From: Jann Horn <jannh@google.com> To: yu-cheng.yu@intel.com Cc: "the arch/x86 maintainers" <x86@kernel.org>, "H . Peter Anvin" <hpa@zytor.com>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, kernel list <linux-kernel@vger.kernel.org>, linux-doc@vger.kernel.org, Linux-MM <linux-mm@kvack.org>, linux-arch <linux-arch@vger.kernel.org>, Linux API <linux-api@vger.kernel.org>, Arnd Bergmann <arnd@arndb.de>, Andy Lutomirski <luto@amacapital.net>, Balbir Singh <bsingharora@gmail.com>, Cyrill Gorcunov <gorcunov@gmail.com>, Dave Hansen <dave.hansen@linux.intel.com>, Florian Weimer <fweimer@redhat.com>, hjl.tools@gmail.com, Jonathan Corbet <corbet@lwn.net>, keescook@chromiun.org, 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>, ravi.v.shankar@intel.com, vedvyas.shanbhogue@intel.com Subject: Re: [RFC PATCH v3 18/24] x86/cet/shstk: User-mode shadow stack support Date: Thu, 30 Aug 2018 18:10:17 +0200 [thread overview] Message-ID: <CAG48ez0d8+E_O-9u6ZHZ6dQO55Ui2ydV_kia-EEhyYeB_w4r2g@mail.gmail.com> (raw) In-Reply-To: <20180830143904.3168-19-yu-cheng.yu@intel.com> On Thu, Aug 30, 2018 at 4:44 PM Yu-cheng Yu <yu-cheng.yu@intel.com> wrote: > > This patch adds basic shadow stack enabling/disabling routines. > A task's shadow stack is allocated from memory with VM_SHSTK > flag set and read-only protection. The shadow stack is > allocated to a fixed size of RLIMIT_STACK. > > Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com> [...] > +static int set_shstk_ptr(unsigned long addr) > +{ > + u64 r; > + > + if (!cpu_feature_enabled(X86_FEATURE_SHSTK)) > + return -1; > + > + if ((addr >= TASK_SIZE_MAX) || (!IS_ALIGNED(addr, 4))) > + return -1; > + > + rdmsrl(MSR_IA32_U_CET, r); > + wrmsrl(MSR_IA32_PL3_SSP, addr); > + wrmsrl(MSR_IA32_U_CET, r | MSR_IA32_CET_SHSTK_EN); > + return 0; > +} Here's a really stupid question: Where is the logic for switching those MSRs on task switch? MSR_IA32_PL3_SSP contains a userspace pointer, so it has to be switched on task switch, right? I'm sure I'm missing something obvious, but grepping for places that set MSR_IA32_PL3_SSP to nonzero values through the entire patchset, I only see set_shstk_ptr(), which is called from: - cet_setup_shstk() (called from arch_setup_features(), which is called from load_elf_binary()) - cet_restore_signal() (called on signal handler return) - cet_setup_signal() (called from signal handling code)
WARNING: multiple messages have this Message-ID (diff)
From: Jann Horn <jannh@google.com> To: yu-cheng.yu@intel.com Cc: the arch/x86 maintainers <x86@kernel.org>, "H . Peter Anvin" <hpa@zytor.com>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, kernel list <linux-kernel@vger.kernel.org>, linux-doc@vger.kernel.org, Linux-MM <linux-mm@kvack.org>, linux-arch <linux-arch@vger.kernel.org>, Linux API <linux-api@vger.kernel.org>, Arnd Bergmann <arnd@arndb.de>, Andy Lutomirski <luto@amacapital.net>, Balbir Singh <bsingharora@gmail.com>, Cyrill Gorcunov <gorcunov@gmail.com>, Dave Hansen <dave.hansen@linux.intel.com>, Florian