Correctly return EMSGSIZE when packet is too big in raw socket.

IPv4 previously accepts the packet, while IPv6 panics. Neither is the behavior
in Linux.

splice() in Linux has different behavior than in gVisor. This change documents
it in the SpliceTooLong test.

Reported-by: syzbot+b550e78e5c24d1d521f2@syzkaller.appspotmail.com
PiperOrigin-RevId: 352091286

pkg/tcpip/network/ipv4/igmp.go

@@ -262,13 +262,15 @@ func (igmp *igmpState) writePacket(destAddress tcpip.Address, groupAddress tcpip
 	localAddr := addressEndpoint.AddressWithPrefix().Address
 	addressEndpoint.DecRef()
 	addressEndpoint = nil
-	igmp.ep.addIPHeader(localAddr, destAddress, pkt, stack.NetworkHeaderParams{
+	if err := igmp.ep.addIPHeader(localAddr, destAddress, pkt, stack.NetworkHeaderParams{
 		Protocol: header.IGMPProtocolNumber,
 		TTL:      header.IGMPTTL,
 		TOS:      stack.DefaultTOS,
 	}, header.IPv4OptionsSerializer{
 		&header.IPv4SerializableRouterAlertOption{},
-	})
+	}); err != nil {
+		panic(fmt.Sprintf("failed to add IP header: %s", err))
+	}
 
 	sentStats := igmp.ep.protocol.stack.Stats().IGMP.PacketsSent
 	if err := igmp.ep.nic.WritePacketToRemote(header.EthernetAddressFromMulticastIPv4Address(destAddress), nil /* gso */, ProtocolNumber, pkt); err != nil {

pkg/tcpip/network/ipv4/ipv4.go

@@ -237,7 +237,7 @@ func (e *endpoint) NetworkProtocolNumber() tcpip.NetworkProtocolNumber {
 	return e.protocol.Number()
 }
 
-func (e *endpoint) addIPHeader(srcAddr, dstAddr tcpip.Address, pkt *stack.PacketBuffer, params stack.NetworkHeaderParams, options header.IPv4OptionsSerializer) {
+func (e *endpoint) addIPHeader(srcAddr, dstAddr tcpip.Address, pkt *stack.PacketBuffer, params stack.NetworkHeaderParams, options header.IPv4OptionsSerializer) *tcpip.Error {
 	hdrLen := header.IPv4MinimumSize
 	var optLen int
 	if options != nil {
@@ -245,19 +245,19 @@ func (e *endpoint) addIPHeader(srcAddr, dstAddr tcpip.Address, pkt *stack.Packet
 	}
 	hdrLen += optLen
 	if hdrLen > header.IPv4MaximumHeaderSize {
-		// Since we have no way to report an error we must either panic or create
-		// a packet which is different to what was requested. Choose panic as this
-		// would be a programming error that should be caught in testing.
-		panic(fmt.Sprintf("IPv4 Options %d bytes, Max %d", optLen, header.IPv4MaximumOptionsSize))
+		return tcpip.ErrMessageTooLong
 	}
 	ip := header.IPv4(pkt.NetworkHeader().Push(hdrLen))
-	length := uint16(pkt.Size())
+	length := pkt.Size()
+	if length > math.MaxUint16 {
+		return tcpip.ErrMessageTooLong
+	}
 	// RFC 6864 section 4.3 mandates uniqueness of ID values for non-atomic
 	// datagrams. Since the DF bit is never being set here, all datagrams
 	// are non-atomic and need an ID.
 	id := atomic.AddUint32(&e.protocol.ids[hashRoute(srcAddr, dstAddr, params.Protocol, e.protocol.hashIV)%buckets], 1)
 	ip.Encode(&header.IPv4Fields{
-		TotalLength: length,
+		TotalLength: uint16(length),
 		ID:          uint16(id),
 		TTL:         params.TTL,
 		TOS:         params.TOS,
@@ -268,6 +268,7 @@ func (e *endpoint) addIPHeader(srcAddr, dstAddr tcpip.Address, pkt *stack.Packet
 	})
 	ip.SetChecksum(^ip.CalculateChecksum())
 	pkt.NetworkProtocolNumber = ProtocolNumber
+	return nil
 }
 
