From: Geert Uytterhoeven <geert+renesas@glider.be>
Date: Mon, 22 Aug 2016 13:01:03 +0000 (+0200)
Subject: net: ipconfig: Fix NULL pointer dereference on RARP/BOOTP/DHCP timeout
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=1ae292a2457cd692828da2be87cb967260993ad0;p=openwrt%2Fstaging%2Fblogic.git

net: ipconfig: Fix NULL pointer dereference on RARP/BOOTP/DHCP timeout

If no RARP, BOOTP, or DHCP response is received, ic_dev is never set,
causing a NULL pointer dereference in ic_close_devs():

    Sending DHCP requests ...... timed out!
    Unable to handle kernel NULL pointer dereference at virtual address 00000004

To fix this, add a check to avoid dereferencing ic_dev if it is still
NULL.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Fixes: 2647cffb2bc6fbed ("net: ipconfig: Support using "delayed" DHCP replies")
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/ipv4/ipconfig.c b/net/ipv4/ipconfig.c
index ba9cbeafbb2e..071a785c65eb 100644
--- a/net/ipv4/ipconfig.c
+++ b/net/ipv4/ipconfig.c
@@ -306,7 +306,7 @@ static void __init ic_close_devs(void)
 	while ((d = next)) {
 		next = d->next;
 		dev = d->dev;
-		if (dev != ic_dev->dev && !netdev_uses_dsa(dev)) {
+		if ((!ic_dev || dev != ic_dev->dev) && !netdev_uses_dsa(dev)) {
 			pr_debug("IP-Config: Downing %s\n", dev->name);
 			dev_change_flags(dev, d->flags);
 		}