Re: [PATCH v5 0/6] rfcomm: Implement rfcomm as a proper tty_port

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On 07/29/2013 11:08 AM, Gianluca Anzolin wrote:
This patchset addresses an issue with the rfcomm tty driver in the
current stable kernels that manifests itself as a sudden lockup of the
whole machine or as a OOPS if we are lucky enough (I wasn't).

Triggering the problem is very easy:

1) establish a bluetooth connection with a bluetooth host
2) open the tty it provides with some program
3) turn off the bluetooth host or take it out of range

After a timeout the machine freezes.

Another way to trigger these lockups is to simply release the rfcomm
tty.

This happens beacuse the underlying tty_struct objects and tty_port
objects are freed while being used: the code doesn't take proper
references to them.

The following patches address the problem by implementing a proper
tty_port driver for rfcomm.

There are still some issues left: one relevant to flow control (which is
also missing in the current code) and another relevant to a corner case
in rfcomm_dev_state_change() that I intend to fix with a future patch.
They are commented with a FIXME.

Changes from v4:
   [PATCH 3/6]: left the debug message in rfcomm_tty_open()
   [PATCH 5/6]: always use !test_and_set_bit() to release the tty_port

I reviewed these changes and retested. All ok.

Regards,
Peter Hurley


Thank you,
Gianluca

Gianluca Anzolin (6):
   rfcomm: Take proper tty_struct references
   rfcomm: Remove the device from the list in the destructor
   rfcomm: Move the tty initialization and cleanup out of open/close
   rfcomm: Implement .activate, .shutdown and .carrier_raised methods
   rfcomm: Fix the reference counting of tty_port
   rfcomm: Purge the dlc->tx_queue to avoid circular dependency

  net/bluetooth/rfcomm/tty.c | 271 +++++++++++++++++++++------------------------
  1 file changed, 126 insertions(+), 145 deletions(-)


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