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    Subject[ 02/46] s390/compat: fix mmap compat system calls
    Date
    From: Greg KH <gregkh@linuxfoundation.org>

    3.5-stable review patch. If anyone has any objections, please let me know.

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

    From: Heiko Carstens <heiko.carstens@de.ibm.com>

    commit e85871218513c54f7dfdb6009043cb638f2fecbe upstream.

    The native 31 bit and the compat behaviour for the mmap system calls differ:

    In native 31 bit mode the passed in address for the mmap system call will be
    unmodified passed to sys_mmap_pgoff().
    In compat mode however the passed in address will be modified with
    compat_ptr() which masks out the most significant bit.

    The result is that in native 31 bit mode each mmap request (with MAP_FIXED)
    will fail where the most significat bit is set, while in compat mode it
    may succeed.

    This odd behaviour was introduced with d3815898 "[S390] mmap: add missing
    compat_ptr conversion to both mmap compat syscalls".

    To restore a consistent behaviour accross native and compat mode this
    patch functionally reverts the above mentioned commit.

    Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
    Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/s390/kernel/compat_linux.c | 2 --
    1 file changed, 2 deletions(-)

    --- a/arch/s390/kernel/compat_linux.c
    +++ b/arch/s390/kernel/compat_linux.c
    @@ -622,7 +622,6 @@ asmlinkage unsigned long old32_mmap(stru
    return -EFAULT;
    if (a.offset & ~PAGE_MASK)
    return -EINVAL;
    - a.addr = (unsigned long) compat_ptr(a.addr);
    return sys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
    a.offset >> PAGE_SHIFT);
    }
    @@ -633,7 +632,6 @@ asmlinkage long sys32_mmap2(struct mmap_

    if (copy_from_user(&a, arg, sizeof(a)))
    return -EFAULT;
    - a.addr = (unsigned long) compat_ptr(a.addr);
    return sys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd, a.offset);
    }




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