ia64: fix futex_atomic_cmpxchg_inatomic()
authorLuck, Tony <tony.luck@intel.com>
Mon, 16 Apr 2012 23:28:01 +0000 (16:28 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Tue, 17 Apr 2012 01:30:01 +0000 (18:30 -0700)
commitc76f39bddb84f93f70a5520d9253ec0317bec216
treea131e6a03bc6eba668966e0795c44ce8fc8c26ca
parentc06a9ebdb7a4f4823d4225fe789d8c20a1d534eb
ia64: fix futex_atomic_cmpxchg_inatomic()

Michel Lespinasse cleaned up the futex calling conventions in commit
37a9d912b24f ("futex: Sanitize cmpxchg_futex_value_locked API").

But the ia64 implementation was subtly broken.  Gcc does not know that
register "r8" will be updated by the fault handler if the cmpxchg
instruction takes an exception.  So it feels safe in letting the
initialization of r8 slide to after the cmpxchg.  Result: we always
return 0 whether the user address faulted or not.

Fix by moving the initialization of r8 into the __asm__ code so gcc
won't move it.

Reported-by: <emeric.maschino@gmail.com>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=42757
Tested-by: <emeric.maschino@gmail.com>
Acked-by: Michel Lespinasse <walken@google.com>
Cc: stable@vger.kernel.org # v2.6.39+
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
arch/ia64/include/asm/futex.h