ksmbd: validate session id and tree id in compound request

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: validate session id and tree id in compound request `smb2_get_msg()` in smb2_get_ksmbd_tcon() and smb2_check_user_session() will always return the first request smb2 header in a compound request. if `SMB2_TREE_CONNECT_HE` is the first command in compound request, will return 0, i.e. The tree id check is skipped. This patch use ksmbd_req_buf_next() to get current command in compound.

References

• https://git.kernel.org/stable/c/017d85c94f02090a87f4a473dbe0d6ee0da72693
• https://git.kernel.org/stable/c/becb5191d1d5fdfca0198a2e37457bbbf4fe266f
• https://git.kernel.org/stable/c/4c2b350b2e269e3fd17bbfa42de1b42775b777ac
• https://git.kernel.org/stable/c/3df0411e132ee74a87aa13142dfd2b190275332e