Re: [PATCH v17 06/26] x86/cet: Add control-protection fault handler
From: Borislav Petkov <bp@alien8.de>
Date: 2021-01-19 12:13:39
Also in:
linux-arch, linux-doc, linux-mm, lkml
On Tue, Dec 29, 2020 at 01:30:33PM -0800, Yu-cheng Yu wrote:
quoted hunk ↗ jump to hunk
@@ -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().
quoted hunk ↗ jump to hunk
+ 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. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette