tree 66b92176051147b87031cc2755639c39f8a900f8
parent 995612178c88407d8330f580ba6572cb8b284dd8
author Thomas Gleixner <tglx@linutronix.de> 1300095275 +0100
committer Thomas Gleixner <tglx@linutronix.de> 1300133327 +0100

futex: Deobfuscate handle_futex_death()

handle_futex_death() uses futex_atomic_cmpxchg_inatomic() without
disabling page faults. That's ok, but totally non obvious.

We don't hold locks so we actually can and want to fault here, because
the get_user() before futex_atomic_cmpxchg_inatomic() does not
guarantee a R/W mapping.

We could just add a big fat comment to explain this, but actually
changing the code so that the functionality is entirely clear is
better.

Use the helper function which disables page faults around the
futex_atomic_cmpxchg_inatomic() and handle a fault with a call to
fault_in_user_writeable() as all other places in the futex code do as
well.

Pointed-out-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Darren Hart <darren@dvhart.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: David Howells <dhowells@redhat.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Chris Metcalf <cmetcalf@tilera.com>
LKML-Reference: <alpine.LFD.2.00.1103141126590.2787@localhost6.localdomain6>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>