rxrpc: Fix a race between socket set up and I/O thread creation

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: rxrpc: Fix a race between socket set up and I/O thread creation In rxrpc_open_socket(), it sets up the socket and then sets up the I/O thread that will handle it. This is a problem, however, as there's a gap between the two phases in which a packet may come into rxrpc_encap_rcv() from the UDP packet but we oops when trying to wake the not-yet created I/O thread. As a quick fix, just make rxrpc_encap_rcv() discard the packet if there's no I/O thread yet. A better, but more intrusive fix would perhaps be to rearrange things such that the socket creation is done by the I/O thread.

References

• https://git.kernel.org/stable/c/cdf4bbbdb956d7426f687f38757ebca2a2759a0f
• https://git.kernel.org/stable/c/56e415202b8a17de6496f4023e545fcb66f118ec
• https://git.kernel.org/stable/c/c64f5fc95e9612fdf75587c8e21e494e614c18e2
• https://git.kernel.org/stable/c/bc212465326e8587325f520a052346f0b57360e6