1. 15 Feb, 2010 23 commits
  2. 12 Feb, 2010 5 commits
  3. 10 Feb, 2010 2 commits
  4. 07 Feb, 2010 1 commit
    • Linus Torvalds's avatar
      Fix race in tty_fasync() properly · 80e1e823
      Linus Torvalds authored
      This reverts commit 70362511 ("tty: fix race in tty_fasync") and
      commit b04da8bf ("fnctl: f_modown should call write_lock_irqsave/
      restore") that tried to fix up some of the fallout but was incomplete.
      
      It turns out that we really cannot hold 'tty->ctrl_lock' over calling
      __f_setown, because not only did that cause problems with interrupt
      disables (which the second commit fixed), it also causes a potential
      ABBA deadlock due to lock ordering.
      
      Thanks to Tetsuo Handa for following up on the issue, and running
      lockdep to show the problem.  It goes roughly like this:
      
       - f_getown gets filp->f_owner.lock for reading without interrupts
         disabled, so an interrupt that happens while that lock is held can
         cause a lockdep chain from f_owner.lock -> sighand->siglock.
      
       - at the same time, the tty->ctrl_lock -> f_owner.lock chain that
         commit 70362511
      
       introduced, together with the pre-existing
         sighand->siglock -> tty->ctrl_lock chain means that we have a lock
         dependency the other way too.
      
      So instead of extending tty->ctrl_lock over the whole __f_setown() call,
      we now just take a reference to the 'pid' structure while holding the
      lock, and then release it after having done the __f_setown.  That still
      guarantees that 'struct pid' won't go away from under us, which is all
      we really ever needed.
      Reported-and-tested-by: default avatarTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
      Acked-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
      Acked-by: default avatarAmérico Wang <xiyou.wangcong@gmail.com>
      Cc: stable@kernel.org
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      80e1e823
  5. 06 Feb, 2010 4 commits
  6. 05 Feb, 2010 5 commits