linux-kernel - [PATCH] OOPS in identify_cpu() on CPUs without CPUID

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Date:	Sat, 8 Aug 2009 19:08:10 +0200
From:	Ondrej Zary <linux@...nbow-software.org>
To:	tglx@...utronix.de
Cc:	mingo@...hat.com, hpa@...or.com, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] OOPS in identify_cpu() on CPUs without CPUID

Kernel is broken for x86 CPUs without CPUID since 2.6.28. It crashes with NULL
pointer dereference in identify_cpu():

766        generic_identify(c);
767
768-->     if (this_cpu->c_identify)
769                this_cpu->c_identify(c);

this_cpu is NULL. This is because it's only initialized in get_cpu_vendor()
function, which is not called if the CPU has no CPUID instruction.

Signed-off-by: Ondrej Zary <linux@...nbow-software.org>

--- linux-2.6.30.4-orig/arch/x86/kernel/cpu/common.c	2009-06-10 05:05:27.000000000 +0200
+++ linux-2.6.30.4-router/arch/x86/kernel/cpu/common.c	2009-08-08 18:00:21.000000000 +0200
@@ -699,6 +699,7 @@
 
 static void __cpuinit generic_identify(struct cpuinfo_x86 *c)
 {
+	this_cpu = &default_cpu;
 	c->extended_cpuid_level = 0;
 
 	if (!have_cpuid_p())


-- 
Ondrej Zary
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