From mboxrd@z Thu Jan 1 00:00:00 1970 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=-8.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, T_DKIMWL_WL_MED,URIBL_BLOCKED,USER_IN_DEF_DKIM_WL autolearn=ham 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 11F1DC433F4 for ; Fri, 31 Aug 2018 15:02:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8DB842077C for ; Fri, 31 Aug 2018 15:02:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="KE0f1wy7" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8DB842077C Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728947AbeHaTKD (ORCPT ); Fri, 31 Aug 2018 15:10:03 -0400 Received: from mail-oi0-f68.google.com ([209.85.218.68]:41597 "EHLO mail-oi0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728932AbeHaTKD (ORCPT ); Fri, 31 Aug 2018 15:10:03 -0400 Received: by mail-oi0-f68.google.com with SMTP id k12-v6so22180382oiw.8 for ; Fri, 31 Aug 2018 08:02:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=VO1E65e+iHvRxpquck2xT3J8OTN9faM6zLPXFDpjCFE=; b=KE0f1wy7aQu3+/DiQRcjwRuwoAi5YWJrZYNr3MFH6SHlkv+qioQfX3RRTGV3NHKGNV ywYYDtYwPYcIuP3Ta8BdGFE/odkDMGmjurpeRXADQLak1AbZLbBFqkuz6+Itla2B3rYS QWX4c0NhXkebRkKTivKDLJ54Re9besWKF0kVSB1Q5K9SU5UwsakeP3AgvTMe1j8i0ZAT 1FdYRHITy9tRZgRkseRHZcWD3dCcWvcsVuTlaq4IbLSZ82XL3DEcY/KkM8pXWUc0jGSC iFKYTFzT4LUqdjssoXQsQ+I7Co0of3/WUo1tPMUynTMz/RH7LBnl+cNPOUy9K4Fpnm5c iTLA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=VO1E65e+iHvRxpquck2xT3J8OTN9faM6zLPXFDpjCFE=; b=o9ydkD2fFOaErm97VdaziG2gCjj8gmHqWup2nlFNQbfT/4uYPRhI526Xmp5COHfYqo ZT638UbODZSAlnytYLH48gcGWWb++cu9hKuIl41pj2cC6W+uFVgHC9avQ2SFfZna7aOe jN0MTpxjbjxCzNQexoftFPjnPYFuiYli+GXdHHiaVozJQzAwoiYETf/GdN3FAp8RX55m IzMWZ4qbboL9boNTrb3xm0Bl844YrOBcDzIxcJIQkQy1lageQu+wgsC7z2/3foCmZrUr DGCMZmSPWx5LsdL8YOLWi+CTNx032gDyFo3FxmaFAHz8NyGMbV+0VOj4ch/hB95is0c6 TMww== X-Gm-Message-State: APzg51AyGNWvn/oA6LOwubHWXdjxRsSPnSq4zKkmp3aVpIFNHgEL8JLH r51C7pCyCYnWAtNfWsRqlTHLG9pbYYNx+VW9ekQU0g== X-Google-Smtp-Source: ANB0Vdb1kP1C9qHD1EqBYR6Udetv/8kjc8hQgxiuv5REDY/mN+1HoCDAViwbzbvhZ79vZhl4MTnJVb01r8PyYDN9Gi8= X-Received: by 2002:aca:dc55:: with SMTP id t82-v6mr6919903oig.159.1535727729152; Fri, 31 Aug 2018 08:02:09 -0700 (PDT) MIME-Version: 1.0 References: <20180830143904.3168-1-yu-cheng.yu@intel.com> <20180830143904.3168-7-yu-cheng.yu@intel.com> In-Reply-To: <20180830143904.3168-7-yu-cheng.yu@intel.com> From: Jann Horn Date: Fri, 31 Aug 2018 17:01:42 +0200 Message-ID: Subject: Re: [RFC PATCH v3 06/24] x86/cet: Control protection exception handler To: yu-cheng.yu@intel.com Cc: "the arch/x86 maintainers" , "H . Peter Anvin" , Thomas Gleixner , Ingo Molnar , kernel list , linux-doc@vger.kernel.org, Linux-MM , linux-arch , Linux API , Arnd Bergmann , Andy Lutomirski , Balbir Singh , Cyrill Gorcunov , Dave Hansen , Florian Weimer , hjl.tools@gmail.com, Jonathan Corbet , keescook@chromiun.org, Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , ravi.v.shankar@intel.com, vedvyas.shanbhogue@intel.com Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 30, 2018 at 4:43 PM Yu-cheng Yu wrote: > > A control protection exception is triggered when a control flow transfer > attempt violated shadow stack or indirect branch tracking constraints. > For example, the return address for a RET instruction differs from the > safe copy on the shadow stack; or a JMP instruction arrives at a non- > ENDBR instruction. > > The control protection exception handler works in a similar way as the > general protection fault handler. Is there a reason why all the code in this patch isn't #ifdef'ed away on builds that don't support CET? It looks like the CET handler