[3.13.y-ckt stable] Patch "bitops: Fix shift overflow in GENMASK macros" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    bitops: Fix shift overflow in GENMASK macros

to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11-ckt12.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 449ad906d6ecf522b153f48f37fd9ef6d4e03553 Mon Sep 17 00:00:00 2001
From: Maxime COQUELIN <maxime.coquelin at st.com>
Date: Thu, 6 Nov 2014 10:54:19 +0100
Subject: bitops: Fix shift overflow in GENMASK macros

commit 00b4d9a14125f1e51874def2b9de6092e007412d upstream.

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 at st.com>
Suggested-by: Rasmus Villemoes <linux at rasmusvillemoes.dk>
Signed-off-by: Maxime Coquelin <maxime.coquelin at st.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz at infradead.org>
Cc: linux at rasmusvillemoes.dk
Cc: gong.chen at linux.intel.com
Cc: John Sullivan <jsrhbz at kanargh.force9.co.uk>
Cc: Linus Torvalds <torvalds at linux-foundation.org>
Cc: Paul E. McKenney <paulmck at linux.vnet.ibm.com>
Cc: Theodore Ts'o <tytso at mit.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 at kernel.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 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);
--
1.9.1