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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=HxSYBdgam0Oo55tV66MssX9ym6F+6IzxUZWIIcNmGrg=; b=WWbwTzgYGJ0BmSozaJoNst11Ntd5n4963mJIiyygWc2ZoRT/QMkIMR9WUIlwJ6AGhZ NXBZKixr3PmpID54MkSnmT1jQx2Hmy+5l1jg1HB3rlPlgYtJbFeCp5PwvdKPWWmgIhRZ XP9jY4UIb4U59AHXXBRniDrC21SlQNEIxLcg5hDjSWxC2KftERLDGbe0+fZUIUjFrfIC Pu98phH7yvSgMziMLPzjAyoLglwGaX7ytdkWcfEsEsZhkG4vAzqZGX4l0L7EFB1dfZA1 vFiQY50+I6t/SoXzysPlQCKYKwvRPI6Sj9l8+H0hww+4vM9AI3YfeJlFkG4LwOYK6/jl wlTA== X-Gm-Message-State: APjAAAWupi5skGl/fW3zl/9h9OhdrEh5KpXj3rSYJpODeObiwISE/asW LP6Blj6V7hIgVAID6qCEzQkOKBiUK90SjFWeBjI= X-Google-Smtp-Source: APXvYqxNR5Ky752e4R5eO8G3NKpwk/PIoAWuLwRPj4GBI9f/daXjqYVW+U928uYW3/V5py/PVaYozr9rWrjWTEXLiZc= X-Received: by 2002:a05:6214:1874:: with SMTP id eh20mr19345297qvb.122.1582070939036; Tue, 18 Feb 2020 16:08:59 -0800 (PST) Date: Tue, 18 Feb 2020 16:08:15 -0800 In-Reply-To: <20200219000817.195049-1-samitolvanen@google.com> Message-Id: <20200219000817.195049-11-samitolvanen@google.com> Mime-Version: 1.0 References: <20191018161033.261971-1-samitolvanen@google.com> <20200219000817.195049-1-samitolvanen@google.com> X-Mailer: git-send-email 2.25.0.265.gbab2e86ba0-goog Subject: [PATCH v8 10/12] arm64: implement Shadow Call Stack From: Sami Tolvanen To: Will Deacon , Catalin Marinas , Steven Rostedt , Masami Hiramatsu , Ard Biesheuvel , Mark Rutland , james.morse@arm.com X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200218_160901_468957_00FD0DC4 X-CRM114-Status: GOOD ( 18.92 ) X-Spam-Score: -7.7 (-------) X-Spam-Report: SpamAssassin version 3.4.3 on bombadil.infradead.org summary: Content analysis details: (-7.7 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 SPF_PASS SPF: sender matches SPF record 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -7.5 USER_IN_DEF_DKIM_WL From: address is in the default DKIM white-list 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from envelope-from domain -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature -0.0 DKIMWL_WL_MED DKIMwl.org - Medium sender X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kees Cook , Jann Horn , Masahiro Yamada , Marc Zyngier , kernel-hardening@lists.openwall.com, Nick Desaulniers , linux-kernel@vger.kernel.org, Miguel Ojeda , clang-built-linux@googlegroups.com, Sami Tolvanen , Laura Abbott , Dave Martin , linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org This change implements shadow stack switching, initial SCS set-up, and interrupt shadow stacks for arm64. Signed-off-by: Sami Tolvanen Reviewed-by: Kees Cook --- arch/arm64/Kconfig | 5 ++++ arch/arm64/include/asm/scs.h | 37 +++++++++++++++++++++++++ arch/arm64/include/asm/thread_info.h | 3 +++ arch/arm64/kernel/Makefile | 1 + arch/arm64/kernel/asm-offsets.c | 3 +++ arch/arm64/kernel/entry.S | 32 ++++++++++++++++++++-- arch/arm64/kernel/head.S | 9 +++++++ arch/arm64/kernel/irq.c | 2 ++ arch/arm64/kernel/process.c | 2 ++ arch/arm64/kernel/scs.c | 40 ++++++++++++++++++++++++++++ arch/arm64/kernel/smp.c | 4 +++ 11 files changed, 136 insertions(+), 2 deletions(-) create mode 100644 arch/arm64/include/asm/scs.h create mode 100644 arch/arm64/kernel/scs.c diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 0b30e884e088..eae76686be77 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -65,6 +65,7 @@ config ARM64 select ARCH_USE_QUEUED_RWLOCKS select ARCH_USE_QUEUED_SPINLOCKS select ARCH_SUPPORTS_MEMORY_FAILURE + select ARCH_SUPPORTS_SHADOW_CALL_STACK if CC_HAVE_SHADOW_CALL_STACK select ARCH_SUPPORTS_ATOMIC_RMW select ARCH_SUPPORTS_INT128 if CC_HAS_INT128 && (GCC_VERSION >= 50000 || CC_IS_CLANG) select ARCH_SUPPORTS_NUMA_BALANCING @@ -1022,6 +1023,10 @@ config ARCH_HAS_CACHE_LINE_SIZE config ARCH_ENABLE_SPLIT_PMD_PTLOCK def_bool y if PGTABLE_LEVELS > 2 +# Supported by clang >= 7.0 +config CC_HAVE_SHADOW_CALL_STACK + def_bool $(cc-option, -fsanitize=shadow-call-stack -ffixed-x18) + config SECCOMP bool "Enable seccomp to safely compute untrusted bytecode" ---help--- diff --git a/arch/arm64/include/asm/scs.h b/arch/arm64/include/asm/scs.h new file mode 100644 index 000000000000..c50d2b0c6c5f --- /dev/null +++ b/arch/arm64/include/asm/scs.h @@ -0,0 +1,37 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_SCS_H +#define _ASM_SCS_H + +#ifndef __ASSEMBLY__ + +#include + +#ifdef CONFIG_SHADOW_CALL_STACK + +extern void scs_init_irq(void); + +static __always_inline void scs_save(struct task_struct *tsk) +{ + void *s; + + asm volatile("mov %0, x18" : "=r" (s)); + task_set_scs(tsk, s); +} + +static inline void scs_overflow_check(struct task_struct *tsk) +{ + if (unlikely(scs_corrupted(tsk))) + panic("corrupted shadow stack detected inside scheduler\n"); +} + +#else /* CONFIG_SHADOW_CALL_STACK */ + +static inline void scs_init_irq(void) {} +static inline void scs_save(struct task_struct *tsk) {} +static inline void scs_overflow_check(struct task_struct *tsk) {} + +#endif /* CONFIG_SHADOW_CALL_STACK */ + +#endif /* __ASSEMBLY __ */ + +#endif /* _ASM_SCS_H */ diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h index f0cec4160136..8c73764b9ed2 100644 --- a/arch/arm64/include/asm/thread_info.h +++ b/arch/arm64/include/asm/thread_info.h @@ -41,6 +41,9 @@ struct thread_info { #endif } preempt; }; +#ifdef CONFIG_SHADOW_CALL_STACK + void *shadow_call_stack; +#endif }; #define thread_saved_pc(tsk) \ diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile index fc6488660f64..08fafc4da2cf 100644 --- a/arch/arm64/kernel/Makefile +++ b/arch/arm64/kernel/Makefile @@ -63,6 +63,7 @@ obj-$(CONFIG_CRASH_CORE) += crash_core.o obj-$(CONFIG_ARM_SDE_INTERFACE) += sdei.o obj-$(CONFIG_ARM64_SSBD) += ssbd.o obj-$(CONFIG_ARM64_PTR_AUTH) += pointer_auth.o +obj-$(CONFIG_SHADOW_CALL_STACK) += scs.o obj-y += vdso/ probes/ obj-$(CONFIG_COMPAT_VDSO) += vdso32/ diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c index a5bdce8af65b..d485dc5cd196 100644 --- a/arch/arm64/kernel/asm-offsets.c +++ b/arch/arm64/kernel/asm-offsets.c @@ -33,6 +33,9 @@ int main(void) DEFINE(TSK_TI_ADDR_LIMIT, offsetof(struct task_struct, thread_info.addr_limit)); #ifdef CONFIG_ARM64_SW_TTBR0_PAN DEFINE(TSK_TI_TTBR0, offsetof(struct task_struct, thread_info.ttbr0)); +#endif +#ifdef CONFIG_SHADOW_CALL_STACK + DEFINE(TSK_TI_SCS, offsetof(struct task_struct, thread_info.shadow_call_stack)); #endif DEFINE(TSK_STACK, offsetof(struct task_struct, stack)); #ifdef CONFIG_STACKPROTECTOR diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 9461d812ae27..4b18c3bbdea5 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -177,6 +177,10 @@ alternative_cb_end apply_ssbd 1, x22, x23 +#ifdef CONFIG_SHADOW_CALL_STACK + ldr x18, [tsk, #TSK_TI_SCS] // Restore shadow call stack + str xzr, [tsk, #TSK_TI_SCS] // Limit visibility of saved SCS +#endif .else add x21, sp, #S_FRAME_SIZE get_current_task tsk @@ -278,6 +282,12 @@ alternative_else_nop_endif ct_user_enter .endif +#ifdef CONFIG_SHADOW_CALL_STACK + .if \el == 0 + str x18, [tsk, #TSK_TI_SCS] // Save shadow call stack + .endif +#endif + #ifdef CONFIG_ARM64_SW_TTBR0_PAN /* * Restore access to TTBR0_EL1. If returning to EL0, no need for SPSR @@ -383,6 +393,9 @@ alternative_insn eret, nop, ARM64_UNMAP_KERNEL_AT_EL0 .macro irq_stack_entry mov x19, sp // preserve the original sp +#ifdef CONFIG_SHADOW_CALL_STACK + mov x24, x18 // preserve the original shadow stack +#endif /* * Compare sp with the base of the task stack. @@ -400,15 +413,25 @@ alternative_insn eret, nop, ARM64_UNMAP_KERNEL_AT_EL0 /* switch to the irq stack */ mov sp, x26 + +#ifdef CONFIG_SHADOW_CALL_STACK + /* also switch to the irq shadow stack */ + ldr_this_cpu x18, irq_shadow_call_stack_ptr, x26 +#endif + 9998: .endm /* - * x19 should be preserved between irq_stack_entry and - * irq_stack_exit. + * The