Merge tag '9p-for-6.1-rc7' of

Pull 9p fixes from Dominique Martinet:

 - 9p now uses a variable size for its recv buffer, but every place
   hadn't been updated properly to use it and some buffer overflows have
   been found and needed fixing.

   There's still one place where msize is incorrectly used in a safety
   check (p9_check_errors), but all paths leading to it should already
   be avoiding overflows and that patch took a bit more time to get
   right for zero-copy requests so I'll send it for 6.2

 - yet another race condition in p9_conn_cancel introduced by a fix for
   a syzbot report in the same place. Maybe at some point we'll get it
   right without burning it all down...

* tag '9p-for-6.1-rc7' of
  9p/xen: check logical size for buffer size
  9p/fd: Use P9_HDRSZ for header size
  9p/fd: Fix write overflow in p9_read_work
  9p/fd: fix issue of list_del corruption in p9_fd_cancel()