The following commit has been merged into the x86/cpu branch of tip: Commit-ID: c9a1ff316bc9b1d1806a4366d0aef6e18833ba52 Gitweb: https://git.kernel.org/tip/c9a1ff316bc9b1d1806a4366d0aef6e18833ba52 Author: Brian Gerst <brgerst@xxxxxxxxx> AuthorDate: Wed, 17 Jun 2020 18:56:24 -04:00 Committer: Borislav Petkov <bp@xxxxxxx> CommitterDate: Thu, 18 Jun 2020 13:09:17 +02:00 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: Brian Gerst <brgerst@xxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Link: https://lkml.kernel.org/r/20200617225624.799335-1-brgerst@xxxxxxxxx --- arch/x86/include/asm/stackprotector.h | 12 ++++++++++++ arch/x86/kernel/smpboot.c | 14 ++------------ arch/x86/xen/smp_pv.c | 2 -- 3 files changed, 14 insertions(+), 14 deletions(-) diff --git a/arch/x86/include/asm/stackprotector.h b/arch/x86/include/asm/stackprotector.h index 9804a79..7fb482f 100644 --- a/arch/x86/include/asm/stackprotector.h +++ b/arch/x86/include/asm/stackprotector.h @@ -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 diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index ffbd9a3..a11bd53 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -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); diff --git a/arch/x86/xen/smp_pv.c b/arch/x86/xen/smp_pv.c index 171aff1..9ea598d 100644 --- a/arch/x86/xen/smp_pv.c +++ b/arch/x86/xen/smp_pv.c @@ -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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