From 37a9d912b24f96a0591773e6e6c3642991ae5a70 Mon Sep 17 00:00:00 2001 From: Michel Lespinasse Date: Thu, 10 Mar 2011 18:48:51 -0800 Subject: futex: Sanitize cmpxchg_futex_value_locked API The cmpxchg_futex_value_locked API was funny in that it returned either the original, user-exposed futex value OR an error code such as -EFAULT. This was confusing at best, and could be a source of livelocks in places that retry the cmpxchg_futex_value_locked after trying to fix the issue by running fault_in_user_writeable(). This change makes the cmpxchg_futex_value_locked API more similar to the get_futex_value_locked one, returning an error code and updating the original value through a reference argument. Signed-off-by: Michel Lespinasse Acked-by: Chris Metcalf [tile] Acked-by: Tony Luck [ia64] Acked-by: Thomas Gleixner Tested-by: Michal Simek [microblaze] Acked-by: David Howells [frv] Cc: Darren Hart Cc: Peter Zijlstra Cc: Matt Turner Cc: Russell King Cc: Ralf Baechle Cc: "James E.J. Bottomley" Cc: Benjamin Herrenschmidt Cc: Martin Schwidefsky Cc: Paul Mundt Cc: "David S. Miller" Cc: Linus Torvalds LKML-Reference: <20110311024851.GC26122@google.com> Signed-off-by: Thomas Gleixner --- arch/ia64/include/asm/futex.h | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) (limited to 'arch/ia64') diff --git a/arch/ia64/include/asm/futex.h b/arch/ia64/include/asm/futex.h index c7f0f06..b072840 100644 --- a/arch/ia64/include/asm/futex.h +++ b/arch/ia64/include/asm/futex.h @@ -100,23 +100,26 @@ futex_atomic_op_inuser (int encoded_op, int __user *uaddr) } static inline int -futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval) +futex_atomic_cmpxchg_inatomic(int *uval, int __user *uaddr, + int oldval, int newval) { if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int))) return -EFAULT; { - register unsigned long r8 __asm ("r8"); + register unsigned long r8 __asm ("r8") = 0; + unsigned long prev; __asm__ __volatile__( " mf;; \n" " mov ar.ccv=%3;; \n" "[1:] cmpxchg4.acq %0=[%1],%2,ar.ccv \n" " .xdata4 \"__ex_table\", 1b-., 2f-. \n" "[2:]" - : "=r" (r8) + : "=r" (prev) : "r" (uaddr), "r" (newval), "rO" ((long) (unsigned) oldval) : "memory"); + *uval = prev; return r8; } } -- cgit v1.1