| Message ID | 20201229213053.16395-7-yu-cheng.yu@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Control-flow Enforcement: Shadow Stack | expand |
On Tue, Dec 29, 2020 at 01:30:33PM -0800, Yu-cheng Yu wrote: > @@ -606,6 +606,65 @@ DEFINE_IDTENTRY_ERRORCODE(exc_general_protection) > cond_local_irq_disable(regs); > } > > +#ifdef CONFIG_X86_CET_USER > +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. > + */ There's no "the user mode" or "the kernel mode" - just "user mode" or "kernel mode". > +DEFINE_IDTENTRY_ERRORCODE(exc_control_protection) > +{ > + struct task_struct *tsk; > + > + if (!user_mode(regs)) { > + if (notify_die(DIE_TRAP, "control protection fault", regs, > + error_code, X86_TRAP_CP, SIGSEGV) == NOTIFY_STOP) > + return; > + die("Upexpected/unsupported kernel control protection fault", regs, error_code); Isn't the machine supposed to panic() here and do no further progress? > + } > + > + cond_local_irq_enable(regs); > + > + if (!boot_cpu_has(X86_FEATURE_CET)) > + WARN_ONCE(1, "Control protection fault with CET support disabled\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()) { WARNING: Prefer printk_ratelimited or pr_<level>_ratelimited to printk_ratelimit #136: FILE: arch/x86/kernel/traps.c:645: + printk_ratelimit()) { Still not using checkpatch? > + 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)", If anything, all this stuff should be pr_emerg(). > + 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)); > + cond_local_irq_disable(regs); > +} > +#endif > + > static bool do_int3(struct pt_regs *regs) > { > int res; > diff --git a/include/uapi/asm-generic/siginfo.h b/include/uapi/asm-generic/siginfo.h > index d2597000407a..1c2ea91284a0 100644 > --- a/include/uapi/asm-generic/siginfo.h > +++ b/include/uapi/asm-generic/siginfo.h > @@ -231,7 +231,8 @@ typedef struct siginfo { > #define SEGV_ADIPERR 7 /* Precise MCD exception */ > #define SEGV_MTEAERR 8 /* Asynchronous ARM MTE error */ > #define SEGV_MTESERR 9 /* Synchronous ARM MTE exception */ > -#define NSIGSEGV 9 > +#define SEGV_CPERR 10 /* Control protection fault */ > +#define NSIGSEGV 10 This looks like it needs documentation in this manpage: https://www.man7.org/linux/man-pages/man2/sigaction.2.html + Michael.
On 1/19/2021 4:04 AM, Borislav Petkov wrote: > On Tue, Dec 29, 2020 at 01:30:33PM -0800, Yu-cheng Yu wrote: [...] >> +DEFINE_IDTENTRY_ERRORCODE(exc_control_protection) >> +{ >> + struct task_struct *tsk; >> + >> + if (!user_mode(regs)) { >> + if (notify_die(DIE_TRAP, "control protection fault", regs, >> + error_code, X86_TRAP_CP, SIGSEGV) == NOTIFY_STOP) >> + return; >> + die("Upexpected/unsupported kernel control protection fault", regs, error_code); > > Isn't the machine supposed to panic() here and do no further progress? Ok, make it panic(). >> + } >> + >> + cond_local_irq_enable(regs); >> + >> + if (!boot_cpu_has(X86_FEATURE_CET)) >> + WARN_ONCE(1, "Control protection fault with CET support disabled\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()) { > > WARNING: Prefer printk_ratelimited or pr_<level>_ratelimited to printk_ratelimit > #136: FILE: arch/x86/kernel/traps.c:645: > + printk_ratelimit()) { > > Still not using checkpatch? Most places in arch/x86 still use printk_ratelimit(). I should have trusted checkpatch. I will fix it. >> + 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)", > > If anything, all this stuff should be pr_emerg(). I will fix it. -- Yu-cheng
diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h index 247a60a47331..244dee0e092a 100644 --- a/arch/x86/include/asm/idtentry.h +++ b/arch/x86/include/asm/idtentry.h @@ -574,6 +574,10 @@ DECLARE_IDTENTRY_ERRORCODE(X86_TRAP_SS, exc_stack_segment); DECLARE_IDTENTRY_ERRORCODE(X86_TRAP_GP, exc_general_protection); DECLARE_IDTENTRY_ERRORCODE(X86_TRAP_AC, exc_alignment_check); +#ifdef CONFIG_X86_CET_USER +DECLARE_IDTENTRY_ERRORCODE(X86_TRAP_CP, exc_control_protection); +#endif + /* Raw exception entries which need extra work */ DECLARE_IDTENTRY_RAW(X86_TRAP_UD, exc_invalid_op); DECLARE_IDTENTRY_RAW(X86_TRAP_BP, exc_int3); diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c index ee1a283f8e96..463dcae55c3f 100644 --- a/arch/x86/kernel/idt.c +++ b/arch/x86/kernel/idt.c @@ -105,6 +105,10 @@ static const __initconst struct idt_data def_idts[] = { #elif defined(CONFIG_X86_32) SYSG(IA32_SYSCALL_VECTOR, entry_INT80_32), #endif + +#ifdef CONFIG_X86_CET_USER + INTG(X86_TRAP_CP, asm_exc_control_protection), +#endif }; /* diff --git a/arch/x86/kernel/signal_compat.c b/arch/x86/kernel/signal_compat.c index a5330ff498f0..dd92490b1e7f 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 != 9); + BUILD_BUG_ON(NSIGSEGV != 10); 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 7f5aec758f0e..b0a3e05f9950 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -606,6 +606,65 @@ DEFINE_IDTENTRY_ERRORCODE(exc_general_protection) cond_local_irq_disable(regs); } +#ifdef CONFIG_X86_CET_USER +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. + */ +DEFINE_IDTENTRY_ERRORCODE(exc_control_protection) +{ + struct task_struct *tsk; + + if (!user_mode(regs)) { + if (notify_die(DIE_TRAP, "control protection fault", regs, + error_code, X86_TRAP_CP, SIGSEGV) == NOTIFY_STOP) + return; + die("Upexpected/unsupported kernel control protection fault", regs, error_code); + } + + cond_local_irq_enable(regs); + + if (!boot_cpu_has(X86_FEATURE_CET)) + WARN_ONCE(1, "Control protection fault with CET support disabled\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)); + cond_local_irq_disable(regs); +} +#endif + static bool do_int3(struct pt_regs *regs) { int res; diff --git a/include/uapi/asm-generic/siginfo.h b/include/uapi/asm-generic/siginfo.h index d2597000407a..1c2ea91284a0 100644 --- a/include/uapi/asm-generic/siginfo.h +++ b/include/uapi/asm-generic/siginfo.h @@ -231,7 +231,8 @@ typedef struct siginfo { #define SEGV_ADIPERR 7 /* Precise MCD exception */ #define SEGV_MTEAERR 8 /* Asynchronous ARM MTE error */ #define SEGV_MTESERR 9 /* Synchronous ARM MTE exception */ -#define NSIGSEGV 9 +#define SEGV_CPERR 10 /* Control protection fault */ +#define NSIGSEGV 10 /* * 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. Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com> --- arch/x86/include/asm/idtentry.h | 4 ++ 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 +- 5 files changed, 70 insertions(+), 2 deletions(-)