In the Linux kernel, the following vulnerability has been resolved:

af_unix: Return immediately when manage_oob() returns NULL for 0-length buffer.

Fahad Alharbi reported that recv(0, MSG_PEEK) triggers busy-wait
in unix_stream_read_generic() if recv() is blocking and the last
skb in the queue is MSG_OOB skb.

In such a situation, TCP returns 0 immediately regardless of
blocking or non-blocking.

Let's follow the behaviour.