 // handleFragments fragments pkt and calls the handler function on each
@@ -295,7 +296,9 @@ func (e *endpoint) handleFragments(r *stack.Route, gso *stack.GSO, networkMTU ui
 
 // WritePacket writes a packet to the given destination address and protocol.
 func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, params stack.NetworkHeaderParams, pkt *stack.PacketBuffer) *tcpip.Error {
-	e.addIPHeader(r.LocalAddress, r.RemoteAddress, pkt, params, nil /* options */)
+	if err := e.addIPHeader(r.LocalAddress, r.RemoteAddress, pkt, params, nil /* options */); err != nil {
+		return err
+	}
 
 	// iptables filtering. All packets that reach here are locally
 	// generated.
@@ -383,7 +386,10 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
 	}
 
 	for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
-		e.addIPHeader(r.LocalAddress, r.RemoteAddress, pkt, params, nil /* options */)
+		if err := e.addIPHeader(r.LocalAddress, r.RemoteAddress, pkt, params, nil /* options */); err != nil {
+			return 0, err
+		}
+
 		networkMTU, err := calculateNetworkMTU(e.nic.MTU(), uint32(pkt.NetworkHeader().View().Size()))
 		if err != nil {
 			r.Stats().IP.OutgoingPacketErrors.IncrementBy(uint64(pkts.Len()))

pkg/tcpip/network/ipv6/ipv6.go

@@ -553,11 +553,11 @@ func (e *endpoint) MaxHeaderLength() uint16 {
 	return e.nic.MaxHeaderLength() + header.IPv6MinimumSize
 }
 
-func (e *endpoint) addIPHeader(srcAddr, dstAddr tcpip.Address, pkt *stack.PacketBuffer, params stack.NetworkHeaderParams, extensionHeaders header.IPv6ExtHdrSerializer) {
+func (e *endpoint) addIPHeader(srcAddr, dstAddr tcpip.Address, pkt *stack.PacketBuffer, params stack.NetworkHeaderParams, extensionHeaders header.IPv6ExtHdrSerializer) *tcpip.Error {
 	extHdrsLen := extensionHeaders.Length()
 	length := pkt.Size() + extensionHeaders.Length()
 	if length > math.MaxUint16 {
-		panic(fmt.Sprintf("IPv6 payload too large: %d, must be <= %d", length, math.MaxUint16))
+		return tcpip.ErrMessageTooLong
 	}
 	ip := header.IPv6(pkt.NetworkHeader().Push(header.IPv6MinimumSize + extHdrsLen))
 	ip.Encode(&header.IPv6Fields{
@@ -570,6 +570,7 @@ func (e *endpoint) addIPHeader(srcAddr, dstAddr tcpip.Address, pkt *stack.Packet
 		ExtensionHeaders:  extensionHeaders,
 	})
 	pkt.NetworkProtocolNumber = ProtocolNumber
+	return nil
 }
 
 func packetMustBeFragmented(pkt *stack.PacketBuffer, networkMTU uint32, gso *stack.GSO) bool {
@@ -622,7 +623,9 @@ func (e *endpoint) handleFragments(r *stack.Route, gso *stack.GSO, networkMTU ui
 
 // WritePacket writes a packet to the given destination address and protocol.
 func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, params stack.NetworkHeaderParams, pkt *stack.PacketBuffer) *tcpip.Error {
-	e.addIPHeader(r.LocalAddress, r.RemoteAddress, pkt, params, nil /* extensionHeaders */)
+	if err := e.addIPHeader(r.LocalAddress, r.RemoteAddress, pkt, params, nil /* extensionHeaders */); err != nil {
+		return err
+	}
 
