syscall: add bounds checking and error returns to ParseNetlinkMessage

Fixes #16681

Change-Id: I6ff7ec81fe48ab06be3aae5b7ff92e9dc70960c3
Reviewed-on: https://go-review.googlesource.com/26990
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Mikio Hara <mikioh.mikioh@gmail.com>

src/syscall/netlink_linux.go

@@ -129,10 +129,11 @@ func ParseNetlinkMessage(b []byte) ([]NetlinkMessage, error) {
 
 func netlinkMessageHeaderAndData(b []byte) (*NlMsghdr, []byte, int, error) {
 	h := (*NlMsghdr)(unsafe.Pointer(&b[0]))
-	if int(h.Len) < NLMSG_HDRLEN || int(h.Len) > len(b) {
+	l := nlmAlignOf(int(h.Len))
+	if int(h.Len) < NLMSG_HDRLEN || l > len(b) {
 		return nil, nil, 0, EINVAL
 	}
-	return h, b[NLMSG_HDRLEN:], nlmAlignOf(int(h.Len)), nil
+	return h, b[NLMSG_HDRLEN:], l, nil
 }
 
 // NetlinkRouteAttr represents a netlink route attribute.

src/syscall/syscall_linux_test.go

@@ -138,3 +138,31 @@ func deathSignalChild() {
 	fmt.Println("not ok")
 	os.Exit(1)
 }
+
+func TestParseNetlinkMessage(t *testing.T) {
+	for i, b := range [][]byte{
+		{103, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 2, 11, 0, 1, 0, 0, 0, 0, 5, 8, 0, 3,
+			0, 8, 0, 6, 0, 0, 0, 0, 1, 63, 0, 10, 0, 69, 16, 0, 59, 39, 82, 64, 0, 64, 6, 21, 89, 127, 0, 0,
+			1, 127, 0, 0, 1, 230, 228, 31, 144, 32, 186, 155, 211, 185, 151, 209, 179, 128, 24, 1, 86,
+			53, 119, 0, 0, 1, 1, 8, 10, 0, 17, 234, 12, 0, 17, 189, 126, 107, 106, 108, 107, 106, 13, 10,
+		},
+		{106, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 2, 11, 0, 1, 0, 0, 0, 0, 3, 8, 0, 3,
+			0, 8, 0, 6, 0, 0, 0, 0, 1, 66, 0, 10, 0, 69, 0, 0, 62, 230, 255, 64, 0, 64, 6, 85, 184, 127, 0, 0,
+			1, 127, 0, 0, 1, 237, 206, 31, 144, 73, 197, 128, 65, 250, 60, 192, 97, 128, 24, 1, 86, 253, 21, 0,
+			0, 1, 1, 8, 10, 0, 51, 106, 89, 0, 51, 102, 198, 108, 104, 106, 108, 107, 104, 108, 107, 104, 10,
+		},
+		{102, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 2, 11, 0, 1, 0, 0, 0, 0, 1, 8, 0, 3, 0,
+			8, 0, 6, 0, 0, 0, 0, 1, 62, 0, 10, 0, 69, 0, 0, 58, 231, 2, 64, 0, 64, 6, 85, 185, 127, 0, 0, 1, 127,
+			0, 0, 1, 237, 206, 31, 144, 73, 197, 128, 86, 250, 60, 192, 97, 128, 24, 1, 86, 104, 64, 0, 0, 1, 1, 8,
+			10, 0, 52, 198, 200, 0, 51, 135, 232, 101, 115, 97, 103, 103, 10,
+		},
+	} {
+		m, err := syscall.ParseNetlinkMessage(b)
+		if err != syscall.EINVAL {
+			t.Errorf("#%d: got %v; want EINVAL", i, err)
+		}
+		if m != nil {
+			t.Errorf("#%d: got %v; want nil", i, m)
+		}
+	}
+}