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    Subject[12/27] x86: Fix mmap random address range
    2.6.32-longterm review patch.  If anyone has any objections, please let me know.

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

    From: Ludwig Nussel <ludwig.nussel@suse.de>

    commit 9af0c7a6fa860698d080481f24a342ba74b68982 upstream.

    On x86_32 casting the unsigned int result of get_random_int() to
    long may result in a negative value. On x86_32 the range of
    mmap_rnd() therefore was -255 to 255. The 32bit mode on x86_64
    used 0 to 255 as intended.

    The bug was introduced by 675a081 ("x86: unify mmap_{32|64}.c")
    in January 2008.

    Signed-off-by: Ludwig Nussel <ludwig.nussel@suse.de>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: harvey.harrison@gmail.com
    Cc: "H. Peter Anvin" <hpa@zytor.com>
    Cc: Harvey Harrison <harvey.harrison@gmail.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Link: http://lkml.kernel.org/r/201111152246.pAFMklOB028527@wpaz5.hot.corp.google.com
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    arch/x86/mm/mmap.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    --- a/arch/x86/mm/mmap.c
    +++ b/arch/x86/mm/mmap.c
    @@ -87,9 +87,9 @@ static unsigned long mmap_rnd(void)
    */
    if (current->flags & PF_RANDOMIZE) {
    if (mmap_is_ia32())
    - rnd = (long)get_random_int() % (1<<8);
    + rnd = get_random_int() % (1<<8);
    else
    - rnd = (long)(get_random_int() % (1<<28));
    + rnd = get_random_int() % (1<<28);
    }
    return rnd << PAGE_SHIFT;
    }



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