| Message ID | 20200205181935.3712-5-yu-cheng.yu@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Control-flow Enforcement: Shadow Stack | expand |
On Wed, Feb 05, 2020 at 10:19:12AM -0800, Yu-cheng Yu wrote: > A control-protection fault is triggered when a control-flow transfer > attempt violates Shadow Stack or Indirect Branch Tracking constraints. > For example, the return address for a RET instruction differs from the copy > on the Shadow Stack; or an indirect JMP instruction, without the NOTRACK > prefix, arrives at a non-ENDBR opcode. > > The control-protection fault handler works in a similar way as the general > protection fault handler. It provides the si_code SEGV_CPERR to the signal > handler. > > v9: > - Add Shadow Stack pointer to the fault printout. > > Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com> Reviewed-by: Kees Cook <keescook@chromium.org> -Kees > --- > arch/x86/entry/entry_64.S | 2 +- > arch/x86/include/asm/traps.h | 3 ++ > arch/x86/kernel/idt.c | 4 ++ > arch/x86/kernel/signal_compat.c | 2 +- > arch/x86/kernel/traps.c | 59 ++++++++++++++++++++++++++++++ > include/uapi/asm-generic/siginfo.h | 3 +- > 6 files changed, 70 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S > index 76942cbd95a1..6ca77312d008 100644 > --- a/arch/x86/entry/entry_64.S > +++ b/arch/x86/entry/entry_64.S > @@ -1034,7 +1034,7 @@ 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 ffa0dc8a535e..7ac26bbd0bef 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); > @@ -84,6 +85,7 @@ struct bad_iret_stack *fixup_bad_iret(struct bad_iret_stack *s); > void __init trap_init(void); > #endif > dotraplinkage void do_general_protection(struct pt_regs *regs, long error_code); > +dotraplinkage void do_control_protection(struct pt_regs *regs, long error_code); > dotraplinkage void do_page_fault(struct pt_regs *regs, unsigned long error_code, unsigned long address); > dotraplinkage void do_spurious_interrupt_bug(struct pt_regs *regs, long error_code); > dotraplinkage void do_coprocessor_error(struct pt_regs *regs, long error_code); > @@ -154,6 +156,7 @@ 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 87ef69a72c52..8ed406f469e7 100644 > --- a/arch/x86/kernel/idt.c > +++ b/arch/x86/kernel/idt.c > @@ -102,6 +102,10 @@ static const __initconst struct idt_data def_idts[] = { > #elif defined(CONFIG_X86_32) > SYSG(IA32_SYSCALL_VECTOR, entry_INT80_32), > #endif > + > +#ifdef CONFIG_X86_64 > + INTG(X86_TRAP_CP, control_protection), > +#endif > }; > > /* > diff --git a/arch/x86/kernel/signal_compat.c b/arch/x86/kernel/signal_compat.c > index 9ccbf0576cd0..c572a3de1037 100644 > --- a/arch/x86/kernel/signal_compat.c > +++ b/arch/x86/kernel/signal_compat.c > @@ -27,7 +27,7 @@ static inline void signal_compat_build_tests(void) > */ > BUILD_BUG_ON(NSIGILL != 11); > BUILD_BUG_ON(NSIGFPE != 15); > - BUILD_BUG_ON(NSIGSEGV != 7); > + BUILD_BUG_ON(NSIGSEGV != 8); > BUILD_BUG_ON(NSIGBUS != 5); > BUILD_BUG_ON(NSIGTRAP != 5); > BUILD_BUG_ON(NSIGCHLD != 6); > diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c > index 05da6b5b167b..99c83ee522ed 100644 > --- a/arch/x86/kernel/traps.c > +++ b/arch/x86/kernel/traps.c > @@ -570,6 +570,65 @@ do_general_protection(struct pt_regs *regs, long error_code) > } > NOKPROBE_SYMBOL(do_general_protection); > > +static const char * const 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; > + unsigned long ssp; > + > + max_err = ARRAY_SIZE(control_protection_err) - 1; > + if ((error_code < 0) || (error_code > max_err)) > + error_code = 0; > + rdmsrl(MSR_IA32_PL3_SSP, ssp); > + pr_info("%s[%d] control protection ip:%lx sp:%lx ssp:%lx error:%lx(%s)", > + tsk->comm, task_pid_nr(tsk), > + regs->ip, regs->sp, ssp, error_code, > + control_protection_err[error_code]); > + print_vma_addr(KERN_CONT " in ", regs->ip); > + pr_cont("\n"); > + } > + > + force_sig_fault(SIGSEGV, SEGV_CPERR, > + (void __user *)uprobe_get_trap_addr(regs)); > +} > +NOKPROBE_SYMBOL(do_control_protection); > + > dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code) > { > #ifdef CONFIG_DYNAMIC_FTRACE > diff --git a/include/uapi/asm-generic/siginfo.h b/include/uapi/asm-generic/siginfo.h > index cb3d6c267181..693071dbe641 100644 > --- a/include/uapi/asm-generic/siginfo.h > +++ b/include/uapi/asm-generic/siginfo.h > @@ -229,7 +229,8 @@ typedef struct siginfo { > #define SEGV_ACCADI 5 /* ADI not enabled for mapped object */ > #define SEGV_ADIDERR 6 /* Disrupting MCD error */ > #define SEGV_ADIPERR 7 /* Precise MCD exception */ > -#define NSIGSEGV 7 > +#define SEGV_CPERR 8 > +#define NSIGSEGV 8 > > /* > * SIGBUS si_codes > -- > 2.21.0 >
On 2/5/20 10:19 AM, Yu-cheng Yu wrote: > diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c > index 87ef69a72c52..8ed406f469e7 100644 > --- a/arch/x86/kernel/idt.c > +++ b/arch/x86/kernel/idt.c > @@ -102,6 +102,10 @@ static const __initconst struct idt_data def_idts[] = { > #elif defined(CONFIG_X86_32) > SYSG(IA32_SYSCALL_VECTOR, entry_INT80_32), > #endif > + > +#ifdef CONFIG_X86_64 > + INTG(X86_TRAP_CP, control_protection), > +#endif > }; This patch in particular appears to have all of its code unconditionally compiled in. That's in contrast to things that have Kconfig options, like: #ifdef CONFIG_X86_MCE INTG(X86_TRAP_MC, &machine_check), #endif or: #ifdef CONFIG_X86_THERMAL_VECTOR INTG(THERMAL_APIC_VECTOR, thermal_interrupt), #endif Is there a reason this code is always compiled in on 64-bit even when the config option is off?
On Wed, 2020-02-26 at 09:10 -0800, Dave Hansen wrote: > On 2/5/20 10:19 AM, Yu-cheng Yu wrote: > > diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c > > index 87ef69a72c52..8ed406f469e7 100644 > > --- a/arch/x86/kernel/idt.c > > +++ b/arch/x86/kernel/idt.c > > @@ -102,6 +102,10 @@ static const __initconst struct idt_data def_idts[] = { > > #elif defined(CONFIG_X86_32) > > SYSG(IA32_SYSCALL_VECTOR, entry_INT80_32), > > #endif > > + > > +#ifdef CONFIG_X86_64 > > + INTG(X86_TRAP_CP, control_protection), > > +#endif > > }; > > This patch in particular appears to have all of its code unconditionally > compiled in. That's in contrast to things that have Kconfig options, like: > > #ifdef CONFIG_X86_MCE > INTG(X86_TRAP_MC, &machine_check), > #endif > > or: > > #ifdef CONFIG_X86_THERMAL_VECTOR > INTG(THERMAL_APIC_VECTOR, thermal_interrupt), > #endif > > Is there a reason this code is always compiled in on 64-bit even when > the config option is off? I will change it to CONFIG_X86_INTEL_CET. Yu-cheng
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 76942cbd95a1..6ca77312d008 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -1034,7 +1034,7 @@ 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 ffa0dc8a535e..7ac26bbd0bef 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); @@ -84,6 +85,7 @@ struct bad_iret_stack *fixup_bad_iret(struct bad_iret_stack *s); void __init trap_init(void); #endif dotraplinkage void do_general_protection(struct pt_regs *regs, long error_code); +dotraplinkage void do_control_protection(struct pt_regs *regs, long