From 33e45234987ea3ed4b05fc512f4441696478f12d Mon Sep 17 00:00:00 2001 From: Kristina Martsenko Date: Fri, 13 Mar 2020 14:34:56 +0530 Subject: [PATCH] arm64: initialize and switch ptrauth kernel keys Set up keys to use pointer authentication within the kernel. The kernel will be compiled with APIAKey instructions, the other keys are currently unused. Each task is given its own APIAKey, which is initialized during fork. The key is changed during context switch and on kernel entry from EL0. The keys for idle threads need to be set before calling any C functions, because it is not possible to enter and exit a function with different keys. Reviewed-by: Kees Cook Reviewed-by: Catalin Marinas Reviewed-by: Vincenzo Frascino Signed-off-by: Kristina Martsenko [Amit: Modified secondary cores key structure, comments] Signed-off-by: Amit Daniel Kachhap Signed-off-by: Catalin Marinas --- arch/arm64/include/asm/asm_pointer_auth.h | 14 ++++++++++++++ arch/arm64/include/asm/pointer_auth.h | 13 +++++++++++++ arch/arm64/include/asm/processor.h | 1 + arch/arm64/include/asm/smp.h | 4 ++++ arch/arm64/kernel/asm-offsets.c | 5 +++++ arch/arm64/kernel/entry.S | 3 +++ arch/arm64/kernel/process.c | 2 ++ arch/arm64/kernel/smp.c | 8 ++++++++ arch/arm64/mm/proc.S | 12 ++++++++++++ 9 files changed, 62 insertions(+) diff --git a/arch/arm64/include/asm/asm_pointer_auth.h b/arch/arm64/include/asm/asm_pointer_auth.h index 3482348..d3f4aee 100644 --- a/arch/arm64/include/asm/asm_pointer_auth.h +++ b/arch/arm64/include/asm/asm_pointer_auth.h @@ -39,11 +39,25 @@ alternative_if ARM64_HAS_GENERIC_AUTH alternative_else_nop_endif .endm + .macro ptrauth_keys_install_kernel tsk, tmp1, tmp2, tmp3 +alternative_if ARM64_HAS_ADDRESS_AUTH + mov \tmp1, #THREAD_KEYS_KERNEL + add \tmp1, \tsk, \tmp1 + ldp \tmp2, \tmp3, [\tmp1, #PTRAUTH_KERNEL_KEY_APIA] + msr_s SYS_APIAKEYLO_EL1, \tmp2 + msr_s SYS_APIAKEYHI_EL1, \tmp3 + isb +alternative_else_nop_endif + .endm + #else /* CONFIG_ARM64_PTR_AUTH */ .macro ptrauth_keys_install_user tsk, tmp1, tmp2, tmp3 .endm + .macro ptrauth_keys_install_kernel tsk, tmp1, tmp2, tmp3 + .endm + #endif /* CONFIG_ARM64_PTR_AUTH */ #endif /* __ASM_ASM_POINTER_AUTH_H */ diff --git a/arch/arm64/include/asm/pointer_auth.h b/arch/arm64/include/asm/pointer_auth.h index dabe026..aa956ca 100644 --- a/arch/arm64/include/asm/pointer_auth.h +++ b/arch/arm64/include/asm/pointer_auth.h @@ -30,6 +30,10 @@ struct ptrauth_keys_user { struct ptrauth_key apga; }; +struct ptrauth_keys_kernel { + struct ptrauth_key apia; +}; + static inline void ptrauth_keys_init_user(struct ptrauth_keys_user *keys) { if (system_supports_address_auth()) { @@ -50,6 +54,12 @@ do { \ write_sysreg_s(__pki_v.hi, SYS_ ## k ## KEYHI_EL1); \ } while (0) +static inline void ptrauth_keys_init_kernel(struct ptrauth_keys_kernel *keys) +{ + if (system_supports_address_auth()) + get_random_bytes(&keys->apia, sizeof(keys->apia)); +} + extern int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg); /* @@ -66,11 +76,14 @@ static inline unsigned long ptrauth_strip_insn_pac(unsigned long ptr) #define ptrauth_thread_init_user(tsk) \ ptrauth_keys_init_user(&(tsk)->thread.keys_user) +#define ptrauth_thread_init_kernel(tsk) \ + ptrauth_keys_init_kernel(&(tsk)->thread.keys_kernel) #else /* CONFIG_ARM64_PTR_AUTH */ #define ptrauth_prctl_reset_keys(tsk, arg) (-EINVAL) #define ptrauth_strip_insn_pac(lr) (lr) #define ptrauth_thread_init_user(tsk) +#define ptrauth_thread_init_kernel(tsk) #endif /* CONFIG_ARM64_PTR_AUTH */ #endif /* __ASM_POINTER_AUTH_H */ diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h index 496a928..4c77da5 100644 --- a/arch/arm64/include/asm/processor.h +++ b/arch/arm64/include/asm/processor.h @@ -147,6 +147,7 @@ struct thread_struct { struct debug_info debug; /* debugging */ #ifdef CONFIG_ARM64_PTR_AUTH struct ptrauth_keys_user keys_user; + struct ptrauth_keys_kernel keys_kernel; #endif }; diff --git a/arch/arm64/include/asm/smp.h b/arch/arm64/include/asm/smp.h index 8d66497..40d5ba0 100644 --- a/arch/arm64/include/asm/smp.h +++ b/arch/arm64/include/asm/smp.h @@ -38,6 +38,7 @@ #include #include #include +#include DECLARE_PER_CPU_READ_MOSTLY(int, cpu_number); @@ -95,6 +96,9 @@ asmlinkage void secondary_start_kernel(void); struct secondary_data { void *stack; struct task_struct *task; +#ifdef