linux-kernel - [ 22/68] alpha: fix 32/64-bit bug in futex support

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Message-Id: <20120309190216.741029698@linuxfoundation.org>
Date:	Fri, 09 Mar 2012 11:02:36 -0800
From:	Greg KH <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Michael Cree <mcree@...on.net.nz>,
	Phil Carmody <ext-phil.2.carmody@...ia.com>,
	Richard Henderson <rth@...ddle.net>,
	Michel Lespinasse <walken@...gle.com>,
	Ivan Kokshaysky <ink@...assic.park.msu.ru>,
	Matt Turner <mattst88@...il.com>
Subject: [ 22/68] alpha: fix 32/64-bit bug in futex support

3.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andrew Morton <akpm@...ux-foundation.org>

commit 62aca403657fe30e5235c5331e9871e676d9ea0a upstream.

Michael Cree said:

: : I have noticed some user space problems (pulseaudio crashes in pthread
: : code, glibc/nptl test suite failures, java compiler freezes on SMP alpha
: : systems) that arise when using a 2.6.39 or later kernel on Alpha.
: : Bisecting between 2.6.38 and 2.6.39 (using glibc/nptl test suite as
: : criterion for good/bad kernel) eventually leads to:
: :
: : 8d7718aa082aaf30a0b4989e1f04858952f941bc is the first bad commit
: : commit 8d7718aa082aaf30a0b4989e1f04858952f941bc
: : Author: Michel Lespinasse <walken@...gle.com>
: : Date:   Thu Mar 10 18:50:58 2011 -0800
: :
: :     futex: Sanitize futex ops argument types
: :
: :     Change futex_atomic_op_inuser and futex_atomic_cmpxchg_inatomic
: :     prototypes to use u32 types for the futex as this is the data type the
: :     futex core code uses all over the place.
: :
: : Looking at the commit I see there is a change of the uaddr argument in
: : the Alpha architecture specific code for futexes from int to u32, but I
: : don't see why this should cause a problem.

Richard Henderson said:

: futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
:                               u32 oldval, u32 newval)
: ...
:         :       "r"(uaddr), "r"((long)oldval), "r"(newval)
:
:
: There is no 32-bit compare instruction.  These are implemented by
: consistently extending the values to a 64-bit type.  Since the
: load instruction sign-extends, we want to sign-extend the other
: quantity as well (despite the fact it's logically unsigned).
:
: So:
:
: -        :       "r"(uaddr), "r"((long)oldval), "r"(newval)
: +        :       "r"(uaddr), "r"((long)(int)oldval), "r"(newval)
:
: should do the trick.

Michael said:

: This fixes the glibc test suite failures and the pulseaudio related
: crashes, but it does not fix the java compiiler lockups that I was (and
: are still) observing.  That is some other problem.

Reported-by: Michael Cree <mcree@...on.net.nz>
Tested-by: Michael Cree <mcree@...on.net.nz>
Acked-by: Phil Carmody <ext-phil.2.carmody@...ia.com>
Cc: Richard Henderson <rth@...ddle.net>
Cc: Michel Lespinasse <walken@...gle.com>
Cc: Ivan Kokshaysky <ink@...assic.park.msu.ru>
Reviewed-by: Matt Turner <mattst88@...il.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/alpha/include/asm/futex.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/alpha/include/asm/futex.h
+++ b/arch/alpha/include/asm/futex.h
@@ -108,7 +108,7 @@ futex_atomic_cmpxchg_inatomic(u32 *uval,
 	"	lda	$31,3b-2b(%0)\n"
 	"	.previous\n"
 	:	"+r"(ret), "=&r"(prev), "=&r"(cmp)
-	:	"r"(uaddr), "r"((long)oldval), "r"(newval)
+	:	"r"(uaddr), "r"((long)(int)oldval), "r"(newval)
 	:	"memory");

 	*uval = prev;

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