error_code); dotraplinkage void do_page_fault(struct pt_regs *regs, unsigned long error_code, unsigned long address); dotraplinkage void do_spurious_interrupt_bug(struct pt_regs *regs, long error_code); dotraplinkage void do_coprocessor_error(struct pt_regs *regs, long error_code); @@ -154,6 +156,7 @@ 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 87ef69a72c52..8ed406f469e7 100644 --- a/arch/x86/kernel/idt.c +++ b/arch/x86/kernel/idt.c @@ -102,6 +102,10 @@ static const __initconst struct idt_data def_idts[] = { #elif defined(CONFIG_X86_32) SYSG(IA32_SYSCALL_VECTOR, entry_INT80_32), #endif + +#ifdef CONFIG_X86_64 + INTG(X86_TRAP_CP, control_protection), +#endif }; /* diff --git a/arch/x86/kernel/signal_compat.c b/arch/x86/kernel/signal_compat.c index 9ccbf0576cd0..c572a3de1037 100644 --- a/arch/x86/kernel/signal_compat.c +++ b/arch/x86/kernel/signal_compat.c @@ -27,7 +27,7 @@ static inline void signal_compat_build_tests(void) */ BUILD_BUG_ON(NSIGILL != 11); BUILD_BUG_ON(NSIGFPE != 15); - BUILD_BUG_ON(NSIGSEGV != 7); + BUILD_BUG_ON(NSIGSEGV != 8); BUILD_BUG_ON(NSIGBUS != 5); BUILD_BUG_ON(NSIGTRAP != 5); BUILD_BUG_ON(NSIGCHLD != 6); diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 05da6b5b167b..99c83ee522ed 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -570,6 +570,65 @@ do_general_protection(struct pt_regs *regs, long error_code) } NOKPROBE_SYMBOL(do_general_protection); +static const char * const 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; + unsigned long ssp; + + max_err = ARRAY_SIZE(control_protection_err) - 1; + if ((error_code < 0) || (error_code > max_err)) + error_code = 0; + rdmsrl(MSR_IA32_PL3_SSP, ssp); + pr_info("%s[%d] control protection ip:%lx sp:%lx ssp:%lx error:%lx(%s)", + tsk->comm, task_pid_nr(tsk), + regs->ip, regs->sp, ssp, error_code, + control_protection_err[error_code]); + print_vma_addr(KERN_CONT " in ", regs->ip); + pr_cont("\n"); + } + + force_sig_fault(SIGSEGV, SEGV_CPERR, + (void __user *)uprobe_get_trap_addr(regs)); +} +NOKPROBE_SYMBOL(do_control_protection); + dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code) { #ifdef CONFIG_DYNAMIC_FTRACE diff --git a/include/uapi/asm-generic/siginfo.h b/include/uapi/asm-generic/siginfo.h index cb3d6c267181..693071dbe641 100644 --- a/include/uapi/asm-generic/siginfo.h +++ b/include/uapi/asm-generic/siginfo.h @@ -229,7 +229,8 @@ typedef struct siginfo { #define SEGV_ACCADI 5 /* ADI not enabled for mapped object */ #define SEGV_ADIDERR 6 /* Disrupting MCD error */ #define SEGV_ADIPERR 7 /* Precise MCD exception */ -#define NSIGSEGV 7 +#define SEGV_CPERR 8 +#define NSIGSEGV 8 /* * SIGBUS si_codes
A control-protection fault is triggered when a control-flow transfer attempt violates Shadow Stack or Indirect Branch Tracking constraints. For example, the return address for a RET instruction differs from the copy on the Shadow Stack; or an indirect JMP instruction, without the NOTRACK prefix, arrives at a non-ENDBR opcode. The control-protection fault handler works in a similar way as the general protection fault handler. It provides the si_code SEGV_CPERR to the signal handler. v9: - Add Shadow Stack pointer to the fault printout. Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com> --- arch/x86/entry/entry_64.S | 2 +- arch/x86/include/asm/traps.h | 3 ++ arch/x86/kernel/idt.c | 4 ++ arch/x86/kernel/signal_compat.c | 2 +- arch/x86/kernel/traps.c | 59 ++++++++++++++++++++++++++++++ include/uapi/asm-generic/siginfo.h | 3 +- 6 files changed, 70 insertions(+), 3 deletions(-)