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    Subject[PATCH 3.17 245/319] lib/bitmap.c: fix undefined shift in __bitmap_shift_{left|right}()
    Date
    3.17-stable review patch.  If anyone has any objections, please let me know.

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

    From: Jan Kara <jack@suse.cz>

    commit ea5d05b34aca25c066e0699512d0ffbd8ee6ac3e upstream.

    If __bitmap_shift_left() or __bitmap_shift_right() are asked to shift by
    a multiple of BITS_PER_LONG, they will try to shift a long value by
    BITS_PER_LONG bits which is undefined. Change the functions to avoid
    the undefined shift.

    Coverity id: 1192175
    Coverity id: 1192174
    Signed-off-by: Jan Kara <jack@suse.cz>
    Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    lib/bitmap.c | 8 ++++++--
    1 file changed, 6 insertions(+), 2 deletions(-)

    --- a/lib/bitmap.c
    +++ b/lib/bitmap.c
    @@ -131,7 +131,9 @@ void __bitmap_shift_right(unsigned long
    lower = src[off + k];
    if (left && off + k == lim - 1)
    lower &= mask;
    - dst[k] = upper << (BITS_PER_LONG - rem) | lower >> rem;
    + dst[k] = lower >> rem;
    + if (rem)
    + dst[k] |= upper << (BITS_PER_LONG - rem);
    if (left && k == lim - 1)
    dst[k] &= mask;
    }
    @@ -172,7 +174,9 @@ void __bitmap_shift_left(unsigned long *
    upper = src[k];
    if (left && k == lim - 1)
    upper &= (1UL << left) - 1;
    - dst[k + off] = lower >> (BITS_PER_LONG - rem) | upper << rem;
    + dst[k + off] = upper << rem;
    + if (rem)
    + dst[k + off] |= lower >> (BITS_PER_LONG - rem);
    if (left && k + off == lim - 1)
    dst[k + off] &= (1UL << left) - 1;
    }



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