NFSv4: limit lease period in nfs4_set_lease_period()

In nfs4_set_lease_period(), the passed 32-bit lease period in seconds is
multiplied by HZ -- that might overflow before being implicitly cast to
*unsigned long* (32/64-bit type), while initializing the lease variable.
Cap the lease period at MAX_LEASE_PERIOD (#define'd to 1 hour for now),
before multipying to avoid such overflow...

Found by Linux Verification Center (linuxtesting.org) with the Svace static
analysis tool.

Signed-off-by: Sergey Shtylyov <[e-mail]>
Suggested-by: Trond Myklebust <[e-mail]>
Signed-off-by: Anna Schumaker <[e-mail]>

fs/nfs/nfs4renewd.c

···
 	cancel_delayed_work_sync(&clp->cl_renewd);
 }
 
+#define MAX_LEASE_PERIOD (60 * 60)	/* 1 hour */
+
 /**
  * nfs4_set_lease_period - Sets the lease period on a nfs_client
  *
···
  */
 void nfs4_set_lease_period(struct nfs_client *clp, u32 period)
 {
-	unsigned long lease = period * HZ;
+	unsigned long lease;
+
+	/* Limit the lease period */
+	if (period < MAX_LEASE_PERIOD)
+		lease = period * HZ;
+	else
+		lease = MAX_LEASE_PERIOD * HZ;
 
 	spin_lock(&clp->cl_lock);
 	clp->cl_lease_time = lease;