diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index f51cab3e983d..b001ba811cab 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -234,10 +234,11 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
 	     void __user **fpstate)
 {
 	/* Default to using normal stack */
+	bool nested_altstack = on_sig_stack(regs->sp);
+	bool entering_altstack = false;
 	unsigned long math_size = 0;
 	unsigned long sp = regs->sp;
 	unsigned long buf_fx = 0;
-	int onsigstack = on_sig_stack(sp);
 	int ret;
 
 	/* redzone */
@@ -246,15 +247,23 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
 
 	/* This is the X/Open sanctioned signal stack switching.  */
 	if (ka->sa.sa_flags & SA_ONSTACK) {
-		if (sas_ss_flags(sp) == 0)
+		/*
+		 * This checks nested_altstack via sas_ss_flags(). Sensible
+		 * programs use SS_AUTODISARM, which disables that check, and
+		 * programs that don't use SS_AUTODISARM get compatible.
+		 */
+		if (sas_ss_flags(sp) == 0) {
 			sp = current->sas_ss_sp + current->sas_ss_size;
+			entering_altstack = true;
+		}
 	} else if (IS_ENABLED(CONFIG_X86_32) &&
-		   !onsigstack &&
+		   !nested_altstack &&
 		   regs->ss != __USER_DS &&
 		   !(ka->sa.sa_flags & SA_RESTORER) &&
 		   ka->sa.sa_restorer) {
 		/* This is the legacy signal stack switching. */
 		sp = (unsigned long) ka->sa.sa_restorer;
+		entering_altstack = true;
 	}
 
 	sp = fpu__alloc_mathframe(sp, IS_ENABLED(CONFIG_X86_32),
@@ -267,8 +276,15 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
 	 * If we are on the alternate signal stack and would overflow it, don't.
 	 * Return an always-bogus address instead so we will die with SIGSEGV.
 	 */
-	if (onsigstack && !likely(on_sig_stack(sp)))
+	if (unlikely((nested_altstack || entering_altstack) &&
+		     !__on_sig_stack(sp))) {
+
+		if (show_unhandled_signals && printk_ratelimit())
+			pr_info("%s[%d] overflowed sigaltstack\n",
+				current->comm, task_pid_nr(current));
+
 		return (void __user *)-1L;
+	}
 
 	/* save i387 and extended state */
 	ret = copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size);
diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h
index 4b6a8234d7fc..657640015b33 100644
--- a/include/linux/sched/signal.h
+++ b/include/linux/sched/signal.h
@@ -525,6 +525,17 @@ static inline int kill_cad_pid(int sig, int priv)
 #define SEND_SIG_NOINFO ((struct kernel_siginfo *) 0)
 #define SEND_SIG_PRIV	((struct kernel_siginfo *) 1)
 
+static inline int __on_sig_stack(unsigned long sp)
+{
+#ifdef CONFIG_STACK_GROWSUP
+	return sp >= current->sas_ss_sp &&
+		sp - current->sas_ss_sp < current->sas_ss_size;
+#else
+	return sp > current->sas_ss_sp &&
+		sp - current->sas_ss_sp <= current->sas_ss_size;
+#endif
+}
+
 /*
  * True if we are on the alternate signal stack.
  */
@@ -542,13 +553,7 @@ static inline int on_sig_stack(unsigned long sp)
 	if (current->sas_ss_flags & SS_AUTODISARM)
 		return 0;
 
-#ifdef CONFIG_STACK_GROWSUP
-	return sp >= current->sas_ss_sp &&
-		sp - current->sas_ss_sp < current->sas_ss_size;
-#else
-	return sp > current->sas_ss_sp &&
-		sp - current->sas_ss_sp <= current->sas_ss_size;
-#endif
+	return __on_sig_stack(sp);
 }
 
 static inline int sas_ss_flags(unsigned long sp)