net: fix for DialTimeout errors with large timeout

The existing implementation converts the deadline time to an int64,
but does not handle overflow. If the calculated deadline is negative
but the user specified deadline is in the future, then we can assume
the calculation overflowed, and set the deadline to math.MaxInt64.

Fixes #14431

Change-Id: I54dbb4f02bc7ffb9cae8cf62e4e967e9c6541ec6
Reviewed-on: https://go-review.googlesource.com/19758
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Mikio Hara <mikioh.mikioh@gmail.com>

src/net/fd_poll_runtime.go

@@ -120,7 +120,13 @@ func (fd *netFD) setWriteDeadline(t time.Time) error {
 }
 
 func setDeadlineImpl(fd *netFD, t time.Time, mode int) error {
-	d := runtimeNano() + int64(t.Sub(time.Now()))
+	diff := int64(t.Sub(time.Now()))
+	d := runtimeNano() + diff
+	if d <= 0 && diff > 0 {
+		// If the user has a deadline in the future, but the delay calculation
+		// overflows, then set the deadline to the maximum possible value.
+		d = 1<<63 - 1
+	}
 	if t.IsZero() {
 		d = 0
 	}

src/net/timeout_test.go

@@ -26,6 +26,8 @@ var dialTimeoutTests = []struct {
 	{-5 * time.Second, 0, -5 * time.Second, 100 * time.Millisecond},
 	{0, -5 * time.Second, -5 * time.Second, 100 * time.Millisecond},
 	{-5 * time.Second, 5 * time.Second, -5 * time.Second, 100 * time.Millisecond}, // timeout over deadline
+	{-1 << 63, 0, time.Second, 100 * time.Millisecond},
+	{0, -1 << 63, time.Second, 100 * time.Millisecond},
 
 	{50 * time.Millisecond, 0, 100 * time.Millisecond, time.Second},
 	{0, 50 * time.Millisecond, 100 * time.Millisecond, time.Second},
@@ -99,6 +101,54 @@ func TestDialTimeout(t *testing.T) {
 	}
 }
 
+var dialTimeoutMaxDurationTests = []struct {
+	timeout time.Duration
+	delta   time.Duration // for deadline
+}{
+	// Large timeouts that will overflow an int64 unix nanos.
+	{1<<63 - 1, 0},
+	{0, 1<<63 - 1},
+}
+
+func TestDialTimeoutMaxDuration(t *testing.T) {
+	t.Parallel()
+
+	ln, err := newLocalListener("tcp")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer ln.Close()
+
+	for i, tt := range dialTimeoutMaxDurationTests {
+		ch := make(chan error)
+		max := time.NewTimer(100 * time.Millisecond)
+		defer max.Stop()
+		go func() {
+			d := Dialer{Timeout: tt.timeout}
+			if tt.delta != 0 {
+				d.Deadline = time.Now().Add(tt.delta)
+			}
+			c, err := d.Dial(ln.Addr().Network(), ln.Addr().String())
+			if err == nil {
+				c.Close()
+			}
+			ch <- err
+		}()
+
+		select {
+		case <-max.C:
+			t.Fatalf("#%d: Dial didn't return in an expected time", i)
+		case err := <-ch:
+			if perr := parseDialError(err); perr != nil {
+				t.Error(perr)
+			}
+			if err != nil {
+				t.Errorf("#%d: %v", i, err)
+			}
+		}
+	}
+}
+
 var acceptTimeoutTests = []struct {
 	timeout time.Duration
 	xerrs   [2]error // expected errors in transition