Commit c9a1ff31 authored by Brian Gerst's avatar Brian Gerst Committed by Borislav Petkov
Browse files

x86/stackprotector: Pre-initialize canary for secondary CPUs 



The idle tasks created for each secondary CPU already have a random stack
canary generated by fork().  Copy the canary to the percpu variable before
starting the secondary CPU which removes the need to call
boot_init_stack_canary().

Signed-off-by: default avatarBrian Gerst <brgerst@gmail.com>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200617225624.799335-1-brgerst@gmail.com
parent a5ce9f2b

arch/x86/include/asm/stackprotector.h

+12 −0
Original line number Diff line number Diff line
@@ -90,6 +90,15 @@ static __always_inline void boot_init_stack_canary(void) 
#endif

}



static inline void cpu_init_stack_canary(int cpu, struct task_struct *idle)

{

#ifdef CONFIG_X86_64

	per_cpu(fixed_percpu_data.stack_canary, cpu) = idle->stack_canary;

#else

	per_cpu(stack_canary.canary, cpu) = idle->stack_canary;

#endif

}



static inline void setup_stack_canary_segment(int cpu)

{

#ifdef CONFIG_X86_32
@@ -119,6 +128,9 @@ static inline void load_stack_canary_segment(void) 
static inline void setup_stack_canary_segment(int cpu)

{ }



static inline void cpu_init_stack_canary(int cpu, struct task_struct *idle)

{ }



static inline void load_stack_canary_segment(void)

{

#ifdef CONFIG_X86_32

arch/x86/kernel/smpboot.c

+2 −12
Original line number Diff line number Diff line
@@ -51,7 +51,6 @@ 
#include <linux/err.h>

#include <linux/nmi.h>

#include <linux/tboot.h>

#include <linux/stackprotector.h>

#include <linux/gfp.h>

#include <linux/cpuidle.h>

#include <linux/numa.h>
@@ -80,6 +79,7 @@ 
#include <asm/cpu_device_id.h>

#include <asm/spec-ctrl.h>

#include <asm/hw_irq.h>

#include <asm/stackprotector.h>



/* representing HT siblings of each logical CPU */

DEFINE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_sibling_map);
@@ -259,21 +259,10 @@ static void notrace start_secondary(void *unused) 
	/* enable local interrupts */

	local_irq_enable();



	/* to prevent fake stack check failure in clock setup */

	boot_init_stack_canary();



	x86_cpuinit.setup_percpu_clockev();



	wmb();

	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);



	/*

	 * Prevent tail call to cpu_startup_entry() because the stack protector

	 * guard has been changed a couple of function calls up, in

	 * boot_init_stack_canary() and must not be checked before tail calling

	 * another function.

	 */

	prevent_tail_call_optimization();

}



/**
@@ -1011,6 +1000,7 @@ int common_cpu_up(unsigned int cpu, struct task_struct *idle) 
	alternatives_enable_smp();



	per_cpu(current_task, cpu) = idle;

	cpu_init_stack_canary(cpu, idle);



	/* Initialize the interrupt stack(s) */

	ret = irq_init_percpu_irqstack(cpu);

arch/x86/xen/smp_pv.c

+0 −2
Original line number Diff line number Diff line
@@ -92,9 +92,7 @@ static void cpu_bringup(void) 
asmlinkage __visible void cpu_bringup_and_idle(void)

{

	cpu_bringup();

	boot_init_stack_canary();

	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);

	prevent_tail_call_optimization();

}



void xen_smp_intr_free_pv(unsigned int cpu)

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