From patchwork Thu Jul 22 20:52:14 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yu-cheng Yu X-Patchwork-Id: 12394733 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B9057C00143 for ; Thu, 22 Jul 2021 20:53:58 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 4FE4760EB5 for ; Thu, 22 Jul 2021 20:53:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 4FE4760EB5 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 678538E0014; Thu, 22 Jul 2021 16:53:09 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5B4F68E0012; Thu, 22 Jul 2021 16:53:09 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2A71C8E0016; Thu, 22 Jul 2021 16:53:09 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0166.hostedemail.com [216.40.44.166]) by kanga.kvack.org (Postfix) with ESMTP id DA1488E0012 for ; Thu, 22 Jul 2021 16:53:08 -0400 (EDT) Received: from smtpin40.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 96CC5181AEF3E for ; Thu, 22 Jul 2021 20:53:08 +0000 (UTC) X-FDA: 78391423656.40.06F56A4 Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by imf24.hostedemail.com (Postfix) with ESMTP id BEA59B001BE7 for ; Thu, 22 Jul 2021 20:53:07 +0000 (UTC) X-IronPort-AV: E=McAfee;i="6200,9189,10053"; a="209845116" X-IronPort-AV: E=Sophos;i="5.84,262,1620716400"; d="scan'208";a="209845116" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Jul 2021 13:53:04 -0700 X-IronPort-AV: E=Sophos;i="5.84,262,1620716400"; d="scan'208";a="502035516" Received: from yyu32-desk.sc.intel.com ([143.183.136.146]) by fmsmga003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Jul 2021 13:53:03 -0700 From: Yu-cheng Yu To: x86@kernel.org, "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , 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 , Andy Lutomirski , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , Weijiang Yang , Pengfei Xu , Haitao Huang , Rick P Edgecombe Cc: Yu-cheng Yu Subject: [PATCH v28 27/32] x86/cet/shstk: Handle signals for shadow stack Date: Thu, 22 Jul 2021 13:52:14 -0700 Message-Id: <20210722205219.7934-28-yu-cheng.yu@intel.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20210722205219.7934-1-yu-cheng.yu@intel.com> References: <20210722205219.7934-1-yu-cheng.yu@intel.com> MIME-Version: 1.0 Authentication-Results: imf24.hostedemail.com; dkim=none; spf=none (imf24.hostedemail.com: domain of yu-cheng.yu@intel.com has no SPF policy when checking 192.55.52.120) smtp.mailfrom=yu-cheng.yu@intel.com; dmarc=fail reason="No valid SPF, No valid DKIM" header.from=intel.com (policy=none) X-Rspamd-Server: rspam05 X-Stat-Signature: esdpizuekyj87id5ro95h5t3tmd6t1iq X-Rspamd-Queue-Id: BEA59B001BE7 X-HE-Tag: 1626987187-293914 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: A signal handler (if not changing ucontext) returns to the restorer, and the restorer calls sigreturn. Thus, when setting up a signal frame, the kernel: - installs a shadow stack restore token pointing to the current shadow stack address, and - installs the restorer address below the restore token. In sigreturn, the restore token is verified and shadow stack pointer is restored. Signed-off-by: Yu-cheng Yu Cc: Andy Lutomirski Cc: Cyrill Gorcunov Cc: Florian Weimer Cc: H. Peter Anvin Cc: Kees Cook --- v27: - Eliminate saving shadow stack pointer to signal context. v25: - Update commit log/comments for the sc_ext struct. - Use restorer address already calculated. - Change CONFIG_X86_CET to CONFIG_X86_SHADOW_STACK. - Change X86_FEATURE_CET to X86_FEATURE_SHSTK. - Eliminate writing to MSR_IA32_U_CET for shadow stack. - Change wrmsrl() to wrmsrl_safe() and handle error. arch/x86/ia32/ia32_signal.c | 25 +++++++++++++++++----- arch/x86/include/asm/cet.h | 4 ++++ arch/x86/kernel/shstk.c | 42 +++++++++++++++++++++++++++++++++++++ arch/x86/kernel/signal.c | 13 ++++++++++++ 4 files changed, 79 insertions(+), 5 deletions(-) diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c index 5e3d9b7fd5fb..d7a30bc98e66 100644 --- a/arch/x86/ia32/ia32_signal.c +++ b/arch/x86/ia32/ia32_signal.c @@ -35,6 +35,7 @@ #include #include #include +#include static inline void reload_segments(struct sigcontext_32 *sc) { @@ -113,6 +114,10 @@ COMPAT_SYSCALL_DEFINE0(sigreturn) if (ia32_restore_sigcontext(regs, &frame->sc)) goto badframe; + + if (restore_signal_shadow_stack()) + goto badframe; + return regs->ax; badframe: @@ -138,6 +143,9 @@ COMPAT_SYSCALL_DEFINE0(rt_sigreturn) if (ia32_restore_sigcontext(regs, &frame->uc.uc_mcontext)) goto badframe; + if (restore_signal_shadow_stack()) + goto badframe; + if (compat_restore_altstack(&frame->uc.uc_stack)) goto