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    Subject[PATCH 06/21] powerpc: Avoid comparison of unsigned long >= 0 in __access_ok
    Date
    Rewrite check size - 1 <= Y as size < Y since `size` is unsigned value.
    Fix warning (treated as error in W=1):

    CC arch/powerpc/kernel/signal_32.o
    In file included from ./include/linux/uaccess.h:14:0,
    from ./include/asm-generic/termios-base.h:8,
    from ./arch/powerpc/include/asm/termios.h:20,
    from ./include/uapi/linux/termios.h:6,
    from ./include/linux/tty.h:7,
    from arch/powerpc/kernel/signal_32.c:36:
    ./include/asm-generic/termios-base.h: In function ‘user_termio_to_kernel_termios’:
    ./arch/powerpc/include/asm/uaccess.h:52:35: error: comparison of unsigned expression >= 0 is always true [-Werror=type-limits]
    (((size) == 0) || (((size) - 1) <= ((segment).seg - (addr)))))
    ^
    ./arch/powerpc/include/asm/uaccess.h:58:3: note: in expansion of macro ‘__access_ok’
    __access_ok((__force unsigned long)(addr), (size), get_fs()))
    ^~~~~~~~~~~
    ./arch/powerpc/include/asm/uaccess.h:262:6: note: in expansion of macro ‘access_ok’
    if (access_ok(VERIFY_READ, __gu_addr, (size))) \
    ^~~~~~~~~
    ./arch/powerpc/include/asm/uaccess.h:80:2: note: in expansion of macro ‘__get_user_check’
    __get_user_check((x), (ptr), sizeof(*(ptr)))
    ^~~~~~~~~~~~~~~~
    ./include/asm-generic/termios-base.h:36:6: note: in expansion of macro ‘get_user’
    if (get_user(termios->c_line, &termio->c_line) < 0)
    ^~~~~~~~
    [...]
    cc1: all warnings being treated as errors

    Signed-off-by: Mathieu Malaterre <malat@debian.org>
    ---
    arch/powerpc/include/asm/uaccess.h | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
    index 51bfeb8777f0..fadc406bd39d 100644
    --- a/arch/powerpc/include/asm/uaccess.h
    +++ b/arch/powerpc/include/asm/uaccess.h
    @@ -49,7 +49,7 @@

    #define __access_ok(addr, size, segment) \
    (((addr) <= (segment).seg) && \
    - (((size) == 0) || (((size) - 1) <= ((segment).seg - (addr)))))
    + (((size) == 0) || ((size) < ((segment).seg - (addr)))))

    #endif

    --
    2.11.0
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