From 306a82881b14d950d59e0b59a55093a07d82aa9a Mon Sep 17 00:00:00 2001
From: Paul Mackerras <paulus@samba.org>
Date: Mon, 13 Apr 2009 14:09:09 +0000
Subject: [PATCH] powerpc: Fix data-corrupting bug in __futex_atomic_op
Richard Henderson pointed out that the powerpc __futex_atomic_op has a
bug: it will write the wrong value if the stwcx. fails and it has to
retry the lwarx/stwcx. loop, since 'oparg' will have been overwritten
by the result from the first time around the loop. This happens
because it uses the same register for 'oparg' (an input) as it uses
for the result.
This fixes it by using separate registers for 'oparg' and 'ret'.
Cc: stable@kernel.org
Signed-off-by: Paul Mackerras <paulus@samba.org>
---
arch/powerpc/include/asm/futex.h | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/arch/powerpc/include/asm/futex.h b/arch/powerpc/include/asm/futex.h
index 6d406c5c5de403..9696cc36d2dcf5 100644
--- a/arch/powerpc/include/asm/futex.h
+++ b/arch/powerpc/include/asm/futex.h
@@ -27,7 +27,7 @@
PPC_LONG "1b,4b,2b,4b\n" \
".previous" \
: "=&r" (oldval), "=&r" (ret) \
- : "b" (uaddr), "i" (-EFAULT), "1" (oparg) \
+ : "b" (uaddr), "i" (-EFAULT), "r" (oparg) \
: "cr0", "memory")
static inline int futex_atomic_op_inuser (int encoded_op, int __user *uaddr)
@@ -47,19 +47,19 @@ static inline int futex_atomic_op_inuser (int encoded_op, int __user *uaddr)
switch (op) {
case FUTEX_OP_SET:
- __futex_atomic_op("", ret, oldval, uaddr, oparg);
+ __futex_atomic_op("mr %1,%4\n", ret, oldval, uaddr, oparg);
break;
case FUTEX_OP_ADD:
- __futex_atomic_op("add %1,%0,%1\n", ret, oldval, uaddr, oparg);
+ __futex_atomic_op("add %1,%0,%4\n", ret, oldval, uaddr, oparg);
break;
case FUTEX_OP_OR:
- __futex_atomic_op("or %1,%0,%1\n", ret, oldval, uaddr, oparg);
+ __futex_atomic_op("or %1,%0,%4\n", ret, oldval, uaddr, oparg);
break;
case FUTEX_OP_ANDN:
- __futex_atomic_op("andc %1,%0,%1\n", ret, oldval, uaddr, oparg);
+ __futex_atomic_op("andc %1,%0,%4\n", ret, oldval, uaddr, oparg);
break;
case FUTEX_OP_XOR:
- __futex_atomic_op("xor %1,%0,%1\n", ret, oldval, uaddr, oparg);
+ __futex_atomic_op("xor %1,%0,%4\n", ret, oldval, uaddr, oparg);
break;
default:
ret = -ENOSYS;
--
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