On Fri, Jan 24, 2020 at 03:08:18AM +0000, Sunil Muthuswamy wrote:
commit c742c59e1fbd ("hv_sock: Remove the accept port restriction")
Currently, hv_sock restricts the port the guest socket can accept connections on. hv_sock divides the socket port namespace into two parts for server side (listening socket), 0-0x7FFFFFFF & 0x80000000-0xFFFFFFFF (there are no restrictions on client port namespace). The first part (0-0x7FFFFFFF) is reserved for sockets where connections can be accepted. The second part (0x80000000-0xFFFFFFFF) is reserved for allocating ports for the peer (host) socket, once a connection is accepted. This reservation of the port namespace is specific to hv_sock and not known by the generic vsock library (ex: af_vsock). This is problematic because auto-binds/ephemeral ports are handled by the generic vsock library and it has no knowledge of this port reservation and could allocate a port that is not compatible with hv_sock (and legitimately so). The issue hasn't surfaced so far because the auto-bind code of vsock (__vsock_bind_stream) prior to the change 'VSOCK: bind to random port for VMADDR_PORT_ANY' would start walking up from LAST_RESERVED_PORT (1023) and start assigning ports. That will take a large number of iterations to hit 0x7FFFFFFF. But, after the above change to randomize port selection, the issue has started coming up more frequently. There has really been no good reason to have this port reservation logic in hv_sock from the get go. Reserving a local port for peer ports is not how things are handled generally. Peer ports should reflect the peer port. This fixes the issue by lifting the port reservation, and also returns the right peer port. Since the code converts the GUID to the peer port (by using the first 4 bytes), there is a possibility of conflicts, but that seems like a reasonable risk to take, given this is limited to vsock and that only applies to all local sockets.
Signed-off-by: Sunil Muthuswamy sunilmut@microsoft.com Signed-off-by: David S. Miller davem@davemloft.net
I'll queue it up when the current release is out in a day or so, thanks!