From: Kees Cook <keescook@chromium.org>
To: Yu-cheng Yu <yu-cheng.yu@intel.com>
Cc: x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
linux-mm@kvack.org, linux-arch@vger.kernel.org,
linux-api@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
Andy Lutomirski <luto@kernel.org>,
Balbir Singh <bsingharora@gmail.com>,
Borislav Petkov <bp@alien8.de>,
Cyrill Gorcunov <gorcunov@gmail.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Eugene Syromiatnikov <esyr@redhat.com>,
Florian Weimer <fweimer@redhat.com>,
"H.J. Lu" <hjl.tools@gmail.com>, Jann Horn <jannh@google.com>,
Jonathan Corbet <corbet@lwn.net>,
Mike Kravetz <mike.kravetz@oracle.com>,
Nadav Amit <nadav.amit@gmail.com>,
Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
Peter Zijlstra <peterz@infradead.org>,
Randy Dunlap <rdunlap@infradead.org>,
"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com>,
Dave Martin <Dave.Martin@arm.com>,
Weijiang Yang <weijiang.yang@intel.com>,
Pengfei Xu <pengfei.xu@intel.com>
Subject: Re: [PATCH v19 24/25] x86/cet/shstk: Add arch_prctl functions for shadow stack
Date: Thu, 4 Feb 2021 12:35:39 -0800 [thread overview]
Message-ID: <202102041235.BA6C4982F@keescook> (raw)
In-Reply-To: <20210203225547.32221-25-yu-cheng.yu@intel.com>
On Wed, Feb 03, 2021 at 02:55:46PM -0800, Yu-cheng Yu wrote:
> arch_prctl(ARCH_X86_CET_STATUS, u64 *args)
> Get CET feature status.
>
> The parameter 'args' is a pointer to a user buffer. The kernel returns
> the following information:
>
> *args = shadow stack/IBT status
> *(args + 1) = shadow stack base address
> *(args + 2) = shadow stack size
What happens if this needs to grow in the future? Should the first u64
contain the array size?
Otherwise, looks sensible.
-Kees
>
> 32-bit binaries use the same interface, but only lower 32-bits of each
> item.
>
> arch_prctl(ARCH_X86_CET_DISABLE, unsigned int features)
> Disable CET features specified in 'features'. Return -EPERM if CET is
> locked.
>
> arch_prctl(ARCH_X86_CET_LOCK)
> Lock in CET features.
>
> Also change do_arch_prctl_common()'s parameter 'cpuid_enabled' to
> 'arg2', as it is now also passed to prctl_cet().
>
> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
> ---
> arch/x86/include/asm/cet.h | 3 ++
> arch/x86/include/uapi/asm/prctl.h | 4 +++
> arch/x86/kernel/Makefile | 2 +-
> arch/x86/kernel/cet_prctl.c | 60 +++++++++++++++++++++++++++++++
> arch/x86/kernel/process.c | 6 ++--
> 5 files changed, 71 insertions(+), 4 deletions(-)
> create mode 100644 arch/x86/kernel/cet_prctl.c
>
> diff --git a/arch/x86/include/asm/cet.h b/arch/x86/include/asm/cet.h
> index ec4b5e62d0ce..16870e5bc8eb 100644
> --- a/arch/x86/include/asm/cet.h
> +++ b/arch/x86/include/asm/cet.h
> @@ -14,9 +14,11 @@ struct sc_ext;
> struct cet_status {
> unsigned long shstk_base;
> unsigned long shstk_size;
> + unsigned int locked:1;
> };
>
> #ifdef CONFIG_X86_CET
> +int prctl_cet(int option, u64 arg2);
> int cet_setup_shstk(void);
> int cet_setup_thread_shstk(struct task_struct *p, unsigned long clone_flags);
> void cet_disable_shstk(void);
> @@ -25,6 +27,7 @@ int cet_verify_rstor_token(bool ia32, unsigned long ssp, unsigned long *new_ssp)
> void cet_restore_signal(struct sc_ext *sc);
> int cet_setup_signal(bool ia32, unsigned long rstor, struct sc_ext *sc);
> #else
> +static inline int prctl_cet(int option, u64 arg2) { return -EINVAL; }
> static inline int cet_setup_thread_shstk(struct task_struct *p,
> unsigned long clone_flags) { return 0; }
> static inline void cet_disable_shstk(void) {}
