linux-kernel - [PATCH] netconsole: avoid null pointer dereference at show_local

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Message-ID: <47B55F4C.5080703@bx.jp.nec.com>
Date:	Fri, 15 Feb 2008 18:45:48 +0900
From:	Keiichi KII <k-keiichi@...jp.nec.com>
To:	Matt Mackall <mpm@...enic.com>
CC:	Satyam Sharma <satyam.sharma@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Netdev <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	Stephen Hemminger <shemminger@...ux-foundation.org>
Subject: [PATCH] netconsole: avoid null pointer dereference at show_local_mac()

From: Keiichi KII <k-keiichi@...jp.nec.com>

This patch avoids a null pointer dereference when we read local_mac 
for netconsole in configfs and shows default local mac address
value.

A null pointer dereference occurs when we call show_local_mac() via 
local_mac entry in configfs before we setup the content of netpoll
using netpoll_setup().

This patch is for 2.6.25-rc1.
Your comments are very welcome.

Signed-off-by: Keiichi KII <k-keiichi@...jp.nec.com>
---
Index: pre-release/drivers/net/netconsole.c
===================================================================
--- pre-release.orig/drivers/net/netconsole.c
+++ pre-release/drivers/net/netconsole.c
@@ -309,8 +309,8 @@ static ssize_t show_local_mac(struct net
 	struct net_device *dev = nt->np.dev;
 
 	DECLARE_MAC_BUF(mac);
-	return snprintf(buf, PAGE_SIZE, "%s\n",
-			print_mac(mac, dev->dev_addr));
+	return snprintf(buf, PAGE_SIZE, "%s\n", dev ?
+			print_mac(mac, dev->dev_addr) : "ff:ff:ff:ff:ff:ff");
 }
 
 static ssize_t show_remote_mac(struct netconsole_target *nt, char *buf)

-- 
Keiichi KII
NEC Corporation OSS Platform Development Division
E-mail: k-keiichi@...jp.nec.com

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