[06/10] x86/cet: Add arch_prctl functions for shadow stack

Message ID	20180607143807.3611-7-yu-cheng.yu@intel.com (mailing list archive)
State	New, archived
Headers	show Return-Path: <owner-linux-mm@kvack.org> Received-SPF: pass (google.com: domain of yu-cheng.yu@intel.com designates 192.55.52.43 as permitted sender) client-ip=192.55.52.43; From: Yu-cheng Yu <yu-cheng.yu@intel.com> To: linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, "H.J. Lu" <hjl.tools@gmail.com>, Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com>, "Ravi V. Shankar" <ravi.v.shankar@intel.com>, Dave Hansen <dave.hansen@linux.intel.com>, Andy Lutomirski <luto@amacapital.net>, Jonathan Corbet <corbet@lwn.net>, Oleg Nesterov <oleg@redhat.com>, Arnd Bergmann <arnd@arndb.de>, Mike Kravetz <mike.kravetz@oracle.com> Cc: Yu-cheng Yu <yu-cheng.yu@intel.com> Subject: [PATCH 06/10] x86/cet: Add arch_prctl functions for shadow stack Date: Thu, 7 Jun 2018 07:38:03 -0700 Message-Id: <20180607143807.3611-7-yu-cheng.yu@intel.com> In-Reply-To: <20180607143807.3611-1-yu-cheng.yu@intel.com> References: <20180607143807.3611-1-yu-cheng.yu@intel.com> Sender: owner-linux-mm@kvack.org Precedence: bulk

diff --git a/arch/x86/include/asm/cet.h b/arch/x86/include/asm/cet.h index c8fd87e13859..a2a53fe4d5e6 100644 --- a/arch/x86/include/asm/cet.h +++ b/arch/x86/include/asm/cet.h @@ -12,24 +12,31 @@ struct task_struct; struct cet_stat { unsigned long shstk_base; unsigned long shstk_size; + unsigned long exec_shstk_size; unsigned int shstk_enabled:1; + unsigned int locked:1; + unsigned int exec_shstk:2; }; #ifdef CONFIG_X86_INTEL_CET +int prctl_cet(int option, unsigned long arg2); unsigned long cet_get_shstk_ptr(void); int cet_push_shstk(int ia32, unsigned long ssp, unsigned long val); int cet_setup_shstk(void); int cet_setup_thread_shstk(struct task_struct *p); +int cet_alloc_shstk(unsigned long *arg); void cet_disable_shstk(void); void cet_disable_free_shstk(struct task_struct *p); int cet_restore_signal(unsigned long ssp); int cet_setup_signal(int ia32, unsigned long addr); #else +static inline int prctl_cet(int option, unsigned long arg2) { return 0; } static inline unsigned long cet_get_shstk_ptr(void) { return 0; } static inline int cet_push_shstk(int ia32, unsigned long ssp, unsigned long val) { return 0; } static inline int cet_setup_shstk(void) { return 0; } static inline int cet_setup_thread_shstk(struct task_struct *p) { return 0; } +static inline int cet_alloc_shstk(unsigned long *arg) { return -EINVAL; } static inline void cet_disable_shstk(void) {} static inline void cet_disable_free_shstk(struct task_struct *p) {} static inline int cet_restore_signal(unsigned long ssp) { return 0; } diff --git a/arch/x86/include/uapi/asm/prctl.h b/arch/x86/include/uapi/asm/prctl.h index 5a6aac9fa41f..f9965403b655 100644 --- a/arch/x86/include/uapi/asm/prctl.h +++ b/arch/x86/include/uapi/asm/prctl.h @@ -14,4 +14,19 @@ #define ARCH_MAP_VDSO_32 0x2002 #define ARCH_MAP_VDSO_64 0x2003 +#define ARCH_CET_STATUS 0x3001 +#define ARCH_CET_DISABLE 0x3002 +#define ARCH_CET_LOCK 0x3003 +#define ARCH_CET_EXEC 0x3004 +#define ARCH_CET_ALLOC_SHSTK 0x3005 +#define ARCH_CET_PUSH_SHSTK 0x3006 + +/* + * Settings for ARCH_CET_EXEC + */ +#define CET_EXEC_ELF_PROPERTY 0 +#define CET_EXEC_ALWAYS_OFF 1 +#define CET_EXEC_ALWAYS_ON 2 +#define CET_EXEC_MAX CET_EXEC_ALWAYS_ON + #endif /* _ASM_X86_PRCTL_H */ diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile index cbf983f44b61..80464f925a6a 100644 --- a/arch/x86/kernel/Makefile +++ b/arch/x86/kernel/Makefile @@ -138,7 +138,7 @@ obj-$(CONFIG_UNWINDER_ORC) += unwind_orc.o obj-$(CONFIG_UNWINDER_FRAME_POINTER) += unwind_frame.o