Weimer <fweimer@redhat.com>, hjl.tools@gmail.com, Jonathan Corbet <corbet@lwn.net>, keescook@chromiun.org, Mike Kravetz <mike.kravetz@oracle.com>, Nadav Amit <nadav.amit@gmail.com>, Oleg Nesterov <oleg@redhat.com>Pavel Machek <pa> Subject: Re: [RFC PATCH v3 18/24] x86/cet/shstk: User-mode shadow stack support Date: Thu, 30 Aug 2018 18:10:17 +0200 [thread overview] Message-ID: <CAG48ez0d8+E_O-9u6ZHZ6dQO55Ui2ydV_kia-EEhyYeB_w4r2g@mail.gmail.com> (raw) In-Reply-To: <20180830143904.3168-19-yu-cheng.yu@intel.com> On Thu, Aug 30, 2018 at 4:44 PM Yu-cheng Yu <yu-cheng.yu@intel.com> wrote: > > This patch adds basic shadow stack enabling/disabling routines. > A task's shadow stack is allocated from memory with VM_SHSTK > flag set and read-only protection. The shadow stack is > allocated to a fixed size of RLIMIT_STACK. > > Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com> [...] > +static int set_shstk_ptr(unsigned long addr) > +{ > + u64 r; > + > + if (!cpu_feature_enabled(X86_FEATURE_SHSTK)) > + return -1; > + > + if ((addr >= TASK_SIZE_MAX) || (!IS_ALIGNED(addr, 4))) > + return -1; > + > + rdmsrl(MSR_IA32_U_CET, r); > + wrmsrl(MSR_IA32_PL3_SSP, addr); > + wrmsrl(MSR_IA32_U_CET, r | MSR_IA32_CET_SHSTK_EN); > + return 0; > +} Here's a really stupid question: Where is the logic for switching those MSRs on task switch? MSR_IA32_PL3_SSP contains a userspace pointer, so it has to be switched on task switch, right? I'm sure I'm missing something obvious, but grepping for places that set MSR_IA32_PL3_SSP to nonzero values through the entire patchset, I only see set_shstk_ptr(), which is called from: - cet_setup_shstk() (called from arch_setup_features(), which is called from load_elf_binary()) - cet_restore_signal() (called on signal handler return) - cet_setup_signal() (called from signal handling code)
next prev parent reply other threads:[~2018-08-30 16:10 UTC|newest] Thread overview: 167+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-08-30 14:38 [RFC PATCH v3 00/24] Control Flow Enforcement: Shadow Stack Yu-cheng Yu 2018-08-30 14:38 ` Yu-cheng Yu 2018-08-30 14:38 ` [RFC PATCH v3 01/24] x86/cpufeatures: Add CPUIDs for Control-flow Enforcement Technology (CET) Yu-cheng Yu 2018-08-30 14:38 ` Yu-cheng Yu 2018-08-30 14:38 ` [RFC PATCH v3 02/24] x86/fpu/xstate: Change some names to separate XSAVES system and user states Yu-cheng Yu 2018-08-30 14:38 ` Yu-cheng Yu 2018-08-30 14:38 ` [RFC PATCH v3 03/24] x86/fpu/xstate: Enable XSAVES system states Yu-cheng Yu 2018-08-30 14:38 ` Yu-cheng Yu 2018-08-30 14:38 ` [RFC PATCH v3 04/24] x86/fpu/xstate: Add XSAVES system states for shadow stack Yu-cheng Yu 2018-08-30 14:38 ` Yu-cheng Yu 2018-08-30 14:38 ` [RFC PATCH v3 05/24] Documentation/x86: Add CET description Yu-cheng Yu 2018-08-30 14:38 ` Yu-cheng Yu 2018-08-30 20:39 ` Pavel Machek 2018-08-30 20:39 ` Pavel Machek 2018-08-30 22:49 ` Yu-cheng Yu 2018-08-30 22:49 ` Yu-cheng Yu 2018-08-30 22:49 ` Yu-cheng Yu 2018-09-14 21:17 ` Yu-cheng Yu 2018-09-14 21:17 ` Yu-cheng