callee-saved regs (x19-x29) should be preserved between + * irq_stack_entry and irq_stack_exit, but note that kernel_entry + * uses x20-x23 to store data for later use. */ .macro irq_stack_exit mov sp, x19 +#ifdef CONFIG_SHADOW_CALL_STACK + mov x18, x24 +#endif .endm /* GPRs used by entry code */ @@ -895,6 +918,11 @@ ENTRY(cpu_switch_to) ldr lr, [x8] mov sp, x9 msr sp_el0, x1 +#ifdef CONFIG_SHADOW_CALL_STACK + str x18, [x0, #TSK_TI_SCS] + ldr x18, [x1, #TSK_TI_SCS] + str xzr, [x1, #TSK_TI_SCS] // limit visibility of saved SCS +#endif ret ENDPROC(cpu_switch_to) NOKPROBE(cpu_switch_to) diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 989b1944cb71..ca561de903d4 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -27,6 +27,7 @@ #include #include #include +#include #include #include #include @@ -424,6 +425,10 @@ __primary_switched: stp xzr, x30, [sp, #-16]! mov x29, sp +#ifdef CONFIG_SHADOW_CALL_STACK + adr_l x18, init_shadow_call_stack // Set shadow call stack +#endif + str_l x21, __fdt_pointer, x5 // Save FDT pointer ldr_l x4, kimage_vaddr // Save the offset between @@ -731,6 +736,10 @@ __secondary_switched: ldr x2, [x0, #CPU_BOOT_TASK] cbz x2, __secondary_too_slow msr sp_el0, x2 +#ifdef CONFIG_SHADOW_CALL_STACK + ldr x18, [x2, #TSK_TI_SCS] // set shadow call stack + str xzr, [x2, #TSK_TI_SCS] // limit visibility of saved SCS +#endif mov x29, #0 mov x30, #0 b secondary_start_kernel diff --git a/arch/arm64/kernel/irq.c b/arch/arm64/kernel/irq.c index 04a327ccf84d..fe0ca522ff60 100644 --- a/arch/arm64/kernel/irq.c +++ b/arch/arm64/kernel/irq.c @@ -21,6 +21,7 @@ #include #include #include +#include unsigned long irq_err_count; @@ -63,6 +64,7 @@ static void init_irq_stacks(void) void __init init_IRQ(void) { init_irq_stacks(); + scs_init_irq(); irqchip_init(); if (!handle_arch_irq) panic("No interrupt controller found."); diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index 00626057a384..9151616c354c 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -52,6 +52,7 @@ #include #include #include +#include #include #if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_STACKPROTECTOR_PER_TASK) @@ -514,6 +515,7 @@ __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev, uao_thread_switch(next); ptrauth_thread_switch(next); ssbs_thread_switch(next); + scs_overflow_check(next); /* * Complete any pending TLB or cache maintenance on this CPU in case diff --git a/arch/arm64/kernel/scs.c b/arch/arm64/kernel/scs.c new file mode 100644 index 000000000000..eaadf5430baa --- /dev/null +++ b/arch/arm64/kernel/scs.c @@ -0,0 +1,40 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Shadow Call Stack support. + * + * Copyright (C) 2019 Google LLC + */ + +#include +#include +#include +#include + +DEFINE_PER_CPU(unsigned long *, irq_shadow_call_stack_ptr); + +#ifndef CONFIG_SHADOW_CALL_STACK_VMAP +DEFINE_PER_CPU(unsigned long [SCS_SIZE/sizeof(long)], irq_shadow_call_stack) + __aligned(SCS_SIZE); +#endif + +void scs_init_irq(void) +{ + int cpu; + + for_each_possible_cpu(cpu) { +#ifdef CONFIG_SHADOW_CALL_STACK_VMAP + unsigned long *p; + + p = __vmalloc_node_range(PAGE_SIZE, SCS_SIZE, + VMALLOC_START, VMALLOC_END, + GFP_SCS, PAGE_KERNEL, + 0, cpu_to_node(cpu), + __builtin_return_address(0)); + + per_cpu(irq_shadow_call_stack_ptr, cpu) = p; +#else + per_cpu(irq_shadow_call_stack_ptr, cpu) = + per_cpu(irq_shadow_call_stack, cpu); +#endif /* CONFIG_SHADOW_CALL_STACK_VMAP */ + } +} diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c index d4ed9a19d8fe..f2cb344f998c 100644 --- a/arch/arm64/kernel/smp.c +++ b/arch/arm64/kernel/smp.c @@ -46,6 +46,7 @@ #include #include #include +#include #include #include #include @@ -358,6 +359,9 @@ void cpu_die(void) { unsigned int cpu = smp_processor_id(); + /* Save the shadow stack pointer before exiting the idle task */ + scs_save(current); + idle_task_exit(); local_daif_mask();