1. Apr 23, 2009
  2. Apr 22, 2009
  3. Apr 21, 2009
  4. Apr 20, 2009
    • Herbert Xu's avatar
      tun: Fix sk_sleep races when attaching/detaching · c40af84a
      Herbert Xu authored
      
      
      As the sk_sleep wait queue actually lives in tfile, which may be
      detached from the tun device, bad things will happen when we use
      sk_sleep after detaching.
      
      Since the tun device is the persistent data structure here (when
      requested by the user), it makes much more sense to have the wait
      queue live there.  There is no reason to have it in tfile at all
      since the only time we can wait is if we have a tun attached.
      In fact we already have a wait queue in tun_struct, so we might
      as well use it.
      
      Reported-by: default avatarEric W. Biederman <ebiederm@xmission.com>
      Tested-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
      Tested-by: default avatarPatrick McHardy <kaber@trash.net>
      Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      c40af84a
    • Herbert Xu's avatar
      tun: Only free a netdev when all tun descriptors are closed · 9c3fea6a
      Herbert Xu authored
      The commit c70f1829
      
       ("tun: Fix
      races between tun_net_close and free_netdev") fixed a race where
      an asynchronous deletion of a tun device can hose a poll(2) on
      a tun fd attached to that device.
      
      However, this came at the cost of moving the tun wait queue into
      the tun file data structure.  The problem with this is that it
      imposes restrictions on when and where the tun device can access
      the wait queue since the tun file may change at any time due to
      detaching and reattaching.
      
      In particular, now that we need to use the wait queue on the
      receive path it becomes difficult to properly synchronise this
      with the detachment of the tun device.
      
      This patch solves the original race in a different way.  Since
      the race is only because the underlying memory gets freed, we
      can prevent it simply by ensuring that we don't do that until
      all tun descriptors ever attached to the device (even if they
      have since be detached because they may still be sitting in poll)
      have been closed.
      
      This is done by using reference counting the attached tun file
      descriptors.  The refcount in tun->sk has been reappropriated
      for this purpose since it was already being used for that, albeit
      from the opposite angle.
      
      Note that we no longer zero tfile->tun since tun_get will return
      NULL anyway after the refcount on tfile hits zero.  Instead it
      represents whether this device has ever been attached to a device.
      
      Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      9c3fea6a