linux-kernel - [tip:core/urgent] bitops: Fix shift overflow in GENMASK macros

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Message-ID: <tip-00b4d9a14125f1e51874def2b9de6092e007412d@git.kernel.org>
Date:	Sun, 16 Nov 2014 01:49:59 -0800
From:	tip-bot for Maxime COQUELIN <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	paulmck@...ux.vnet.ibm.com, hpa@...or.com,
	linux-kernel@...r.kernel.org, eric.paire@...com,
	peterz@...radead.org, torvalds@...ux-foundation.org,
	mingo@...nel.org, linux@...musvillemoes.dk, tytso@....edu,
	jsrhbz@...argh.force9.co.uk, maxime.coquelin@...com,
	tglx@...utronix.de
Subject: [tip:core/urgent] bitops: Fix shift overflow in GENMASK macros

Commit-ID:  00b4d9a14125f1e51874def2b9de6092e007412d
Gitweb:     http://git.kernel.org/tip/00b4d9a14125f1e51874def2b9de6092e007412d
Author:     Maxime COQUELIN <maxime.coquelin@...com>
AuthorDate: Thu, 6 Nov 2014 10:54:19 +0100
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Sun, 16 Nov 2014 09:55:39 +0100

bitops: Fix shift overflow in GENMASK macros

On some 32 bits architectures, including x86, GENMASK(31, 0) returns 0
instead of the expected ~0UL.

This is the same on some 64 bits architectures with GENMASK_ULL(63, 0).

This is due to an overflow in the shift operand, 1 << 32 for GENMASK,
1 << 64 for GENMASK_ULL.

Reported-by: Eric Paire <eric.paire@...com>
Suggested-by: Rasmus Villemoes <linux@...musvillemoes.dk>
Signed-off-by: Maxime Coquelin <maxime.coquelin@...com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: <stable@...r.kernel.org> # v3.13+
Cc: linux@...musvillemoes.dk
Cc: gong.chen@...ux.intel.com
Cc: John Sullivan <jsrhbz@...argh.force9.co.uk>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Cc: Theodore Ts'o <tytso@....edu>
Fixes: 10ef6b0dffe4 ("bitops: Introduce a more generic BITMASK macro")
Link: http://lkml.kernel.org/r/1415267659-10563-1-git-send-email-maxime.coquelin@st.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 include/linux/bitops.h | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index be5fd38..5d858e0 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -18,8 +18,11 @@
  * position @h. For example
  * GENMASK_ULL(39, 21) gives us the 64bit vector 0x000000ffffe00000.
  */
-#define GENMASK(h, l)		(((U32_C(1) << ((h) - (l) + 1)) - 1) << (l))
-#define GENMASK_ULL(h, l)	(((U64_C(1) << ((h) - (l) + 1)) - 1) << (l))
+#define GENMASK(h, l) \
+	(((~0UL) << (l)) & (~0UL >> (BITS_PER_LONG - 1 - (h))))
+
+#define GENMASK_ULL(h, l) \
+	(((~0ULL) << (l)) & (~0ULL >> (BITS_PER_LONG_LONG - 1 - (h))))
 
 extern unsigned int __sw_hweight8(unsigned int w);
 extern unsigned int __sw_hweight16(unsigned int w);
--
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