> diff --git a/arch/x86/include/uapi/asm/prctl.h b/arch/x86/include/uapi/asm/prctl.h
> index 5a6aac9fa41f..9245bf629120 100644
> --- a/arch/x86/include/uapi/asm/prctl.h
> +++ b/arch/x86/include/uapi/asm/prctl.h
> @@ -14,4 +14,8 @@
> #define ARCH_MAP_VDSO_32 0x2002
> #define ARCH_MAP_VDSO_64 0x2003
>
> +#define ARCH_X86_CET_STATUS 0x3001
> +#define ARCH_X86_CET_DISABLE 0x3002
> +#define ARCH_X86_CET_LOCK 0x3003
> +
> #endif /* _ASM_X86_PRCTL_H */
> diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
> index 4a9a7e7d00dc..2f60a28769f9 100644
> --- a/arch/x86/kernel/Makefile
> +++ b/arch/x86/kernel/Makefile
> @@ -151,7 +151,7 @@ obj-$(CONFIG_UNWINDER_FRAME_POINTER) += unwind_frame.o
> obj-$(CONFIG_UNWINDER_GUESS) += unwind_guess.o
>
> obj-$(CONFIG_AMD_MEM_ENCRYPT) += sev-es.o
> -obj-$(CONFIG_X86_CET) += cet.o
> +obj-$(CONFIG_X86_CET) += cet.o cet_prctl.o
>
> ###
> # 64 bit specific files
> diff --git a/arch/x86/kernel/cet_prctl.c b/arch/x86/kernel/cet_prctl.c
> new file mode 100644
> index 000000000000..0030c63a08c0
> --- /dev/null
> +++ b/arch/x86/kernel/cet_prctl.c
> @@ -0,0 +1,60 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/errno.h>
> +#include <linux/uaccess.h>
> +#include <linux/prctl.h>
> +#include <linux/compat.h>
> +#include <linux/mman.h>
> +#include <linux/elfcore.h>
> +#include <linux/processor.h>
> +#include <asm/prctl.h>
> +#include <asm/cet.h>
> +
> +/* See Documentation/x86/intel_cet.rst. */
> +
> +static int cet_copy_status_to_user(struct cet_status *cet, u64 __user *ubuf)
> +{
> + u64 buf[3] = {};
> +
> + if (cet->shstk_size) {
> + buf[0] |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
> + buf[1] = cet->shstk_base;
> + buf[2] = cet->shstk_size;
> + }
> +
> + return copy_to_user(ubuf, buf, sizeof(buf));
> +}
> +
> +int prctl_cet(int option, u64 arg2)
> +{
> + struct cet_status *cet;
> +
> + if (!cpu_feature_enabled(X86_FEATURE_CET))
> + return -ENOTSUPP;
> +
> + cet = ¤t->thread.cet;
> +
> + if (option == ARCH_X86_CET_STATUS)
> + return cet_copy_status_to_user(cet, (u64 __user *)arg2);
> +
> + switch (option) {
> + case ARCH_X86_CET_DISABLE:
> + if (cet->locked)
> + return -EPERM;
> +
> + if (arg2 & ~GNU_PROPERTY_X86_FEATURE_1_VALID)
> + return -EINVAL;
> + if (arg2 & GNU_PROPERTY_X86_FEATURE_1_SHSTK)
> + cet_disable_shstk();
> + return 0;
> +
> + case ARCH_X86_CET_LOCK:
> + if (arg2)
> + return -EINVAL;
> + cet->locked = 1;
> + return 0;
> +
> + default:
> + return -ENOSYS;
> + }
> +}
> diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
> index 3af6b36e1a5c..9e11e5f589f3 100644
> --- a/arch/x86/kernel/process.c
> +++ b/arch/x86/kernel/process.c
> @@ -979,14 +979,14 @@ unsigned long get_wchan(struct task_struct *p)
> }
>
> long do_arch_prctl_common(struct task_struct *task, int option,
> - unsigned long cpuid_enabled)
> + unsigned long arg2)
> {
> switch (option) {
> case ARCH_GET_CPUID:
> return get_cpuid_mode();
> case ARCH_SET_CPUID:
> - return set_cpuid_mode(task, cpuid_enabled);
> + return set_cpuid_mode(task, arg2);
> }
>
> - return -EINVAL;
> + return prctl_cet(option, arg2);
> }
> --
> 2.21.0
>
>
--
Kees Cook
next prev parent reply other threads:[~2021-02-04 20:37 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-03 22:55 [PATCH v19 00/25] Control-flow Enforcement: Shadow Stack Yu-cheng Yu
2021-02-03 22:55 ` [PATCH v19 01/25] Documentation/x86: Add CET description Yu-cheng Yu
2021-02-04 19:52 ` Kees Cook
2021-02-04 20:03 ` Yu, Yu-cheng
2021-02-03 22:55 ` [PATCH v19 02/25] x86/cet/shstk: Add Kconfig option for user-mode control-flow protection Yu-cheng Yu
2021-02-04 19:56 ` Kees Cook
