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/arm/include/asm/futex.h | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-) (limited to 'arch/arm/include') diff --git a/arch/arm/include/asm/futex.h b/arch/arm/include/asm/futex.h index 7133a862083..d20b78fce75 100644 --- a/arch/arm/include/asm/futex.h +++ b/arch/arm/include/asm/futex.h @@ -88,9 +88,10 @@ 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) { - int val; + int ret = 0, val; if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int))) return -EFAULT; @@ -99,24 +100,25 @@ futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval) * call sites. */ __asm__ __volatile__("@futex_atomic_cmpxchg_inatomic\n" - "1: " T(ldr) " %0, [%3]\n" - " teq %0, %1\n" + "1: " T(ldr) " %1, [%4]\n" + " teq %1, %2\n" " it eq @ explicit IT needed for the 2b label\n" - "2: " T(streq) " %2, [%3]\n" + "2: " T(streq) " %3, [%4]\n" "3:\n" " .pushsection __ex_table,\"a\"\n" " .align 3\n" " .long 1b, 4f, 2b, 4f\n" " .popsection\n" " .pushsection .fixup,\"ax\"\n" - "4: mov %0, %4\n" + "4: mov %0, %5\n" " b 3b\n" " .popsection" - : "=&r" (val) + : "+r" (ret), "=&r" (val) : "r" (oldval), "r" (newval), "r" (uaddr), "Ir" (-EFAULT) : "cc", "memory"); - return val; + *uval = val; + return ret; } #endif /* !SMP */ -- cgit v1.2.3-70-g09d2