 	// iptables filtering. All packets that reach here are locally
 	// generated.
@@ -711,7 +714,9 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
 
 	linkMTU := e.nic.MTU()
 	for pb := pkts.Front(); pb != nil; pb = pb.Next() {
-		e.addIPHeader(r.LocalAddress, r.RemoteAddress, pb, params, nil /* extensionHeaders */)
+		if err := e.addIPHeader(r.LocalAddress, r.RemoteAddress, pb, params, nil /* extensionHeaders */); err != nil {
+			return 0, err
+		}
 
 		networkMTU, err := calculateNetworkMTU(linkMTU, uint32(pb.NetworkHeader().View().Size()))
 		if err != nil {

pkg/tcpip/network/ipv6/mld.go

@@ -249,10 +249,12 @@ func (mld *mldState) writePacket(destAddress, groupAddress tcpip.Address, mldTyp
 		Data:               buffer.View(icmp).ToVectorisedView(),
 	})
 
-	mld.ep.addIPHeader(localAddress, destAddress, pkt, stack.NetworkHeaderParams{
+	if err := mld.ep.addIPHeader(localAddress, destAddress, pkt, stack.NetworkHeaderParams{
 		Protocol: header.ICMPv6ProtocolNumber,
 		TTL:      header.MLDHopLimit,
-	}, extensionHeaders)
+	}, extensionHeaders); err != nil {
+		panic(fmt.Sprintf("failed to add IP header: %s", err))
+	}
 	if err := mld.ep.nic.WritePacketToRemote(header.EthernetAddressFromMulticastIPv6Address(destAddress), nil /* gso */, ProtocolNumber, pkt); err != nil {
 		sentStats.Dropped.Increment()
 		return false, err

pkg/tcpip/network/ipv6/ndp.go

@@ -732,10 +732,12 @@ func (ndp *ndpState) sendDADPacket(addr tcpip.Address, addressEndpoint stack.Add
 	})
 
 	sent := ndp.ep.protocol.stack.Stats().ICMP.V6.PacketsSent
-	ndp.ep.addIPHeader(header.IPv6Any, snmc, pkt, stack.NetworkHeaderParams{
+	if err := ndp.ep.addIPHeader(header.IPv6Any, snmc, pkt, stack.NetworkHeaderParams{
 		Protocol: header.ICMPv6ProtocolNumber,
 		TTL:      header.NDPHopLimit,
-	}, nil /* extensionHeaders */)
+	}, nil /* extensionHeaders */); err != nil {
+		panic(fmt.Sprintf("failed to add IP header: %s", err))
+	}
 
 	if err := ndp.ep.nic.WritePacketToRemote(header.EthernetAddressFromMulticastIPv6Address(snmc), nil /* gso */, ProtocolNumber, pkt); err != nil {
 		sent.Dropped.Increment()
@@ -1854,11 +1856,12 @@ func (ndp *ndpState) startSolicitingRouters() {
 		})
 
 		sent := ndp.ep.protocol.stack.Stats().ICMP.V6.PacketsSent
-		ndp.ep.addIPHeader(localAddr, header.IPv6AllRoutersMulticastAddress, pkt, stack.NetworkHeaderParams{
+		if err := ndp.ep.addIPHeader(localAddr, header.IPv6AllRoutersMulticastAddress, pkt, stack.NetworkHeaderParams{
 			Protocol: header.ICMPv6ProtocolNumber,
 			TTL:      header.NDPHopLimit,
-		}, nil /* extensionHeaders */)
-
+		}, nil /* extensionHeaders */); err != nil {
+			panic(fmt.Sprintf("failed to add IP header: %s", err))
+		}
 		if err := ndp.ep.nic.WritePacketToRemote(header.EthernetAddressFromMulticastIPv6Address(header.IPv6AllRoutersMulticastAddress), nil /* gso */, ProtocolNumber, pkt); err != nil {
 			sent.Dropped.Increment()
 			log.Printf("startSolicitingRouters: error writing NDP router solicit message on NIC(%d); err = %s", ndp.ep.nic.ID(), err)

test/syscalls/linux/packet_socket_raw.cc

@@ -678,6 +678,58 @@ TEST_P(RawPacketTest, GetSocketAcceptConn) {
 INSTANTIATE_TEST_SUITE_P(AllInetTests, RawPacketTest,
                          ::testing::Values(ETH_P_IP, ETH_P_ALL));
 
