linux-kernel - [patch] numa: fix BUILD_BUG_ON for node_read

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Date:	Wed, 10 Mar 2010 14:50:21 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Greg Kroah-Hartman <gregkh@...e.de>
cc:	linux-kernel@...r.kernel.org
Subject: [patch] numa: fix BUILD_BUG_ON for node_read_distance

node_read_distance() has a BUILD_BUG_ON() to prevent buffer overruns when
the number of nodes printed will exceed the buffer length.

Each node only needs four chars: three for distance (maximum distance is
255) and one for a seperating space or a trailing newline.

Signed-off-by: David Rientjes <rientjes@...gle.com>
---
 drivers/base/node.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/base/node.c b/drivers/base/node.c
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -165,8 +165,11 @@ static ssize_t node_read_distance(struct sys_device * dev,
 	int len = 0;
 	int i;
 
-	/* buf currently PAGE_SIZE, need ~4 chars per node */
-	BUILD_BUG_ON(MAX_NUMNODES*4 > PAGE_SIZE/2);
+	/*
+	 * buf is currently PAGE_SIZE in length and each node needs 4 chars
+	 * at the most (distance + space or newline).
+	 */
+	BUILD_BUG_ON(MAX_NUMNODES*4 > PAGE_SIZE);
 
 	for_each_online_node(i)
 		len += sprintf(buf + len, "%s%d", i ? " " : "", node_distance(nid, i));
--
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