Commit e8055139 authored by Ondrej Zary's avatar Ondrej Zary Committed by Ingo Molnar
Browse files

x86: Fix 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: default avatarOndrej Zary <linux@rainbow-software.org>
LKML-Reference: <200908112000.15993.linux@rainbow-software.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent fbd8b181

arch/x86/kernel/cpu/common.c

+24 −24
Original line number Diff line number Diff line
@@ -59,7 +59,30 @@ void __init setup_cpu_local_masks(void) 
	alloc_bootmem_cpumask_var(&cpu_sibling_setup_mask);

}



static const struct cpu_dev *this_cpu __cpuinitdata;

static void __cpuinit default_init(struct cpuinfo_x86 *c)

{

#ifdef CONFIG_X86_64

	display_cacheinfo(c);

#else

	/* Not much we can do here... */

	/* Check if at least it has cpuid */

	if (c->cpuid_level == -1) {

		/* No cpuid. It must be an ancient CPU */

		if (c->x86 == 4)

			strcpy(c->x86_model_id, "486");

		else if (c->x86 == 3)

			strcpy(c->x86_model_id, "386");

	}

#endif

}



static const struct cpu_dev __cpuinitconst default_cpu = {

	.c_init		= default_init,

	.c_vendor	= "Unknown",

	.c_x86_vendor	= X86_VENDOR_UNKNOWN,

};



static const struct cpu_dev *this_cpu __cpuinitdata = &default_cpu;



DEFINE_PER_CPU_PAGE_ALIGNED(struct gdt_page, gdt_page) = { .gdt = {

#ifdef CONFIG_X86_64
@@ -332,29 +355,6 @@ void switch_to_new_gdt(int cpu) 


static const struct cpu_dev *__cpuinitdata cpu_devs[X86_VENDOR_NUM] = {};



static void __cpuinit default_init(struct cpuinfo_x86 *c)

{

#ifdef CONFIG_X86_64

	display_cacheinfo(c);

#else

	/* Not much we can do here... */

	/* Check if at least it has cpuid */

	if (c->cpuid_level == -1) {

		/* No cpuid. It must be an ancient CPU */

		if (c->x86 == 4)

			strcpy(c->x86_model_id, "486");

		else if (c->x86 == 3)

			strcpy(c->x86_model_id, "386");

	}

#endif

}



static const struct cpu_dev __cpuinitconst default_cpu = {

	.c_init	= default_init,

	.c_vendor = "Unknown",

	.c_x86_vendor = X86_VENDOR_UNKNOWN,

};



static void __cpuinit get_model_name(struct cpuinfo_x86 *c)

{

	unsigned int *v;

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