obj-$(CONFIG_UNWINDER_GUESS) += unwind_guess.o -obj-$(CONFIG_X86_INTEL_CET) += cet.o +obj-$(CONFIG_X86_INTEL_CET) += cet.o cet_prctl.o obj-$(CONFIG_ARCH_HAS_PROGRAM_PROPERTIES) += elf.o diff --git a/arch/x86/kernel/cet.c b/arch/x86/kernel/cet.c index 156f5d88ffd5..1b7089dcf1ea 100644 --- a/arch/x86/kernel/cet.c +++ b/arch/x86/kernel/cet.c @@ -83,6 +83,19 @@ static unsigned long shstk_mmap(unsigned long addr, unsigned long len) return addr; } +int cet_alloc_shstk(unsigned long *arg) +{ + unsigned long size = *arg; + unsigned long addr; + + addr = shstk_mmap(0, size); + if (addr >= TASK_SIZE) + return -ENOMEM; + + *arg = addr; + return 0; +} + int cet_setup_shstk(void) { unsigned long addr, size; @@ -90,7 +103,10 @@ int cet_setup_shstk(void) if (!cpu_feature_enabled(X86_FEATURE_SHSTK)) return -EOPNOTSUPP; - size = SHSTK_SIZE; + size = current->thread.cet.exec_shstk_size; + if ((size > TASK_SIZE) || (size == 0)) + size = SHSTK_SIZE; + addr = shstk_mmap(0, size); if (addr >= TASK_SIZE) diff --git a/arch/x86/kernel/cet_prctl.c b/arch/x86/kernel/cet_prctl.c new file mode 100644 index 000000000000..326996e2ea80 --- /dev/null +++ b/arch/x86/kernel/cet_prctl.c @@ -0,0 +1,203 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +#include <linux/errno.h> +#include <linux/uaccess.h> +#include <linux/prctl.h> +#include <linux/compat.h> +#include <asm/processor.h> +#include <asm/prctl.h> +#include <asm/elf.h> +#include <asm/elf_property.h> +#include <asm/cet.h> + +/* + * Handler of prctl for CET: + * + * ARCH_CET_STATUS: return the current status + * ARCH_CET_DISABLE: disable features + * ARCH_CET_LOCK: lock out cet features until exec() + * ARCH_CET_EXEC: set default features for exec() + * ARCH_CET_ALLOC_SHSTK: allocate shadow stack + * ARCH_CET_PUSH_SHSTK: put a return address on shadow stack + */ + +static int handle_get_status(unsigned long arg2) +{ + unsigned int features = 0, cet_exec = 0; + unsigned long shstk_size = 0; + + if (current->thread.cet.shstk_enabled) + features |= GNU_PROPERTY_X86_FEATURE_1_SHSTK; + if (current->thread.cet.exec_shstk == CET_EXEC_ALWAYS_ON) + cet_exec |= GNU_PROPERTY_X86_FEATURE_1_SHSTK; + shstk_size = current->thread.cet.exec_shstk_size; + + if (in_compat_syscall()) { + unsigned int buf[3]; + + buf[0] = features; + buf[1] = cet_exec; + buf[2] = (unsigned int)shstk_size; + return copy_to_user((unsigned int __user *)arg2, buf, + sizeof(buf)); + } else { + unsigned long buf[3]; + + buf[0] = (unsigned long)features; + buf[1] = (unsigned long)cet_exec; + buf[2] = shstk_size; + return copy_to_user((unsigned long __user *)arg2, buf, + sizeof(buf)); + } +} + +static int handle_set_exec(unsigned long arg2) +{ + unsigned int features = 0, cet_exec = 0; + unsigned long shstk_size = 0; + int err = 0; + + if (in_compat_syscall()) { + unsigned int buf[3]; + + err = copy_from_user(buf, (unsigned int __user *)arg2, + sizeof(buf)); + if (!err) { + features = buf[0]; + cet_exec = buf[1]; + shstk_size = (unsigned long)buf[2]; + } + } else { + unsigned long buf[3]; + + err = copy_from_user(buf, (unsigned long __user *)arg2, + sizeof(buf)); + if (!err) { + features = (unsigned int)buf[0]; + cet_exec = (unsigned int)buf[1]; + shstk_size = buf[2]; + } + } + + if (err) + return -EFAULT; + if (cet_exec > CET_EXEC_MAX) + return -EINVAL; + if (shstk_size >= TASK_SIZE) + return -EINVAL; + + if (features & GNU_PROPERTY_X86_FEATURE_1_SHSTK) { + if (!cpu_feature_enabled(X86_FEATURE_SHSTK)) + return -EINVAL; + if ((current->thread.cet.exec_shstk == CET_EXEC_ALWAYS_ON) && + (cet_exec != CET_EXEC_ALWAYS_ON)) + return -EPERM; + } + + if (features & GNU_PROPERTY_X86_FEATURE_1_SHSTK) + current->thread.cet.exec_shstk = cet_exec; + + current->thread.cet.exec_shstk_size = shstk_size; + return 0; +} + +static int handle_push_shstk(unsigned long arg2) +{ + unsigned long ssp = 0, ret_addr = 0; + int ia32, err; + + ia32 = in_ia32_syscall(); + + if (ia32) { + unsigned int buf[2]; + + err = copy_from_user(buf, (unsigned int __user *)arg2, + sizeof(buf)); + if (!err) { + ssp = (unsigned long)buf[0]; + ret_addr = (unsigned long)buf[1]; + } + } else { + unsigned long buf[2]; + + err = copy_from_user(buf, (unsigned long __user *)arg2, + sizeof(buf)); + if (!err) { + ssp = buf[0]; + ret_addr = buf[1]; + } + } + if (err) + return -EFAULT; + err = cet_push_shstk(ia32, ssp, ret_addr); + if (err) + return -err; + return 0; +} + +static int handle_alloc_shstk(unsigned long arg2) +{ + int err = 0; + unsigned long shstk_size = 0; + + if (in_ia32_syscall()) { + unsigned int size; + + err = get_user(size, (unsigned int __user *)arg2); + if (!err) + shstk_size = size; + } else { + err = get_user(shstk_size, (unsigned long __user *)arg2); + } + + if (err) + return -EFAULT; + + err = cet_alloc_shstk(&shstk_size); + if (err) + return -err; + + if (in_ia32_syscall()) { + if (put_user(shstk_size, (unsigned int __user *)arg2)) + return -EFAULT; + } else { + if (put_user(shstk_size, (unsigned long __user *)arg2)) + return -EFAULT; + } + return 0; +} + +int prctl_cet(int option, unsigned long arg2) +{ + if (!cpu_feature_enabled(X86_FEATURE_SHSTK)) + return -EINVAL; + + switch (option) { + case ARCH_CET_STATUS: + return handle_get_status(arg2); + + case ARCH_CET_DISABLE: + if (current->thread.cet.locked) + return -EPERM; + if (arg2 & GNU_PROPERTY_X86_FEATURE_1_SHSTK) + cet_disable_free_shstk(current); + + return 0; + + case ARCH_CET_LOCK: + current->thread.cet.locked = 1; + return 0; + + case ARCH_CET_EXEC: + return handle_set_exec(arg2); + + case ARCH_CET_ALLOC_SHSTK: + return handle_alloc_shstk(arg2); + + case ARCH_CET_PUSH_SHSTK: + return handle_push_shstk(arg2); + + default: + return -EINVAL; + } +} diff --git a/arch/x86/kernel/elf.c b/arch/x86/kernel/elf.c index 8e2719d8dc86..de08d41971f6 100644 --- a/arch/x86/kernel/elf.c +++ b/arch/x86/kernel/elf.c @@ -8,7 +8,10 @@ #include <asm/cet.h> #include <asm/elf_property.h> +#include <asm/prctl.h> +#include <asm/processor.h> #include <uapi/linux/elf-em.h> +#include <uapi/linux/prctl.h> #include <linux/binfmts.h> #include <linux/elf.h> #include <linux/slab.h> @@ -208,13 +211,26 @@ int arch_setup_features(void *ehdr_p, void *phdr_p, current->thread.cet.shstk_enabled = 0; current->thread.cet.shstk_base = 0; current->thread.cet.shstk_size = 0; + current->thread.cet.locked = 0; if (cpu_feature_enabled(X86_FEATURE_SHSTK)) { - if (shstk) { - err = cet_setup_shstk(); - if (err < 0) - goto out; + int exec = current->thread.cet.exec_shstk; + + if (exec != CET_EXEC_ALWAYS_OFF) { + if (shstk || (exec == CET_EXEC_ALWAYS_ON)) { + err = cet_setup_shstk(); + if (err < 0) + goto out; + } } } + + /* + * Lockout CET features if no interpreter + */ + if (!interp) + current->thread.cet.locked = 1; + + err = 0; out: return err; } diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index ae56caee41f9..54ad1863c6d2 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -794,6 +794,13 @@ long do_arch_prctl_common(struct task_struct *task, int option, return get_cpuid_mode(); case ARCH_SET_CPUID: return set_cpuid_mode(task, cpuid_enabled); + case ARCH_CET_STATUS: + case ARCH_CET_DISABLE: + case ARCH_CET_LOCK: + case ARCH_CET_EXEC: + case ARCH_CET_ALLOC_SHSTK: + case ARCH_CET_PUSH_SHSTK: + return prctl_cet(option, cpuid_enabled); } return -EINVAL;

[06/10] x86/cet: Add arch_prctl functions for shadow stack

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