[op] Make PacketBuffer Clone() do a deeper copy.

Earlier PacketBuffer.Clone() would do a shallow top level copy of the packet
buffer - which involved sharing the *buffer.Buffer between packets. Reading
or writing to the buffer in one packet would impact the other.

This caused modifications in one packet to affect the other's pkt.Views() which
is not desired. Change the clone to do a deeper copy of the underlying buffer
list and buffer pointers. The payload buffers (which are immutable) are still
shared. This change makes the Clone() operation more expensive as we now need to
allocate the entire buffer list.

Added unit test to test integrity of packet data after cloning.

Reported-by: syzbot+7ffff9a82a227b8f2e31@syzkaller.appspotmail.com
Reported-by: syzbot+7d241de0d9072b2b6075@syzkaller.appspotmail.com
Reported-by: syzbot+212bc4d75802fa461521@syzkaller.appspotmail.com
PiperOrigin-RevId: 390277713

1 files changed, 26 insertions, 0 deletions

diff --git a/pkg/tcpip/stack/packet_buffer_test.go b/pkg/tcpip/stack/packet_buffer_test.go
index a8da34992..87b023445 100644
--- a/pkg/tcpip/stack/packet_buffer_test.go
+++ b/pkg/tcpip/stack/packet_buffer_test.go
@@ -123,6 +123,32 @@ func TestPacketHeaderPush(t *testing.T) {
 	}
 }
 
+func TestPacketBufferClone(t *testing.T) {
+	data := concatViews(makeView(20), makeView(30), makeView(40))
+	pk := NewPacketBuffer(PacketBufferOptions{
+		// Make a copy of data to make sure our truth data won't be taint by
+		// PacketBuffer.
+		Data: buffer.NewViewFromBytes(data).ToVectorisedView(),
+	})
+
+	bytesToDelete := 30
+	originalSize := data.Size()
+
+	clonedPks := []*PacketBuffer{
+		pk.Clone(),
+		pk.CloneToInbound(),
+	}
+	pk.Data().DeleteFront(bytesToDelete)
+	if got, want := pk.Data().Size(), originalSize-bytesToDelete; got != want {
+		t.Errorf("original packet was not changed: size expected = %d, got = %d", want, got)
+	}
+	for _, clonedPk := range clonedPks {
+		if got := clonedPk.Data().Size(); got != originalSize {
+			t.Errorf("cloned packet should not be modified: expected size = %d, got = %d", originalSize, got)
+		}
+	}
+}
+
 func TestPacketHeaderConsume(t *testing.T) {
 	for _, test := range []struct {
 		name      string