[PATCH] fix sysfs node cpumap for large NR_CPUS

As pointed out by Paul Jackson <pj@sgi.com>, sometimes 99 chars is not enough.
We currently get a page from sysfs: that code should check we haven't overrun
it.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/base/node.c

@@ -21,9 +21,10 @@ static ssize_t node_read_cpumap(struct sys_device * dev, char * buf)
 	cpumask_t mask = node_dev->cpumap;
 	int len;
 
-	/* FIXME - someone should pass us a buffer size (count) or
-	 * use seq_file or something to avoid buffer overrun risk. */
-	len = cpumask_scnprintf(buf, 99 /* XXX FIXME */, mask);
+	/* 2004/06/03: buf currently PAGE_SIZE, need > 1 char per 4 bits. */
+	BUILD_BUG_ON(NR_CPUS/4 > PAGE_SIZE/2);
+
+	len = cpumask_scnprintf(buf, PAGE_SIZE-1, mask);
 	len += sprintf(buf + len, "\n");
 	return len;
 }

fs/sysfs/file.c

@@ -89,6 +89,7 @@ static int fill_read_buffer(struct file * file, struct sysfs_buffer * buffer)
 		return -ENOMEM;
 
 	count = ops->show(kobj,attr,buffer->page);
+	BUG_ON(count > PAGE_SIZE);
 	if (count >= 0)
 		buffer->count = count;
 	else