linux-kernel - [24/93] CPUFREQ: Fix use after free of struct powernow_k8

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Date:	Fri, 19 Feb 2010 08:29:17 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Thomas Renninger <trenn@...e.de>, Dave Jones <davej@...hat.com>
Subject: [24/93] CPUFREQ: Fix use after free of struct powernow_k8_data

2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Thomas Renninger <trenn@...e.de>

commit 557a701c16553b0b691dbb64ef30361115a80f64 upstream.

Easy fix for a regression introduced in 2.6.31.

On managed CPUs the cpufreq.c core will call driver->exit(cpu) on the
managed cpus and powernow_k8 will free the core's data.

Later driver->get(cpu) function might get called trying to read out the
current freq of a managed cpu and the NULL pointer check does not work on
the freed object -> better set it to NULL.

->get() is unsigned and must return 0 as invalid frequency.

Reference:
http://bugzilla.kernel.org/show_bug.cgi?id=14391

Signed-off-by: Thomas Renninger <trenn@...e.de>
Tested-by: Michal Schmidt <mschmidt@...hat.com>
Signed-off-by: Dave Jones <davej@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 arch/x86/kernel/cpu/cpufreq/powernow-k8.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/x86/kernel/cpu/cpufreq/powernow-k8.c
+++ b/arch/x86/kernel/cpu/cpufreq/powernow-k8.c
@@ -1351,6 +1351,7 @@ static int __devexit powernowk8_cpu_exit
 
 	kfree(data->powernow_table);
 	kfree(data);
+	per_cpu(powernow_data, pol->cpu) = NULL;
 
 	return 0;
 }
@@ -1370,7 +1371,7 @@ static unsigned int powernowk8_get(unsig
 	int err;
 
 	if (!data)
-		return -EINVAL;
+		return 0;
 
 	smp_call_function_single(cpu, query_values_on_cpu, &err, true);
 	if (err)


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