2021-02-05 0:05 ` Yu, Yu-cheng
2021-02-03 22:55 ` [PATCH v19 03/25] x86/cpufeatures: Add CET CPU feature flags for Control-flow Enforcement Technology (CET) Yu-cheng Yu
2021-02-04 19:57 ` Kees Cook
2021-02-03 22:55 ` [PATCH v19 04/25] x86/cpufeatures: Introduce X86_FEATURE_CET and setup functions Yu-cheng Yu
2021-02-04 19:58 ` Kees Cook
2021-02-05 13:43 ` Borislav Petkov
2021-02-05 16:15 ` Yu, Yu-cheng
2021-02-03 22:55 ` [PATCH v19 05/25] x86/fpu/xstate: Introduce CET MSR and XSAVES supervisor states Yu-cheng Yu
2021-02-04 19:59 ` Kees Cook
2021-02-03 22:55 ` [PATCH v19 06/25] x86/cet: Add control-protection fault handler Yu-cheng Yu
2021-02-04 20:09 ` Kees Cook
2021-02-05 0:10 ` Yu, Yu-cheng
2021-02-05 13:59 ` Borislav Petkov
2021-02-05 18:00 ` Yu, Yu-cheng
2021-02-05 18:29 ` Kees Cook
2021-02-08 18:20 ` Borislav Petkov
2021-02-08 18:50 ` Yu, Yu-cheng
2021-02-08 18:53 ` Borislav Petkov
2021-02-08 19:23 ` Yu, Yu-cheng
2021-02-08 19:48 ` Borislav Petkov
2021-02-08 20:11 ` Yu, Yu-cheng
2021-02-03 22:55 ` [PATCH v19 07/25] x86/mm: Remove _PAGE_DIRTY from kernel RO pages Yu-cheng Yu
2021-02-04 20:10 ` Kees Cook
2021-02-03 22:55 ` [PATCH v19 08/25] x86/mm: Introduce _PAGE_COW Yu-cheng Yu
2021-02-04 20:19 ` Kees Cook
2021-02-04 20:27 ` Dave Hansen
2021-02-05 18:41 ` Yu, Yu-cheng
2021-02-08 23:03 ` Yu, Yu-cheng
2021-02-05 18:58 ` Yu, Yu-cheng
2021-02-03 22:55 ` [PATCH v19 09/25] drm/i915/gvt: Change _PAGE_DIRTY to _PAGE_DIRTY_BITS Yu-cheng Yu
2021-02-03 22:55 ` [PATCH v19 10/25] x86/mm: Update pte_modify for _PAGE_COW Yu-cheng Yu
2021-02-04 20:20 ` Kees Cook
2021-02-03 22:55 ` [PATCH v19 11/25] x86/mm: Update ptep_set_wrprotect() and pmdp_set_wrprotect() for transition from _PAGE_DIRTY to _PAGE_COW Yu-cheng Yu
2021-02-04 20:21 ` Kees Cook
2021-02-03 22:55 ` [PATCH v19 12/25] mm: Introduce VM_SHSTK for shadow stack memory Yu-cheng Yu
2021-02-04 20:46 ` Cyrill Gorcunov
2021-02-04 21:48 ` Yu, Yu-cheng
2021-02-03 22:55 ` [PATCH v19 13/25] x86/mm: Shadow Stack page fault error checking Yu-cheng Yu
2021-02-03 22:55 ` [PATCH v19 14/25] x86/mm: Update maybe_mkwrite() for shadow stack Yu-cheng Yu
2021-02-04 20:22 ` Kees Cook
2021-02-03 22:55 ` [PATCH v19 15/25] mm: Fixup places that call pte_mkwrite() directly Yu-cheng Yu
2021-02-04 20:22 ` Kees Cook
2021-02-03 22:55 ` [PATCH v19 16/25] mm: Add guard pages around a shadow stack Yu-cheng Yu
2021-02-04 20:24 ` Kees Cook
2021-02-03 22:55 ` [PATCH v19 17/25] mm/mmap: Add shadow stack pages to memory accounting Yu-cheng Yu
2021-02-04 20:24 ` Kees Cook
2021-02-03 22:55 ` [PATCH v19 18/25] mm: Update can_follow_write_pte() for shadow stack Yu-cheng Yu
2021-02-04 20:27 ` Kees Cook
2021-02-03 22:55 ` [PATCH v19 19/25] mm: Re-introduce vm_flags to do_mmap() Yu-cheng Yu
2021-02-04 20:28 ` Kees Cook
2021-02-03 22:55 ` [PATCH v19 20/25] x86/cet/shstk: User-mode shadow stack support Yu-cheng Yu
2021-02-04 20:29 ` Kees Cook
2021-02-03 22:55 ` [PATCH v19 21/25] x86/cet/shstk: Handle signals for shadow stack Yu-cheng Yu
2021-02-03 22:55 ` [PATCH v19 22/25] ELF: Introduce arch_setup_elf_property() Yu-cheng Yu
2021-02-04 20:33 ` Kees Cook
2021-02-03 22:55 ` [PATCH v19 23/25] x86/cet/shstk: Handle thread shadow stack Yu-cheng Yu
2021-02-03 22:55 ` [PATCH v19 24/25] x86/cet/shstk: Add arch_prctl functions for " Yu-cheng Yu
2021-02-04 20:35 ` Kees Cook [this message]
2021-02-04 23:41 ` Yu, Yu-cheng
2021-02-05 18:26 ` Kees Cook
2021-02-03 22:55 ` [PATCH v19 25/25] mm: Introduce PROT_SHSTK " Yu-cheng Yu
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