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.
https://git.kernel.org/stable/c/d5dd55b316ca229a4cbf11729483ba5bb57233e7
https://git.kernel.org/stable/c/c81c5be3826c8467945b964d0cf7f7b3d65461db
https://git.kernel.org/stable/c/6e5ee08eb5858d175da6768d75d163817b6a9d4a
https://git.kernel.org/stable/c/3d3c7a3df66b2ca3d2cd1a2a0c37eb701feba713