Re: [PATCH v21 06/26] x86/cet: Add control-protection fault handler

On 2/24/2021 8:13 AM, Borislav Petkov wrote:

On Wed, Feb 17, 2021 at 02:27:10PM -0800, Yu-cheng Yu wrote:

quoted

+/*
+ * When a control protection exception occurs, send a signal to the responsible
+ * application.  Currently, control protection is only enabled for user mode.
+ * This exception should not come from kernel mode.
+ */
+DEFINE_IDTENTRY_ERRORCODE(exc_control_protection)
+{
+	static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
+				      DEFAULT_RATELIMIT_BURST);

[...]

quoted

+
+		rdmsrl(MSR_IA32_PL3_SSP, ssp);
+		pr_emerg("%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[err]);
+		print_vma_addr(KERN_CONT " in ", regs->ip);
+		pr_cont("\n");
+	}
+
+	force_sig_fault(SIGSEGV, SEGV_CPERR,
+			(void __user *)uprobe_get_trap_addr(regs));

Why is this calling an uprobes function?

I will change it to error_get_trap_addr().

Also, do not break that line even if it is longer than 80.

quoted

+	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

I still don't see the patch adding this to the manpage of sigaction(2).

There's a git repo there: https://www.kernel.org/doc/man-pages/

and I'm pretty sure Michael takes patches.

I will send a patch.

--
Yu-cheng