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    Subject[PATCH 4.9 134/177] mm: Handle 0 flags in _calc_vm_trans() macro
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

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

    From: Jan Kara <jack@suse.cz>


    [ Upstream commit 592e254502041f953e84d091eae2c68cba04c10b ]

    _calc_vm_trans() does not handle the situation when some of the passed
    flags are 0 (which can happen if these VM flags do not make sense for
    the architecture). Improve the _calc_vm_trans() macro to return 0 in
    such situation. Since all passed flags are constant, this does not add
    any runtime overhead.

    Signed-off-by: Jan Kara <jack@suse.cz>
    Signed-off-by: Dan Williams <dan.j.williams@intel.com>
    Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    include/linux/mman.h | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    --- a/include/linux/mman.h
    +++ b/include/linux/mman.h
    @@ -63,8 +63,9 @@ static inline bool arch_validate_prot(un
    * ("bit1" and "bit2" must be single bits)
    */
    #define _calc_vm_trans(x, bit1, bit2) \
    + ((!(bit1) || !(bit2)) ? 0 : \
    ((bit1) <= (bit2) ? ((x) & (bit1)) * ((bit2) / (bit1)) \
    - : ((x) & (bit1)) / ((bit1) / (bit2)))
    + : ((x) & (bit1)) / ((bit1) / (bit2))))

    /*
    * Combine the mmap "prot" argument into "vm_flags" used internally.

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