Diff line change
`@@ -1714,7 +1714,7 @@ static void xs_udp_timer(struct rpc_xprt xprt, struct rpc_task task)`
`1714`	`1714`
`1715`	`1715`	`static unsigned short xs_get_random_port(void)`
`1716`	`1716`	`{`
`1717`		`- unsigned short range = xprt_max_resvport - xprt_min_resvport;`
	`1717`	`+ unsigned short range = xprt_max_resvport - xprt_min_resvport + 1;`
`1718`	`1718`	`unsigned short rand = (unsigned short) prandom_u32() % range;`
`1719`	`1719`	`return rand + xprt_min_resvport;`
`1720`	`1720`	`}`