linux-kernel - [PATCH] Add nid sanity on alloc_pages

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Date:	Fri, 13 Jul 2007 10:45:07 +0800
From:	Joe Jin <joe.jin@...cle.com>
To:	akpm@...l.org, bill.irwin@...cle.com
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] Add nid sanity on alloc_pages_node

This patch add nid sanity check on alloc_pages_node().
While two process change nr_hugepages at a system, alloc_fresh_huge_page()
been called, at this function, nid defined as a static variable, but, there
is not any protection of, if 2 process called at the same time, maybe pass a
invalid nid to alloc_pages_node. 

We have hit it by following scripts:

#!/bin/bash
while : ; do 
	echo 1000000000000 > /proc/sys/vm/nr_hugepages 
	echo 1 > /proc/sys/vm/nr_hugepages 
	echo 10000000000000000000 > /proc/sys/vm/nr_hugepages 
	echo 0 > /proc/sys/vm/nr_hugepages 
done 


Run the script at _two_ difference terminal, after a short time, a kernel panic
info will print.


Signed-off-by: Joe Jin <joe.jin@...cle.com>
---

--- linux-2.6.22/include/linux/gfp.h.orig	2007-07-12 15:06:23.000000000 +0800
+++ linux-2.6.22/include/linux/gfp.h	2007-07-12 15:02:59.000000000 +0800
@@ -133,6 +133,9 @@
 	/* Unknown node is current node */
 	if (nid < 0)
 		nid = numa_node_id();
+	
+	if (unlikely(nid == MAX_NUMNODES))
+		nid = first_node(node_online_map);
 
 	return __alloc_pages(gfp_mask, order,
 		NODE_DATA(nid)->node_zonelists + gfp_zone(gfp_mask));
-
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