+class RawPacketMsgSizeTest : public ::testing::TestWithParam<TestAddress> {};
+
+TEST_P(RawPacketMsgSizeTest, SendTooLong) {
+  SKIP_IF(!ASSERT_NO_ERRNO_AND_VALUE(HaveCapability(CAP_NET_RAW)));
+
+  TestAddress addr = GetParam().WithPort(kPort);
+
+  FileDescriptor udp_sock =
+      ASSERT_NO_ERRNO_AND_VALUE(Socket(addr.family(), SOCK_RAW, IPPROTO_UDP));
+
+  ASSERT_THAT(
+      connect(udp_sock.get(), reinterpret_cast<struct sockaddr*>(&addr.addr),
+              addr.addr_len),
+      SyscallSucceeds());
+
+  const char buf[65536] = {};
+  ASSERT_THAT(send(udp_sock.get(), buf, sizeof(buf), 0),
+              SyscallFailsWithErrno(EMSGSIZE));
+}
+
+TEST_P(RawPacketMsgSizeTest, SpliceTooLong) {
+  SKIP_IF(!ASSERT_NO_ERRNO_AND_VALUE(HaveCapability(CAP_NET_RAW)));
+
+  const char buf[65536] = {};
+  int fds[2];
+  ASSERT_THAT(pipe(fds), SyscallSucceeds());
+  ASSERT_THAT(write(fds[1], buf, sizeof(buf)),
+              SyscallSucceedsWithValue(sizeof(buf)));
+
+  TestAddress addr = GetParam().WithPort(kPort);
+
+  FileDescriptor udp_sock =
+      ASSERT_NO_ERRNO_AND_VALUE(Socket(addr.family(), SOCK_RAW, IPPROTO_UDP));
+
+  ASSERT_THAT(
+      connect(udp_sock.get(), reinterpret_cast<struct sockaddr*>(&addr.addr),
+              addr.addr_len),
+      SyscallSucceeds());
+
+  ssize_t n = splice(fds[0], nullptr, udp_sock.get(), nullptr, sizeof(buf), 0);
+  if (IsRunningOnGvisor()) {
+    EXPECT_THAT(n, SyscallFailsWithErrno(EMSGSIZE));
+  } else {
+    // TODO(gvisor.dev/issue/138): Linux sends out multiple UDP datagrams, each
+    // of the size of a page.
+    EXPECT_THAT(n, SyscallSucceedsWithValue(sizeof(buf)));
+  }
+}
+
+INSTANTIATE_TEST_SUITE_P(AllRawPacketMsgSizeTest, RawPacketMsgSizeTest,
+                         ::testing::Values(V4Loopback(), V6Loopback()));
+
 }  // namespace
 
 }  // namespace testing

test/syscalls/linux/socket_test_util.cc

@@ -791,6 +791,19 @@ void RecvNoData(int sock) {
               SyscallFailsWithErrno(EAGAIN));
 }
 
+TestAddress TestAddress::WithPort(uint16_t port) const {
+  TestAddress addr = *this;
+  switch (addr.family()) {
+    case AF_INET:
+      reinterpret_cast<sockaddr_in*>(&addr.addr)->sin_port = htons(port);
+      break;
+    case AF_INET6:
+      reinterpret_cast<sockaddr_in6*>(&addr.addr)->sin6_port = htons(port);
+      break;
+  }
+  return addr;
+}
+
 TestAddress V4Any() {
   TestAddress t("V4Any");
   t.addr.ss_family = AF_INET;

test/syscalls/linux/socket_test_util.h

@@ -486,9 +486,14 @@ struct TestAddress {
   sockaddr_storage addr;
   socklen_t addr_len;
 
-  int family() const { return addr.ss_family; }
   explicit TestAddress(std::string description = "")
       : description(std::move(description)), addr(), addr_len() {}
+
+  int family() const { return addr.ss_family; }
+
+  // Returns a new TestAddress with specified port. If port is not supported,
+  // the same TestAddress is returned.
+  TestAddress WithPort(uint16_t port) const;
 };
 
 constexpr char kMulticastAddress[] = "224.0.2.1";