Yu 2018-09-14 21:17 ` Yu-cheng Yu 2018-09-03 2:56 ` Randy Dunlap 2018-09-03 2:56 ` Randy Dunlap 2018-08-30 14:38 ` [RFC PATCH v3 06/24] x86/cet: Control protection exception handler Yu-cheng Yu 2018-08-30 14:38 ` Yu-cheng Yu 2018-08-31 15:01 ` Jann Horn 2018-08-31 15:01 ` Jann Horn 2018-08-31 16:20 ` Yu-cheng Yu 2018-08-31 16:20 ` Yu-cheng Yu 2018-08-31 16:20 ` Yu-cheng Yu 2018-08-30 14:38 ` [RFC PATCH v3 07/24] x86/cet/shstk: Add Kconfig option for user-mode shadow stack Yu-cheng Yu 2018-08-30 14:38 ` Yu-cheng Yu 2018-08-30 14:38 ` [RFC PATCH v3 08/24] mm: Introduce VM_SHSTK for shadow stack memory Yu-cheng Yu 2018-08-30 14:38 ` Yu-cheng Yu 2018-08-30 14:38 ` [RFC PATCH v3 09/24] x86/mm: Change _PAGE_DIRTY to _PAGE_DIRTY_HW Yu-cheng Yu 2018-08-30 14:38 ` Yu-cheng Yu 2018-08-30 14:38 ` [RFC PATCH v3 10/24] x86/mm: Introduce _PAGE_DIRTY_SW Yu-cheng Yu 2018-08-30 14:38 ` Yu-cheng Yu 2018-08-30 14:38 ` [RFC PATCH v3 11/24] drm/i915/gvt: Update _PAGE_DIRTY to _PAGE_DIRTY_BITS Yu-cheng Yu 2018-08-30 14:38 ` Yu-cheng Yu 2018-08-30 14:38 ` [RFC PATCH v3 12/24] x86/mm: Modify ptep_set_wrprotect and pmdp_set_wrprotect for _PAGE_DIRTY_SW Yu-cheng Yu 2018-08-30 14:38 ` Yu-cheng Yu 2018-08-30 15:49 ` Jann Horn 2018-08-30 15:49 ` Jann Horn 2018-08-30 16:02 ` Yu-cheng Yu 2018-08-30 16:02 ` Yu-cheng Yu 2018-08-30 16:02 ` Yu-cheng Yu 2018-08-30 16:08 ` Dave Hansen 2018-08-30 16:08 ` Dave Hansen 2018-08-30 16:23 ` Jann Horn 2018-08-30 16:23 ` Jann Horn 2018-08-30 17:19 ` Dave Hansen 2018-08-30 17:19 ` Dave Hansen 2018-08-30 17:26 ` Yu-cheng Yu 2018-08-30 17:26 ` Yu-cheng Yu 2018-08-30 17:26 ` Yu-cheng Yu 2018-08-30 17:33 ` Dave Hansen 2018-08-30 17:33 ` Dave Hansen 2018-08-30 17:54 ` Yu-cheng Yu 2018-08-30 17:54 ` Yu-cheng Yu 2018-08-30 17:54 ` Yu-cheng Yu 2018-08-30 17:59 ` Jann Horn 2018-08-30 17:59 ` Jann Horn 2018-08-30 20:21 ` Yu-cheng Yu 2018-08-30 20:21 ` Yu-cheng Yu 2018-08-30 20:21 ` Yu-cheng Yu 2018-08-30 20:44 ` Jann Horn 2018-08-30 20:44 ` Jann Horn 2018-08-30 20:52 ` Yu-cheng Yu 2018-08-30 20:52 ` Yu-cheng Yu 2018-08-30 20:52 ` Yu-cheng Yu 2018-08-30 21:01 ` Jann Horn 2018-08-30 21:01 ` Jann Horn 2018-08-30 21:47 ` Jann Horn 2018-08-30 21:47 ` Jann Horn 2018-08-31 9:53 ` Peter Zijlstra 2018-08-31 9:53 ` Peter Zijlstra 2018-08-31 14:33 ` Yu-cheng Yu 2018-08-31 14:33 ` Yu-cheng Yu 2018-08-31 14:33 ` Yu-cheng Yu 2018-08-31 14:47 ` Dave Hansen 2018-08-31 14:47 ` Dave Hansen 2018-08-31 15:48 ` Yu-cheng Yu 2018-08-31 15:48 ` Yu-cheng Yu 2018-08-31 15:48 ` Yu-cheng Yu 2018-08-31 15:58 ` Dave Hansen 2018-08-31 15:58 ` Dave Hansen 2018-08-31 16:29 ` Peter Zijlstra 2018-08-31 16:29 ` Peter Zijlstra 2018-09-14 20:39 ` Yu-cheng Yu 2018-09-14 20:39 ` Yu-cheng Yu 2018-09-14 20:39 ` Yu-cheng Yu 2018-09-14 20:46 ` Dave Hansen 2018-09-14 20:46 ` Dave Hansen 2018-09-14 20:46 ` Dave Hansen 2018-09-14 21:08 ` Yu-cheng Yu 2018-09-14 21:08 ` Yu-cheng Yu 2018-09-14 21:08 ` Yu-cheng Yu 2018-09-14 21:33 ` Dave Hansen 2018-09-14 21:33 ` Dave Hansen 2018-09-14 21:33 ` Dave Hansen 2018-08-31 