badframe; @@ -262,6 +270,9 @@ int ia32_setup_frame(int sig, struct ksignal *ksig, restorer = &frame->retcode; } + if (setup_signal_shadow_stack(1, restorer)) + return -EFAULT; + if (!user_access_begin(frame, sizeof(*frame))) return -EFAULT; @@ -319,6 +330,15 @@ int ia32_setup_rt_frame(int sig, struct ksignal *ksig, frame = get_sigframe(ksig, regs, sizeof(*frame), &fp); + if (ksig->ka.sa.sa_flags & SA_RESTORER) + restorer = ksig->ka.sa.sa_restorer; + else + restorer = current->mm->context.vdso + + vdso_image_32.sym___kernel_rt_sigreturn; + + if (setup_signal_shadow_stack(1, restorer)) + return -EFAULT; + if (!user_access_begin(frame, sizeof(*frame))) return -EFAULT; @@ -334,11 +354,6 @@ int ia32_setup_rt_frame(int sig, struct ksignal *ksig, unsafe_put_user(0, &frame->uc.uc_link, Efault); unsafe_compat_save_altstack(&frame->uc.uc_stack, regs->sp, Efault); - if (ksig->ka.sa.sa_flags & SA_RESTORER) - restorer = ksig->ka.sa.sa_restorer; - else - restorer = current->mm->context.vdso + - vdso_image_32.sym___kernel_rt_sigreturn; unsafe_put_user(ptr_to_compat(restorer), &frame->pretcode, Efault); /* diff --git a/arch/x86/include/asm/cet.h b/arch/x86/include/asm/cet.h index aa533700ba31..2f7940d68ce3 100644 --- a/arch/x86/include/asm/cet.h +++ b/arch/x86/include/asm/cet.h @@ -24,6 +24,8 @@ void shstk_disable(void); int shstk_setup_rstor_token(bool ia32, unsigned long restorer, unsigned long *new_ssp); int shstk_check_rstor_token(bool ia32, unsigned long *new_ssp); +int setup_signal_shadow_stack(int ia32, void __user *restorer); +int restore_signal_shadow_stack(void); #else static inline int shstk_setup(void) { return 0; } static inline int shstk_alloc_thread_stack(struct task_struct *p, @@ -35,6 +37,8 @@ static inline int shstk_setup_rstor_token(bool ia32, unsigned long restorer, unsigned long *new_ssp) { return 0; } static inline int shstk_check_rstor_token(bool ia32, unsigned long *new_ssp) { return 0; } +static inline int setup_signal_shadow_stack(int ia32, void __user *restorer) { return 0; } +static inline int restore_signal_shadow_stack(void) { return 0; } #endif #endif /* __ASSEMBLY__ */ diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c index 89c7da3cdb92..b3d64cfa28eb 100644 --- a/arch/x86/kernel/shstk.c +++ b/arch/x86/kernel/shstk.c @@ -331,3 +331,45 @@ int shstk_check_rstor_token(bool proc32, unsigned long *new_ssp) return 0; } + +int setup_signal_shadow_stack(int ia32, void __user *restorer) +{ + struct thread_shstk *shstk = ¤t->thread.shstk; + unsigned long new_ssp; + int err; + + if (!cpu_feature_enabled(X86_FEATURE_SHSTK) || !shstk->size) + return 0; + + err = shstk_setup_rstor_token(ia32, (unsigned long)restorer, + &new_ssp); + if (err) + return err; + + start_update_msrs(); + err = wrmsrl_safe(MSR_IA32_PL3_SSP, new_ssp); + end_update_msrs(); + + return err; +} + +int restore_signal_shadow_stack(void) +{ + struct thread_shstk *shstk = ¤t->thread.shstk; + int ia32 = in_ia32_syscall(); + unsigned long new_ssp; + int err; + + if (!cpu_feature_enabled(X86_FEATURE_SHSTK) || !shstk->size) + return 0; + + err = shstk_check_rstor_token(ia32, &new_ssp); + if (err) + return err; + + start_update_msrs(); + err = wrmsrl_safe(MSR_IA32_PL3_SSP, new_ssp); + end_update_msrs(); + + return err; +} diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c index f4d21e470083..661e46803b84 100644 --- a/arch/x86/kernel/signal.c +++ b/arch/x86/kernel/signal.c @@ -46,6 +46,7 @@ #include #include #include +#include #ifdef CONFIG_X86_64 /* @@ -471,6 +472,9 @@ static int __setup_rt_frame(int sig, struct ksignal *ksig, frame = get_sigframe(&ksig->ka, regs, sizeof(struct rt_sigframe), &fp); uc_flags = frame_uc_flags(regs); + if (setup_signal_shadow_stack(0, ksig->ka.sa.sa_restorer)) + return -EFAULT; + if (!user_access_begin(frame, sizeof(*frame))) return -EFAULT; @@ -576,6 +580,9 @@ static int x32_setup_rt_frame(struct ksignal *ksig, uc_flags = frame_uc_flags(regs); + if (setup_signal_shadow_stack(0, ksig->ka.sa.sa_restorer)) + return -EFAULT; + if (!user_access_begin(frame, sizeof(*frame))) return -EFAULT; @@ -674,6 +681,9 @@ SYSCALL_DEFINE0(rt_sigreturn) if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags)) goto badframe; + if (restore_signal_shadow_stack()) + goto badframe; + if (restore_altstack(&frame->uc.uc_stack)) goto badframe; @@ -932,6 +942,9 @@ COMPAT_SYSCALL_DEFINE0(x32_rt_sigreturn) if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags)) goto badframe; + if (restore_signal_shadow_stack()) + goto badframe; + if (compat_restore_altstack(&frame->uc.uc_stack)) goto badframe;