[Xen-devel] [PATCH][cpufreq] add bounds checking to cpufreq_stats.c from upstream

["Mark Langsdorf" <mark.langsdorf@xxxxxxx>]

The cpufreq_stats.c will attempt to use an error return value as
an index to an array, causing the kernel to oops.  Stop that by
doing bounds checking.

This is a backport of upstream code.

Signed-off-by: Mark Langsdorf <mark.langsdorf@xxxxxxx>

-Mark Langsdorf
Operating System Research Center
AMD

diff -r cd744c5ec950 drivers/cpufreq/cpufreq_stats.c
--- a/drivers/cpufreq/cpufreq_stats.c   Wed Dec 12 10:18:35 2007 +0000
+++ b/drivers/cpufreq/cpufreq_stats.c   Wed Dec 12 18:02:54 2007 -0600
@@ -292,6 +292,9 @@ cpufreq_stat_notifier_trans (struct noti
        if (old_index == new_index)
                return 0;
 
+        if ((old_index < 0) || (new_index < 0))
+                return 0;
+
        spin_lock(&cpufreq_stats_lock);
        stat->last_index = new_index;
 #ifdef CONFIG_CPU_FREQ_STAT_DETAILS



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