2 files changed, 38 insertions, 0 deletions
diff --git a/src/syscall/exec_unix.go b/src/syscall/exec_unix.go
index b3798b6e04..0345af44f9 100644
--- a/src/syscall/exec_unix.go
+++ b/src/syscall/exec_unix.go
@@ -9,6 +9,7 @@
 package syscall
 
 import (
+	errorspkg "errors"
 	"internal/bytealg"
 	"runtime"
 	"sync"
@@ -187,6 +188,15 @@ func forkExec(argv0 string, argv []string, attr *ProcAttr) (pid int, err error)
 		}
 	}
 
+	// Both Setctty and Foreground use the Ctty field,
+	// but they give it slightly different meanings.
+	if sys.Setctty && sys.Foreground {
+		return 0, errorspkg.New("both Setctty and Foreground set in SysProcAttr")
+	}
+	if sys.Setctty && sys.Ctty >= len(attr.Files) {
+		return 0, errorspkg.New("Setctty set but Ctty not valid in child")
+	}
+
 	// Acquire the fork lock so that no other threads
 	// create new fds that are not yet close-on-exec
 	// before we fork.
diff --git a/src/syscall/exec_unix_test.go b/src/syscall/exec_unix_test.go
index 33614f5221..4eb3c5c6c8 100644
--- a/src/syscall/exec_unix_test.go
+++ b/src/syscall/exec_unix_test.go
@@ -213,3 +213,31 @@ func TestForeground(t *testing.T) {
 
 	signal.Reset()
 }
+
+// Test a couple of cases that SysProcAttr can't handle. Issue 29458.
+func TestInvalidExec(t *testing.T) {
+	t.Parallel()
+	t.Run("SetCtty-Foreground", func(t *testing.T) {
+		t.Parallel()
+		cmd := create(t)
+		cmd.proc.SysProcAttr = &syscall.SysProcAttr{
+			Setctty:    true,
+			Foreground: true,
+			Ctty:       0,
+		}
+		if err := cmd.proc.Start(); err == nil {
+			t.Error("expected error setting both SetCtty and Foreground")
+		}
+	})
+	t.Run("invalid-Ctty", func(t *testing.T) {
+		t.Parallel()
+		cmd := create(t)
+		cmd.proc.SysProcAttr = &syscall.SysProcAttr{
+			Setctty: true,
+			Ctty:    3,
+		}
+		if err := cmd.proc.Start(); err == nil {
+			t.Error("expected error with invalid Ctty value")
+		}
+	})
+}