x86, UV: Use allocated buffer in tlb_uv.c:tunables_read()

The original code didn't check that the value returned from
snprintf() was less than the size of the buffer.  Although it
didn't cause a runtime bug in this case, it makes the static
checkers complain.

Andrew Morton suggested a dynamically sized buffer would be
cleaner.
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dan Carpenter <error27@gmail.com>
Cc: Cliff Wickman <cpw@sgi.com>
Cc: Jack Steiner <steiner@sgi.com>
Cc: Robin Holt <holt@sgi.com>
LKML-Reference: <20100929083118.GA6376@bicker>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/tlb_uv.c

@@ -1001,10 +1001,10 @@ static int uv_ptc_seq_show(struct seq_file *file, void *data)
 static ssize_t tunables_read(struct file *file, char __user *userbuf,
 						size_t count, loff_t *ppos)
 {
-	char buf[300];
+	char *buf;
 	int ret;
 
-	ret = snprintf(buf, 300, "%s %s %s\n%d %d %d %d %d %d %d %d %d\n",
+	buf = kasprintf(GFP_KERNEL, "%s %s %s\n%d %d %d %d %d %d %d %d %d\n",
 		"max_bau_concurrent plugged_delay plugsb4reset",
 		"timeoutsb4reset ipi_reset_limit complete_threshold",
 		"congested_response_us congested_reps congested_period",
@@ -1012,7 +1012,12 @@ static ssize_t tunables_read(struct file *file, char __user *userbuf,
 		timeoutsb4reset, ipi_reset_limit, complete_threshold,
 		congested_response_us, congested_reps, congested_period);
 
-	return simple_read_from_buffer(userbuf, count, ppos, buf, ret);
+	if (!buf)
+		return -ENOMEM;
+
+	ret = simple_read_from_buffer(userbuf, count, ppos, buf, strlen(buf));
+	kfree(buf);
+	return ret;
 }
 
 /*