is hooked up to the IDT conditionally, but the handler code is always built? > Signed-off-by: Yu-cheng Yu > --- > arch/x86/entry/entry_64.S | 2 +- > arch/x86/include/asm/traps.h | 3 ++ > arch/x86/kernel/idt.c | 4 +++ > arch/x86/kernel/traps.c | 58 ++++++++++++++++++++++++++++++++++++ > 4 files changed, 66 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S > index 957dfb693ecc..5f4914e988df 100644 > --- a/arch/x86/entry/entry_64.S > +++ b/arch/x86/entry/entry_64.S > @@ -1000,7 +1000,7 @@ idtentry spurious_interrupt_bug do_spurious_interrupt_bug has_error_code=0 > idtentry coprocessor_error do_coprocessor_error has_error_code=0 > idtentry alignment_check do_alignment_check has_error_code=1 > idtentry simd_coprocessor_error do_simd_coprocessor_error has_error_code=0 > - > +idtentry control_protection do_control_protection has_error_code=1 > > /* > * Reload gs selector with exception handling > diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h > index 3de69330e6c5..5196050ff3d5 100644 > --- a/arch/x86/include/asm/traps.h > +++ b/arch/x86/include/asm/traps.h > @@ -26,6 +26,7 @@ asmlinkage void invalid_TSS(void); > asmlinkage void segment_not_present(void); > asmlinkage void stack_segment(void); > asmlinkage void general_protection(void); > +asmlinkage void control_protection(void); > asmlinkage void page_fault(void); > asmlinkage void async_page_fault(void); > asmlinkage void spurious_interrupt_bug(void); > @@ -77,6 +78,7 @@ dotraplinkage void do_stack_segment(struct pt_regs *, long); > dotraplinkage void do_double_fault(struct pt_regs *, long); > #endif > dotraplinkage void do_general_protection(struct pt_regs *, long); > +dotraplinkage void do_control_protection(struct pt_regs *, long); > dotraplinkage void do_page_fault(struct pt_regs *, unsigned long); > dotraplinkage void do_spurious_interrupt_bug(struct pt_regs *, long); > dotraplinkage void do_coprocessor_error(struct pt_regs *, long); > @@ -142,6 +144,7 @@ enum { > X86_TRAP_AC, /* 17, Alignment Check */ > X86_TRAP_MC, /* 18, Machine Check */ > X86_TRAP_XF, /* 19, SIMD Floating-Point Exception */ > + X86_TRAP_CP = 21, /* 21 Control Protection Fault */ > X86_TRAP_IRET = 32, /* 32, IRET Exception */ > }; > > diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c > index 01adea278a71..2d02fdd599a2 100644 > --- a/arch/x86/kernel/idt.c > +++ b/arch/x86/kernel/idt.c > @@ -104,6 +104,10 @@ static const __initconst struct idt_data def_idts[] = { > #elif defined(CONFIG_X86_32) > SYSG(IA32_SYSCALL_VECTOR, entry_INT80_32), > #endif > + > +#ifdef CONFIG_X86_INTEL_CET > + INTG(X86_TRAP_CP, control_protection), > +#endif > }; > > /* > diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c > index e6db475164ed..21a713b96148 100644 > --- a/arch/x86/kernel/traps.c > +++ b/arch/x86/kernel/traps.c > @@ -578,6 +578,64 @@ do_general_protection(struct pt_regs *regs, long error_code) > } > NOKPROBE_SYMBOL(do_general_protection); > > +static const char *control_protection_err[] = > +{ > + "unknown", > + "near-ret", > + "far-ret/iret", > + "endbranch", > + "rstorssp", > + "setssbsy", > +}; > + > +/* > + * When a control protection exception occurs, send a signal > + * to the responsible application. Currently, control > + * protection is only enabled for the user mode. This > + * exception should not come from the kernel mode. > + */ > +dotraplinkage void > +do_control_protection(struct pt_regs *regs, long error_code) > +{ > + struct task_struct *tsk; > + > + RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); > + if (notify_die(DIE_TRAP, "control protection