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Date: Thu, 4 Jun 2020 10:03:59 -0400 From: Brian Gerst <brgerst@...il.com> To: linux-kernel@...r.kernel.org, x86@...nel.org Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>, "H . Peter Anvin" <hpa@...or.com>, Andy Lutomirski <luto@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Brian Gerst <brgerst@...il.com> Subject: [PATCH] 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@...il.com> --- arch/x86/include/asm/stackprotector.h | 12 ++++++++++++ arch/x86/kernel/smpboot.c | 12 +----------- arch/x86/xen/smp_pv.c | 2 -- 3 files changed, 13 insertions(+), 13 deletions(-) diff --git a/arch/x86/include/asm/stackprotector.h b/arch/x86/include/asm/stackprotector.h index 9804a7957f4e..7fb482f0f25b 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 2467f3dd35d3..dad7f9ca6478 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -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 ae4d0f283df3..e9f5d6ec30a6 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) base-commit: cc7a4a02564c6cc8dc981fb0a37313830ee8c2d4 -- 2.25.4
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