bpf: Fix verifier assumptions about socket->sk

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix verifier assumptions about socket->sk The verifier assumes that 'sk' field in 'struct socket' is valid and non-NULL when 'socket' pointer itself is trusted and non-NULL. That may not be the case when socket was just created and passed to LSM socket_accept hook. Fix this verifier assumption and adjust tests.

References

• https://git.kernel.org/stable/c/39f8a29330f433000e716eefc4b9abda05b71a82
• https://git.kernel.org/stable/c/6f5ae91172a93abac9720ba94edf3ec8f4d7f24f
• https://git.kernel.org/stable/c/c58ccdd2483a1d990748cdaf94206b5d5986a001
• https://git.kernel.org/stable/c/0db63c0b86e981a1e97d2596d64ceceba1a5470e