From patchwork Tue Jul 28 13:10:49 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Madhavan T. Venkataraman" X-Patchwork-Id: 11689133 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 2E3CF13B6 for ; Tue, 28 Jul 2020 13:11:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 08538206D4 for ; Tue, 28 Jul 2020 13:11:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="Zelt39lG" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730013AbgG1NLH (ORCPT ); Tue, 28 Jul 2020 09:11:07 -0400 Received: from linux.microsoft.com ([13.77.154.182]:37780 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729992AbgG1NLD (ORCPT ); Tue, 28 Jul 2020 09:11:03 -0400 Received: from localhost.localdomain (unknown [47.187.206.220]) by linux.microsoft.com (Postfix) with ESMTPSA id 35EF720B490C; Tue, 28 Jul 2020 06:11:02 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 35EF720B490C DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1595941862; bh=8Vxha6xG5iZEw3wvrMCm+5RmpGmvMZada0wtXeD9y+A=; h=From:To:Subject:Date:In-Reply-To:References:From; b=Zelt39lGKsDTqpf+B5KIBob2G2aSNP3d2dICWZ2pAI4O7+mYJ1o3rMJZM+ta1LBFe My84y/3nj6OMcfg6VvYOSJHbwcHzyazxuBzfljnbMntH9BAE8jiqNR+HBZMvy6tC87 CEAIa/3w8Z+GlTF6lqrgxbBMstTNru2mXoJYPUTU= From: madvenka@linux.microsoft.com To: kernel-hardening@lists.openwall.com, linux-api@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, oleg@redhat.com, x86@kernel.org, madvenka@linux.microsoft.com Subject: [PATCH v1 3/4] [RFC] arm64/trampfd: Provide support for the trampoline file descriptor Date: Tue, 28 Jul 2020 08:10:49 -0500 Message-Id: <20200728131050.24443-4-madvenka@linux.microsoft.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200728131050.24443-1-madvenka@linux.microsoft.com> References: <20200728131050.24443-1-madvenka@linux.microsoft.com> Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: From: "Madhavan T. Venkataraman" Implement 64-bit ARM support for the trampoline file descriptor. - Define architecture specific register names - Handle the trampoline invocation page fault - Setup the user register context on trampoline invocation - Setup the user stack context on trampoline invocation Signed-off-by: Madhavan T. Venkataraman --- arch/arm64/include/asm/ptrace.h | 9 + arch/arm64/include/asm/unistd.h | 2 +- arch/arm64/include/asm/unistd32.h | 2 + arch/arm64/include/uapi/asm/ptrace.h | 57 ++++++ arch/arm64/kernel/Makefile | 2 + arch/arm64/kernel/trampfd.c | 278 +++++++++++++++++++++++++++ arch/arm64/mm/fault.c | 15 +- 7 files changed, 361 insertions(+), 4 deletions(-) create mode 100644 arch/arm64/kernel/trampfd.c diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h index 953b6a1ce549..dad6cdbd59c6 100644 --- a/arch/arm64/include/asm/ptrace.h +++ b/arch/arm64/include/asm/ptrace.h @@ -232,6 +232,15 @@ static inline unsigned long user_stack_pointer(struct pt_regs *regs) return regs->sp; } +static inline void user_stack_pointer_set(struct pt_regs *regs, + unsigned long val) +{ + if (compat_user_mode(regs)) + regs->compat_sp = val; + else + regs->sp = val; +} + extern int regs_query_register_offset(const char *name); extern unsigned long regs_get_kernel_stack_nth(struct pt_regs *regs, unsigned int n); diff --git a/arch/arm64/include/asm/unistd.h b/arch/arm64/include/asm/unistd.h index 3b859596840d..b3b2019f8d16 100644 --- a/arch/arm64/include/asm/unistd.h +++ b/arch/arm64/include/asm/unistd.h @@ -38,7 +38,7 @@ #define __ARM_NR_compat_set_tls (__ARM_NR_COMPAT_BASE + 5) #define __ARM_NR_COMPAT_END (__ARM_NR_COMPAT_BASE + 0x800) -#define __NR_compat_syscalls 440 +#define __NR_compat_syscalls 441 #endif #define __ARCH_WANT_SYS_CLONE diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h index 6d95d0c8bf2f..821ddcaf9683 100644 --- a/arch/arm64/include/asm/unistd32.h +++ b/arch/arm64/include/asm/unistd32.h @@ -885,6 +885,8 @@ __SYSCALL(__NR_openat2, sys_openat2) __SYSCALL(__NR_pidfd_getfd, sys_pidfd_getfd) #define __NR_faccessat2 439 __SYSCALL(__NR_faccessat2, sys_faccessat2) +#define __NR_trampfd_create 440 +__SYSCALL(__NR_trampfd_create, sys_trampfd_create) /* * Please add new compat syscalls above this comment and update diff --git a/arch/arm64/include/uapi/asm/ptrace.h b/arch/arm64/include/uapi/asm/ptrace.h index 42cbe34d95ce..f4d1974dd795 100644 --- a/arch/arm64/include/uapi/asm/ptrace.h +++ b/arch/arm64/include/uapi/asm/ptrace.h @@ -88,6 +88,63 @@ struct user_pt_regs { __u64 pstate; }; +/* + * These register names are to be used by 32-bit applications. + */ +enum reg_32_name { + arm_r0, + arm_r1, + arm_r2, + arm_r3, + arm_r4, + arm_r5, + arm_r6, + arm_r7, + arm_r8, + arm_r9, + arm_r10, + arm_ip, + arm_pc, + arm_max, +}; + +/* + * These register names are to be used by 64-bit applications. + */ +enum reg_64_name { + arm64_r0 = arm_max, + arm64_r1, + arm64_r2, + arm64_r3, + arm64_r4, + arm64_r5, + arm64_r6, + arm64_r7, + arm64_r8, + arm64_r9, + arm64_r10, + arm64_r11, + arm64_r12, + arm64_r13, + arm64_r14, + arm64_r15, + arm64_r16, + arm64_r17, + arm64_r18, + arm64_r19, + arm64_r20, + arm64_r21, + arm64_r22, + arm64_r23, + arm64_r24, + arm64_r25, + arm64_r26, + arm64_r27, + arm64_r28, + arm64_pc, + arm64_max, +}; + struct user_fpsimd_state { __uint128_t vregs[32]; __u32 fpsr; diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile index a561cbb91d4d..18d373fb1208 100644 --- a/arch/arm64/kernel/Makefile +++ b/arch/arm64/kernel/Makefile @@ -71,3 +71,5 @@ extra-y += $(head-y) vmlinux.lds ifeq ($(CONFIG_DEBUG_EFI),y) AFLAGS_head.o += -DVMLINUX_PATH="\"$(realpath $(objtree)/vmlinux)\"" endif + +obj-$(CONFIG_TRAMPFD) += trampfd.o diff --git a/arch/arm64/kernel/trampfd.c b/arch/arm64/kernel/trampfd.c new file mode 100644 index 000000000000..d79e749e0c30 --- /dev/null +++ b/arch/arm64/kernel/trampfd.c @@ -0,0 +1,278 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Trampoline File Descriptor - ARM64 support. + * + * Author: Madhavan T. Venkataraman (madvenka@linux.microsoft.com) + * + * Copyright (c) 2020, Microsoft Corporation. + */ + +#include +#include +#include + +/* ---------------------------- Register Context ---------------------------- */ + +static inline bool is_compat(void) +{ + return is_compat_thread(task_thread_info(current)); +} + +static void set_reg_32(struct pt_regs *pt_regs, u32 name, u64 value) +{ + switch (name) { + case arm_r0: + case arm_r1: + case arm_r2: + case arm_r3: + case arm_r4: + case arm_r5: + case arm_r6: + case arm_r7: + case arm_r8: + case arm_r9: + case arm_r10: + pt_regs->regs[name] = (__u64)value; + break; + case arm_ip: + pt_regs->regs[arm64_r16 - arm_max] = (__u64)value; + break; + case arm_pc: + pt_regs->pc = (__u64)value; + break; + default: + WARN(1, "%s: Illegal register name %d\n", __func__, name); + break; + } +} + +static void set_reg_64(struct pt_regs *pt_regs, u32 name, u64 value) +{ + switch (name) { + case arm64_r0: + case arm64_r1: + case arm64_r2: + case arm64_r3: + case arm64_r4: + case arm64_r5: + case arm64_r6: + case arm64_r7: + case arm64_r8: + case arm64_r9: + case arm64_r10: + case arm64_r11: + case arm64_r12: + case arm64_r13: + case arm64_r14: + case arm64_r15: + case arm64_r16: + case arm64_r17: + case arm64_r18: + case arm64_r19: + case arm64_r20: + case arm64_r21: + case arm64_r22: + case arm64_r23: + case arm64_r24: + case arm64_r25: + case arm64_r26: + case arm64_r27: + case arm64_r28: + pt_regs->regs[name - arm_max] = (__u64)value; + break; + case arm64_pc: + pt_regs->pc = (__u64)value; + break; + default: + WARN(1, "%s: Illegal register name %d\n", __func__, name); + break; + } +} + +static void set_regs(struct pt_regs *pt_regs, struct trampfd_regs *tregs) +{ + struct trampfd_reg *reg = tregs->regs; + struct trampfd_reg *reg_end = reg + tregs->nregs; + bool compat = is_compat(); + + for (; reg < reg_end; reg++) { + if (compat) + set_reg_32(pt_regs, reg->name, reg->value); + else + set_reg_64(pt_regs, reg->name, reg->value); + } +} + +/* + * Check if the register names are valid. Check if the user PC has been set. + */ +bool trampfd_valid_regs(struct trampfd_regs *tregs) +{ + struct trampfd_reg *reg = tregs->regs; + struct trampfd_reg *reg_end = reg + tregs->nregs; + int min, max, pc_name; + bool pc_set = false; + + if (is_compat()) { + min = 0; + pc_name = arm_pc; + max = arm_max; + } else { + min = arm_max; + pc_name = arm64_pc; + max = arm64_max; + } + + for (; reg < reg_end; reg++) { + if (reg->name < min || reg->name >= max || reg->reserved) + return false; + if (reg->name == pc_name && reg->value) + pc_set = true; + } + return pc_set; +} +EXPORT_SYMBOL_GPL(trampfd_valid_regs); + +/* + * Check if the PC specified in a register context is allowed. + */ +bool trampfd_allowed_pc(struct trampfd *trampfd, struct trampfd_regs *tregs) +{ + struct trampfd_reg *reg = tregs->regs; + struct trampfd_reg *reg_end = reg + tregs->nregs; + struct trampfd_values *allowed_pcs = trampfd->allowed_pcs; + u64 *allowed_values, pc_value = 0; + u32 nvalues, pc_name; + int i; + + if (!allowed_pcs) + return true; + + pc_name = is_compat() ? arm_pc : arm64_pc; + + /* + * Find the PC register and its value. If the PC register has been + * specified multiple times, only the last one counts. + */ + for (; reg < reg_end; reg++) { + if (reg->name == pc_name) + pc_value = reg->value; + } + + allowed_values = allowed_pcs->values; + nvalues = allowed_pcs->nvalues; + + for (i = 0; i < nvalues; i++) { + if (pc_value == allowed_values[i]) + return true; + } + return false; +} +EXPORT_SYMBOL_GPL(trampfd_allowed_pc); + +/* ---------------------------- Stack Context ---------------------------- */ + +static int push_data(struct pt_regs *pt_regs, struct trampfd_stack *tstack) +{ + unsigned long sp; + + sp = user_stack_pointer(pt_regs) - tstack->size - tstack->offset; + if (tstack->flags & TRAMPFD_SET_SP) + sp = round_down(sp, 16); + + if (!access_ok((void *)sp, user_stack_pointer(pt_regs) - sp)) + return -EFAULT; + + if (copy_to_user(USERPTR(sp), tstack->data, tstack->size)) + return -EFAULT; + + if (tstack->flags & TRAMPFD_SET_SP) + user_stack_pointer_set(pt_regs, sp); + + return 0; +} + +/* ---------------------------- Fault Handlers ---------------------------- */ + +static int trampfd_user_fault(struct trampfd *trampfd, + struct vm_area_struct *vma, + struct pt_regs *pt_regs) +{ + char buf[TRAMPFD_MAX_STACK_SIZE]; + struct trampfd_regs *tregs; + struct trampfd_stack *tstack = NULL; + unsigned long addr; + size_t size; + int rc = 0; + + mutex_lock(&trampfd->lock); + + /* + * Execution of the trampoline must start at the offset specfied by + * the kernel. + */ + addr = vma->vm_start + trampfd->map.ioffset; + if (addr != pt_regs->pc) { + rc = -EINVAL; + goto unlock; + } + + /* + * At a minimum, the user PC register must be specified for a + * user trampoline. + */ + tregs = trampfd->regs; + if (!tregs) { + rc = -EINVAL; + goto unlock; + } + + /* + * Set the register context for the trampoline. + */ + set_regs(pt_regs, tregs); + + if (trampfd->stack) { + /* + * Copy the stack context into a local buffer and push stack + * data after dropping the lock. + */ + size = sizeof(*trampfd->stack) + trampfd->stack->size; + tstack = (struct trampfd_stack *) buf; + memcpy(tstack, trampfd->stack, size); + } +unlock: + mutex_unlock(&trampfd->lock); + + if (!rc && tstack) { + mmap_read_unlock(vma->vm_mm); + rc = push_data(pt_regs, tstack); + mmap_read_lock(vma->vm_mm); + } + return rc; +} + +/* + * Handle it if it is a trampoline fault. + */ +bool trampfd_fault(struct vm_area_struct *vma, struct pt_regs *pt_regs) +{ + struct trampfd *trampfd; + + if (!is_trampfd_vma(vma)) + return false; + trampfd = vma->vm_private_data; + + if (trampfd->type == TRAMPFD_USER) + return !trampfd_user_fault(trampfd, vma, pt_regs); + return false; +} +EXPORT_SYMBOL_GPL(trampfd_fault); + +/* ---------------------------- Miscellaneous ---------------------------- */ + +int trampfd_check_arch(struct trampfd *trampfd) +{ + return 0; +} +EXPORT_SYMBOL_GPL(trampfd_check_arch); diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index 8afb238ff335..6e5e3193919a 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -23,6 +23,7 @@ #include #include #include +#include #include #include @@ -404,7 +405,8 @@ static void do_bad_area(unsigned long addr, unsigned int esr, struct pt_regs *re #define VM_FAULT_BADACCESS 0x020000 static vm_fault_t __do_page_fault(struct mm_struct *mm, unsigned long addr, - unsigned int mm_flags, unsigned long vm_flags) + unsigned int mm_flags, unsigned long vm_flags, + struct pt_regs *regs) { struct vm_area_struct *vma = find_vma(mm, addr); @@ -426,8 +428,15 @@ static vm_fault_t __do_page_fault(struct mm_struct *mm, unsigned long addr, * Check that the permissions on the VMA allow for the fault which * occurred. */ - if (!(vma->vm_flags & vm_flags)) + if (!(vma->vm_flags & vm_flags)) { + /* + * If it is an execute fault, it could be a trampoline + * invocation. + */ + if ((vm_flags & VM_EXEC) && trampfd_fault(vma, regs)) + return 0; return VM_FAULT_BADACCESS; + } return handle_mm_fault(vma, addr & PAGE_MASK, mm_flags); } @@ -516,7 +525,7 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, #endif } - fault = __do_page_fault(mm, addr, mm_flags, vm_flags); + fault = __do_page_fault(mm, addr, mm_flags, vm_flags, regs); major |= fault & VM_FAULT_MAJOR; /* Quick path to respond to signals */