1:23 ` Andy Lutomirski 2018-08-31 1:23 ` Andy Lutomirski 2018-08-30 17:34 ` Andy Lutomirski 2018-08-30 17:34 ` Andy Lutomirski 2018-08-30 18:55 ` Dave Hansen 2018-08-30 18:55 ` Dave Hansen 2018-08-31 17:46 ` Andy Lutomirski 2018-08-31 17:46 ` Andy Lutomirski 2018-08-31 17:52 ` Dave Hansen 2018-08-31 17:52 ` Dave Hansen 2018-08-31 17:52 ` Dave Hansen 2018-08-30 19:59 ` Randy Dunlap 2018-08-30 19:59 ` Randy Dunlap 2018-08-30 20:23 ` Yu-cheng Yu 2018-08-30 20:23 ` Yu-cheng Yu 2018-08-30 20:23 ` Yu-cheng Yu 2018-08-31 16:29 ` Dave Hansen 2018-08-31 16:29 ` Dave Hansen 2018-08-30 14:38 ` [RFC PATCH v3 13/24] x86/mm: Shadow stack page fault error checking Yu-cheng Yu 2018-08-30 14:38 ` Yu-cheng Yu 2018-08-30 14:38 ` [RFC PATCH v3 14/24] mm: Handle shadow stack page fault Yu-cheng Yu 2018-08-30 14:38 ` Yu-cheng Yu 2018-08-30 14:38 ` [RFC PATCH v3 15/24] mm: Handle THP/HugeTLB " Yu-cheng Yu 2018-08-30 14:38 ` Yu-cheng Yu 2018-08-30 14:38 ` [RFC PATCH v3 16/24] mm: Update can_follow_write_pte/pmd for shadow stack Yu-cheng Yu 2018-08-30 14:38 ` Yu-cheng Yu 2018-08-30 14:38 ` [RFC PATCH v3 17/24] mm: Introduce do_mmap_locked() Yu-cheng Yu 2018-08-30 14:38 ` Yu-cheng Yu 2018-08-30 14:38 ` [RFC PATCH v3 18/24] x86/cet/shstk: User-mode shadow stack support Yu-cheng Yu 2018-08-30 14:38 ` Yu-cheng Yu 2018-08-30 16:10 ` Jann Horn [this message] 2018-08-30 16:10 ` Jann Horn 2018-08-30 16:20 ` Yu-cheng Yu 2018-08-30 16:20 ` Yu-cheng Yu 2018-08-30 16:20 ` Yu-cheng Yu 2018-08-30 14:38 ` [RFC PATCH v3 19/24] x86/cet/shstk: Introduce WRUSS instruction Yu-cheng Yu 2018-08-30 14:38 ` Yu-cheng Yu 2018-08-30 15:39 ` Jann Horn 2018-08-30 15:39 ` Jann Horn 2018-08-30 15:55 ` Andy Lutomirski 2018-08-30 15:55 ` Andy Lutomirski 2018-08-30 16:22 ` Yu-cheng Yu 2018-08-30 16:22 ` Yu-cheng Yu 2018-08-30 16:22 ` Yu-cheng Yu 2018-08-31 21:49 ` Yu-cheng Yu 2018-08-31 21:49 ` Yu-cheng Yu 2018-08-31 21:49 ` Yu-cheng Yu 2018-08-31 22:16 ` Andy Lutomirski 2018-08-31 22:16 ` Andy Lutomirski 2018-09-14 20:46 ` Yu-cheng Yu 2018-09-14 20:46 ` Yu-cheng Yu 2018-09-14 20:46 ` Yu-cheng Yu 2018-08-30 14:39 ` [RFC PATCH v3 20/24] x86/cet/shstk: Signal handling for shadow stack Yu-cheng Yu 2018-08-30 14:39 ` Yu-cheng Yu 2018-08-30 14:39 ` [RFC PATCH v3 21/24] x86/cet/shstk: ELF header parsing of Shadow Stack Yu-cheng Yu 2018-08-30 14:39 ` Yu-cheng Yu 2018-08-30 14:39 ` [RFC PATCH v3 22/24] x86/cet/shstk: Handle thread shadow stack Yu-cheng Yu 2018-08-30 14:39 ` Yu-cheng Yu 2018-08-30 14:39 ` [RFC PATCH v3 23/24] x86/cet/shstk: Add arch_prctl functions for Shadow Stack Yu-cheng Yu 2018-08-30 14:39 ` Yu-cheng Yu 2018-08-30 14:39 ` [RFC PATCH v3 24/24] x86/cet/shstk: Add Shadow Stack instructions to opcode map Yu-cheng Yu 2018-08-30 14:39 ` Yu-cheng Yu 2018-09-02 8:13 ` [RFC PATCH v3 00/24] Control Flow Enforcement: Shadow Stack Balbir Singh 2018-09-02 8:13 ` Balbir Singh 2018-09-04 14:47 ` Yu-cheng Yu 2018-09-04 14:47 ` Yu-cheng Yu 2018-09-04 14:47 ` Yu-cheng Yu
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