1. 30 Jun, 2010 1 commit
    • Michal Hocko's avatar
      futex: futex_find_get_task remove credentails check · 7a0ea09a
      Michal Hocko authored
      
      
      futex_find_get_task is currently used (through lookup_pi_state) from two
      contexts, futex_requeue and futex_lock_pi_atomic.  None of the paths
      looks it needs the credentials check, though.  Different (e)uids
      shouldn't matter at all because the only thing that is important for
      shared futex is the accessibility of the shared memory.
      
      The credentail check results in glibc assert failure or process hang (if
      glibc is compiled without assert support) for shared robust pthread
      mutex with priority inheritance if a process tries to lock already held
      lock owned by a process with a different euid:
      
      pthread_mutex_lock.c:312: __pthread_mutex_lock_full: Assertion `(-(e)) != 3 || !robust' failed.
      
      The problem is that futex_lock_pi_atomic which is called when we try to
      lock already held lock checks the current holder (tid is stored in the
      futex value) to get the PI state.  It uses lookup_pi_state which in turn
      gets task struct from futex_find_get_task.  ESRCH is returned either
      when the task is not found or if credentials check fails.
      
      futex_lock_pi_atomic simply returns if it gets ESRCH.  glibc code,
      however, doesn't expect that robust lock returns with ESRCH because it
      should get either success or owner died.
      Signed-off-by: default avatarMichal Hocko <mhocko@suse.cz>
      Acked-by: default avatarDarren Hart <dvhltc@us.ibm.com>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Nick Piggin <npiggin@suse.de>
      Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      7a0ea09a
  2. 29 Jun, 2010 22 commits
  3. 28 Jun, 2010 7 commits
  4. 27 Jun, 2010 10 commits