CONFIG_ARM64_PTR_AUTH + struct ptrauth_keys_kernel ptrauth_key; +#endif long status; }; diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c index 7b1ea2a..9981a0a 100644 --- a/arch/arm64/kernel/asm-offsets.c +++ b/arch/arm64/kernel/asm-offsets.c @@ -42,6 +42,7 @@ int main(void) DEFINE(THREAD_CPU_CONTEXT, offsetof(struct task_struct, thread.cpu_context)); #ifdef CONFIG_ARM64_PTR_AUTH DEFINE(THREAD_KEYS_USER, offsetof(struct task_struct, thread.keys_user)); + DEFINE(THREAD_KEYS_KERNEL, offsetof(struct task_struct, thread.keys_kernel)); #endif BLANK(); DEFINE(S_X0, offsetof(struct pt_regs, regs[0])); @@ -91,6 +92,9 @@ int main(void) BLANK(); DEFINE(CPU_BOOT_STACK, offsetof(struct secondary_data, stack)); DEFINE(CPU_BOOT_TASK, offsetof(struct secondary_data, task)); +#ifdef CONFIG_ARM64_PTR_AUTH + DEFINE(CPU_BOOT_PTRAUTH_KEY, offsetof(struct secondary_data, ptrauth_key)); +#endif BLANK(); #ifdef CONFIG_KVM_ARM_HOST DEFINE(VCPU_CONTEXT, offsetof(struct kvm_vcpu, arch.ctxt)); @@ -137,6 +141,7 @@ int main(void) DEFINE(PTRAUTH_USER_KEY_APDA, offsetof(struct ptrauth_keys_user, apda)); DEFINE(PTRAUTH_USER_KEY_APDB, offsetof(struct ptrauth_keys_user, apdb)); DEFINE(PTRAUTH_USER_KEY_APGA, offsetof(struct ptrauth_keys_user, apga)); + DEFINE(PTRAUTH_KERNEL_KEY_APIA, offsetof(struct ptrauth_keys_kernel, apia)); BLANK(); #endif return 0; diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 684e475..3dad2d0 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -178,6 +178,7 @@ alternative_cb_end apply_ssbd 1, x22, x23 + ptrauth_keys_install_kernel tsk, x20, x22, x23 .else add x21, sp, #S_FRAME_SIZE get_current_task tsk @@ -342,6 +343,7 @@ alternative_else_nop_endif msr cntkctl_el1, x1 4: #endif + /* No kernel C function calls after this as user keys are set. */ ptrauth_keys_install_user tsk, x0, x1, x2 apply_ssbd 0, x0, x1 @@ -898,6 +900,7 @@ ENTRY(cpu_switch_to) ldr lr, [x8] mov sp, x9 msr sp_el0, x1 + ptrauth_keys_install_kernel x1, x8, x9, x10 ret ENDPROC(cpu_switch_to) NOKPROBE(cpu_switch_to) diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index 6140e79..7db0302 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -376,6 +376,8 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long stack_start, */ fpsimd_flush_task_state(p); + ptrauth_thread_init_kernel(p); + if (likely(!(p->flags & PF_KTHREAD))) { *childregs = *current_pt_regs(); childregs->regs[0] = 0; diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c index d4ed9a1..0890341 100644 --- a/arch/arm64/kernel/smp.c +++ b/arch/arm64/kernel/smp.c @@ -112,6 +112,10 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle) */ secondary_data.task = idle; secondary_data.stack = task_stack_page(idle) + THREAD_SIZE; +#if defined(CONFIG_ARM64_PTR_AUTH) + secondary_data.ptrauth_key.apia.lo = idle->thread.keys_kernel.apia.lo; + secondary_data.ptrauth_key.apia.hi = idle->thread.keys_kernel.apia.hi; +#endif update_cpu_boot_status(CPU_MMU_OFF); __flush_dcache_area(&secondary_data, sizeof(secondary_data)); @@ -138,6 +142,10 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle) secondary_data.task = NULL; secondary_data.stack = NULL; +#if defined(CONFIG_ARM64_PTR_AUTH) + secondary_data.ptrauth_key.apia.lo = 0; + secondary_data.ptrauth_key.apia.hi = 0; +#endif __flush_dcache_area(&secondary_data, sizeof(secondary_data)); status = READ_ONCE(secondary_data.status); if (ret && status) { diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S index 4cf19a2..5a11a89 100644 --- a/arch/arm64/mm/proc.S +++ b/arch/arm64/mm/proc.S @@ -485,6 +485,10 @@ SYM_FUNC_START(__cpu_setup) ubfx x2, x2, #ID_AA64ISAR1_APA_SHIFT, #8 cbz x2, 3f + /* + * The primary cpu keys are reset here and can be + * re-initialised with some proper values later. + */ msr_s SYS_APIAKEYLO_EL1, xzr msr_s SYS_APIAKEYHI_EL1, xzr @@ -497,6 +501,14 @@ alternative_if_not ARM64_HAS_ADDRESS_AUTH b 3f alternative_else_nop_endif + /* Install ptrauth key for secondary cpus */ + adr_l x2, secondary_data + ldr x3, [x2, #CPU_BOOT_TASK] // get secondary_data.task + cbz x3, 2f // check for slow booting cpus + ldp x3, x4, [x2, #CPU_BOOT_PTRAUTH_KEY] + msr_s SYS_APIAKEYLO_EL1, x3 + msr_s SYS_APIAKEYHI_EL1, x4 + 2: /* Enable ptrauth instructions */ ldr x2, =SCTLR_ELx_ENIA | SCTLR_ELx_ENIB | \ SCTLR_ELx_ENDA | SCTLR_ELx_ENDB -- 2.7.4