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    Subject[PATCH 3.16.y-ckt 027/168] bitops: Fix shift overflow in GENMASK macros
    Date
    3.16.7-ckt3 -stable review patch.  If anyone has any objections, please let me know.

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

    From: Maxime COQUELIN <maxime.coquelin@st.com>

    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@st.com>
    Suggested-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
    Signed-off-by: Maxime Coquelin <maxime.coquelin@st.com>
    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Cc: linux@rasmusvillemoes.dk
    Cc: gong.chen@linux.intel.com
    Cc: John Sullivan <jsrhbz@kanargh.force9.co.uk>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    Cc: Theodore Ts'o <tytso@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@kernel.org>
    Signed-off-by: Luis Henriques <luis.henriques@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 cbc5833fb221..38b5f5c88c18 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);
    --
    2.1.3


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