1. 16 Mar, 2017 1 commit
  2. 31 Aug, 2016 1 commit
    • Vitaly Kuznetsov's avatar
      Drivers: hv: utils: fix a race on userspace daemons registration · e0fa3e5e
      Vitaly Kuznetsov authored
      
      
      Background: userspace daemons registration protocol for Hyper-V utilities
      drivers has two steps:
      1) daemon writes its own version to kernel
      2) kernel reads it and replies with module version
      at this point we consider the handshake procedure being completed and we
      do hv_poll_channel() transitioning the utility device to HVUTIL_READY
      state. At this point we're ready to handle messages from kernel.
      
      When hvutil_transport is in HVUTIL_TRANSPORT_CHARDEV mode we have a
      single buffer for outgoing message. hvutil_transport_send() puts to this
      buffer and till the buffer is cleared with hvt_op_read() returns -EFAULT
      to all consequent calls. Host<->guest protocol guarantees there is no more
      than one request at a time and we will not get new requests till we reply
      to the previous one so this single message buffer is enough.
      
      Now to the race. When we finish negotiation procedure and send kernel
      module version to userspace with hvutil_transport_send() it goes into the
      above mentioned buffer and if the daemon is slow enough to read it from
      there we can get a collision when a request from the host comes, we won't
      be able to put anything to the buffer so the request will be lost. To
      solve the issue we need to know when the negotiation is really done (when
      the version message is read by the daemon) and transition to HVUTIL_READY
      state after this happens. Implement a callback on read to support this.
      Old style netlink communication is not affected by the change, we don't
      really know when these messages are delivered but we don't have a single
      message buffer there.
      
      Reported-by: default avatarBarry Davis <barry_davis@stormagic.com>
      Signed-off-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
      Signed-off-by: default avatarK. Y. Srinivasan <kys@microsoft.com>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      e0fa3e5e
  3. 02 Mar, 2016 1 commit
  4. 21 Dec, 2015 1 commit
  5. 15 Dec, 2015 6 commits
  6. 05 Aug, 2015 1 commit
  7. 24 May, 2015 1 commit