fault", regs, > + error_code, X86_TRAP_CP, SIGSEGV) == NOTIFY_STOP) > + return; > + cond_local_irq_enable(regs); > + > + if (!user_mode(regs)) > + die("kernel control protection fault", regs, error_code); > + > + if (!static_cpu_has(X86_FEATURE_SHSTK) && > + !static_cpu_has(X86_FEATURE_IBT)) > + WARN_ONCE(1, "CET is disabled but got control " > + "protection fault\n"); > + > + tsk = current; > + tsk->thread.error_code = error_code; > + tsk->thread.trap_nr = X86_TRAP_CP; > + > + if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) && > + printk_ratelimit()) { > + unsigned int max_err; > + > + max_err = ARRAY_SIZE(control_protection_err) - 1; > + if ((error_code < 0) || (error_code > max_err)) > + error_code = 0; > + pr_info("%s[%d] control protection ip:%lx sp:%lx error:%lx(%s)", > + tsk->comm, task_pid_nr(tsk), > + regs->ip, regs->sp, error_code, > + control_protection_err[error_code]); > + print_vma_addr(" in ", regs->ip); Shouldn't this be using KERN_CONT, like other callers of print_vma_addr(), to get the desired output? > + pr_cont("\n"); > + } > + > + force_sig_info(SIGSEGV, SEND_SIG_PRIV, tsk); From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jann Horn Subject: Re: [RFC PATCH v3 06/24] x86/cet: Control protection exception handler Date: Fri, 31 Aug 2018 17:01:42 +0200 Message-ID: References: <20180830143904.3168-1-yu-cheng.yu@intel.com> <20180830143904.3168-7-yu-cheng.yu@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: <20180830143904.3168-7-yu-cheng.yu@intel.com> Sender: linux-kernel-owner@vger.kernel.org To: yu-cheng.yu@intel.com Cc: the arch/x86 maintainers , "H . Peter Anvin" , Thomas Gleixner , Ingo Molnar , kernel list , linux-doc@vger.kernel.org, Linux-MM , linux-arch , Linux API , Arnd Bergmann , Andy Lutomirski , Balbir Singh , Cyrill Gorcunov , Dave Hansen , Florian Weimer , hjl.tools@gmail.com, Jonathan Corbet , keescook@chromiun.org, Mike Kravetz , Nadav Amit , Oleg Nesterov Pavel Machek List-Id: linux-api@vger.kernel.org On Thu, Aug 30, 2018 at 4:43 PM Yu-cheng Yu wrote: > > A control protection exception is triggered when a control flow transfer > attempt violated shadow stack or indirect branch tracking constraints. > For example, the return address for a RET instruction differs from the > safe copy on the shadow stack; or a JMP instruction arrives at a non- > ENDBR instruction. > > The control protection exception handler works in a similar way as the > general protection fault handler. Is there a reason why all the code in this patch isn't #ifdef'ed away on builds that don't support CET? It looks like the CET handler is hooked up to the IDT conditionally, but the handler code is always built? > Signed-off-by: Yu-cheng Yu > --- > arch/x86/entry/entry_64.S | 2 +- > arch/x86/include/asm/traps.h | 3 ++ > arch/x86/kernel/idt.c | 4 +++ > arch/x86/kernel/traps.c | 58 ++++++++++++++++++++++++++++++++++++ > 4 files changed, 66 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S > index 957dfb693ecc..5f4914e988df 100644 > --- a/arch/x86/entry/entry_64.S > +++ b/arch/x86/entry/entry_64.S > @@ -1000,7 +1000,7 @@ idtentry spurious_interrupt_bug do_spurious_interrupt_bug has_error_code=0 > idtentry coprocessor_error do_coprocessor_error has_error_code=0 > idtentry alignment_check do_alignment_check has_error_code=1 > idtentry simd_coprocessor_error do_simd_coprocessor_error has_error_code=0 > - > +idtentry control_protection do_control_protection has_error_code=1 > > /* > * Reload gs selector with exception handling > diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h > index 3de69330e6c5..5196050ff3d5 100644 > --- a/arch/x86/include/asm/traps.h > +++ b/arch/x86/include/asm/traps.h > @@ -26,6 +26,7 @@ asmlinkage void invalid_TSS(void); > asmlinkage void segment_not_present(void); > asmlinkage void stack_segment(void); > asmlinkage void general_protection(void); > +asmlinkage void control_protection(void); > asmlinkage void page_fault(void); > asmlinkage void async_page_fault(void); > asmlinkage void spurious_interrupt_bug(void); > @@ -77,6 +78,7 @@ dotraplinkage void do_stack_segment(struct pt_regs *, long); > dotraplinkage void do_double_fault(struct pt_regs *, long); > #endif > dotraplinkage void do_general_protection(struct pt_regs *, long); > +dotraplinkage void do_control_protection(struct pt_regs *, long); > dotraplinkage void do_page_fault(struct pt_regs *, unsigned long); > dotraplinkage void do_spurious_interrupt_bug(struct pt_regs *, long); > dotraplinkage void do_coprocessor_error(struct pt_regs *, long); > @@ -142,6 +144,7 @@ enum { > X86_TRAP_AC, /* 17, Alignment Check */ > X86_TRAP_MC, /* 18, Machine Check */ > X86_TRAP_XF, /* 19, SIMD Floating-Point Exception */ > + X86_TRAP_CP = 21, /* 21 Control Protection Fault */ > X86_TRAP_IRET = 32, /* 32, IRET Exception */ > }; > > diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c > index 01adea278a71..2d02fdd599a2 100644 > --- a/arch/x86/kernel/idt.c > +++ b/arch/x86/kernel/idt.c > @@ -104,6 +104,10 @@ static const __initconst struct idt_data def_idts[] = { > #elif defined(CONFIG_X86_32) > SYSG(IA32_SYSCALL_VECTOR, entry_INT80_32), > #endif > + > +#ifdef CONFIG_X86_INTEL_CET > + INTG(X86_TRAP_CP, control_protection), > +#endif > }; > > /* > diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c > index e6db475164ed..21a713b96148 100644 > --- a/arch/x86/kernel/traps.c > +++ b/arch/x86/kernel/traps.c > @@ -578,6 +578,64 @@ do_general_protection(struct pt_regs *regs, long error_code) > } > NOKPROBE_SYMBOL(do_general_protection); > > +static const char *control_protection_err[] = > +{ > + "unknown", > + "near-ret", > + "far-ret/iret", > + "endbranch", > + "rstorssp", > + "setssbsy", > +}; > + > +/* > + * When a control protection exception occurs, send a signal > + * to the responsible application. Currently, control > + * protection is only enabled for the user mode. This > + * exception should not come from the kernel mode. > + */ > +dotraplinkage void > +do_control_protection(struct pt_regs *regs, long error_code) > +{ > + struct task_struct *tsk; > + > + RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); > + if (notify_die(DIE_TRAP, "control protection fault", regs, > + error_code, X86_TRAP_CP, SIGSEGV) == NOTIFY_STOP) > + return; > + cond_local_irq_enable(regs); > + > + if (!user_mode(regs)) > + die("kernel control protection fault", regs, error_code); > + > + if (!static_cpu_has(X86_FEATURE_SHSTK) && > + !static_cpu_has(X86_FEATURE_IBT)) > + WARN_ONCE(1, "CET is disabled but got control " > + "protection fault\n"); > + > + tsk = current; > + tsk->thread.error_code = error_code; > + tsk->thread.trap_nr = X86_TRAP_CP; > + > + if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) && > + printk_ratelimit()) { > + unsigned int max_err; > + > + max_err = ARRAY_SIZE(control_protection_err) - 1; > + if ((error_code < 0) || (error_code > max_err)) > + error_code = 0; > + pr_info("%s[%d] control protection ip:%lx sp:%lx error:%lx(%s)", > + tsk->comm, task_pid_nr(tsk), > + regs->ip, regs->sp, error_code, > + control_protection_err[error_code]); > + print_vma_addr(" in ", regs->ip); Shouldn't this be using KERN_CONT, like other callers of print_vma_addr(), to get the desired output? > + pr_cont("\n"); > + } > + > + force_sig_info(SIGSEGV, SEND_SIG_PRIV, tsk);