5 files changed, 88 insertions, 24 deletions

diff --git a/arch/x86/kernel/cet.c b/arch/x86/kernel/cet.c
index 7ad22b705b64..cc10d8be9d74 100644
--- a/arch/x86/kernel/cet.c
+++ b/arch/x86/kernel/cet.c
@@ -4,10 +4,6 @@
 #include <asm/bugs.h>
 #include <asm/traps.h>
 
-static __ro_after_init bool ibt_fatal = true;
-
-extern void ibt_selftest_ip(void); /* code label defined in asm below */
-
 enum cp_error_code {
 	CP_EC        = (1 << 15) - 1,
 
@@ -20,15 +16,80 @@ enum cp_error_code {
 	CP_ENCL	     = 1 << 15,
 };
 
-DEFINE_IDTENTRY_ERRORCODE(exc_control_protection)
+static const char cp_err[][10] = {
+	[0] = "unknown",
+	[1] = "near ret",
+	[2] = "far/iret",
+	[3] = "endbranch",
+	[4] = "rstorssp",
+	[5] = "setssbsy",
+};
+
+static const char *cp_err_string(unsigned long error_code)
+{
+	unsigned int cpec = error_code & CP_EC;
+
+	if (cpec >= ARRAY_SIZE(cp_err))
+		cpec = 0;
+	return cp_err[cpec];
+}
+
+static void do_unexpected_cp(struct pt_regs *regs, unsigned long error_code)
+{
+	WARN_ONCE(1, "Unexpected %s #CP, error_code: %s\n",
+		  user_mode(regs) ? "user mode" : "kernel mode",
+		  cp_err_string(error_code));
+}
+
+static DEFINE_RATELIMIT_STATE(cpf_rate, DEFAULT_RATELIMIT_INTERVAL,
+			      DEFAULT_RATELIMIT_BURST);
+
+static void do_user_cp_fault(struct pt_regs *regs, unsigned long error_code)
 {
-	if (!cpu_feature_enabled(X86_FEATURE_IBT)) {
-		pr_err("Unexpected #CP\n");
-		BUG();
+	struct task_struct *tsk;
+	unsigned long ssp;
+
+	/*
+	 * An exception was just taken from userspace. Since interrupts are disabled
+	 * here, no scheduling should have messed with the registers yet and they
+	 * will be whatever is live in userspace. So read the SSP before enabling
+	 * interrupts so locking the fpregs to do it later is not required.
+	 */
+	rdmsrl(MSR_IA32_PL3_SSP, ssp);
+
+	cond_local_irq_enable(regs);
+
+	tsk = current;
+	tsk->thread.error_code = error_code;
+	tsk->thread.trap_nr = X86_TRAP_CP;
+
+	/* Ratelimit to prevent log spamming. */
+	if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) &&
+	    __ratelimit(&cpf_rate)) {
+		pr_emerg("%s[%d] control protection ip:%lx sp:%lx ssp:%lx error:%lx(%s)%s",
+			 tsk->comm, task_pid_nr(tsk),
+			 regs->ip, regs->sp, ssp, error_code,
+			 cp_err_string(error_code),
+			 error_code & CP_ENCL ? " in enclave" : "");
+		print_vma_addr(KERN_CONT " in ", regs->ip);
+		pr_cont("\n");
 	}
 
-	if (WARN_ON_ONCE(user_mode(regs) || (error_code & CP_EC) != CP_ENDBR))
+	force_sig_fault(SIGSEGV, SEGV_CPERR, (void __user *)0);
+	cond_local_irq_disable(regs);
+}
+
+static __ro_after_init bool ibt_fatal = true;
+
+/* code label defined in asm below */
+extern void ibt_selftest_ip(void);
+
+static void do_kernel_cp_fault(struct pt_regs *regs, unsigned long error_code)
+{
+	if ((error_code & CP_EC) != CP_ENDBR) {
+		do_unexpected_cp(regs, error_code);
 		return;
+	}
 
 	if (unlikely(regs->ip == (unsigned long)&ibt_selftest_ip)) {
 		regs->ax = 0;
@@ -74,3 +135,18 @@ static int __init ibt_setup(char *str)
 }
 
 __setup("ibt=", ibt_setup);
+
+DEFINE_IDTENTRY_ERRORCODE(exc_control_protection)
+{
+	if (user_mode(regs)) {
+		if (cpu_feature_enabled(X86_FEATURE_USER_SHSTK))
+			do_user_cp_fault(regs, error_code);
+		else
+			do_unexpected_cp(regs, error_code);
+	} else {
+		if (cpu_feature_enabled(X86_FEATURE_IBT))
+			do_kernel_cp_fault(regs, error_code);
+		else
+			do_unexpected_cp(regs, error_code);
+	}
+}
diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c
index a58c6bc1cd68..5074b8420359 100644
--- a/arch/x86/kernel/idt.c
+++ b/arch/x86/kernel/idt.c
@@ -107,7 +107,7 @@ static const __initconst struct idt_data def_idts[] = {
 	ISTG(X86_TRAP_MC,		asm_exc_machine_check, IST_INDEX_MCE),
 #endif
 
-#ifdef CONFIG_X86_KERNEL_IBT
+#ifdef CONFIG_X86_CET
 	INTG(X86_TRAP_CP,		asm_exc_control_protection),
 #endif
 
diff --git a/arch/x86/kernel/signal_32.c b/arch/x86/kernel/signal_32.c
index 9027fc088f97..c12624bc82a3 100644
--- a/arch/x86/kernel/signal_32.c
+++ b/arch/x86/kernel/signal_32.c
@@ -402,7 +402,7 @@ Efault:
 */
 static_assert(NSIGILL  == 11);
 static_assert(NSIGFPE  == 15);
-static_assert(NSIGSEGV == 9);
+static_assert(NSIGSEGV == 10);
 static_assert(NSIGBUS  == 5);
 static_assert(NSIGTRAP == 6);
 static_assert(NSIGCHLD == 6);
diff --git a/arch/x86/kernel/signal_64.c b/arch/x86/kernel/signal_64.c
index 13a1e6083837..0e808c72bf7e 100644
--- a/arch/x86/kernel/signal_64.c
+++ b/arch/x86/kernel/signal_64.c
@@ -403,7 +403,7 @@ void sigaction_compat_abi(struct k_sigaction *act, struct k_sigaction *oact)
 */
 static_assert(NSIGILL  == 11);
 static_assert(NSIGFPE  == 15);
-static_assert(NSIGSEGV == 9);
+static_assert(NSIGSEGV == 10);
 static_assert(NSIGBUS  == 5);
 static_assert(NSIGTRAP == 6);
 static_assert(NSIGCHLD == 6);
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 6f666dfa97de..f358350624b2 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -77,18 +77,6 @@
 
 DECLARE_BITMAP(system_vectors, NR_VECTORS);
 
-static inline void cond_local_irq_enable(struct pt_regs *regs)
-{
-	if (regs->flags & X86_EFLAGS_IF)
-		local_irq_enable();
-}
-
-static inline void cond_local_irq_disable(struct pt_regs *regs)
-{
-	if (regs->flags & X86_EFLAGS_IF)
-		local_irq_disable();
-}
-
 __always_inline int is_valid_bugaddr(unsigned long addr)
 {
 	if (addr < TASK_SIZE_MAX)