net: ipconfig: fix use after free

ic_close_devs() calls kfree() for all devices's ic_device. Since commit
2647cff ("net: ipconfig: Support using "delayed" DHCP replies")
the active device's ic_device is still used however to print the
ipconfig summary which results in an oops if the memory is already
changed. So delay freeing until after the autoconfig results are
reported.

Fixes: 2647cff ("net: ipconfig: Support using "delayed" DHCP replies")
Reported-by: Geert Uytterhoeven <[email protected]>
Signed-off-by: Uwe Kleine-König <[email protected]>
Tested-by: Geert Uytterhoeven <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

Author: Uwe Kleine-König

net/ipv4/ipconfig.c

@@ -1492,14 +1492,6 @@ static int __init ip_auto_config(void)
 	if (ic_defaults() < 0)
 		return -1;
 
-	/*
-	 * Close all network devices except the device we've
-	 * autoconfigured and set up routes.
-	 */
-	ic_close_devs();
-	if (ic_setup_if() < 0 || ic_setup_routes() < 0)
-		return -1;
-
 	/*
 	 * Record which protocol was actually used.
 	 */
@@ -1534,6 +1526,15 @@ static int __init ip_auto_config(void)
 	pr_cont("\n");
 #endif /* !SILENT */
 
+	/*
+	 * Close all network devices except the device we've
+	 * autoconfigured and set up routes.
+	 */
+	ic_close_devs();
+	if (ic_setup_if() < 0 || ic_setup_routes() < 0)
+		return -1;
+
+
 	return 0;
 }