On Mon, Feb 26, 2018 at 7:50 AM, Christophe LEROY <christophe.le...@c-s.fr> wrote: > > > Le 26/02/2018 à 07:34, Christophe LEROY a écrit : >> >> >> >> Le 25/02/2018 à 18:22, Mathieu Malaterre a écrit : >>> >>> 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 <ma...@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))))) >> >> >> IIUC, ((2 - 1) <= 1) is the same as (2 < 1) ????? >
The whole series was pretty mediocre, but this one was actually pretty destructive. Thanks for catching this. > > Note that I already try to submit a fix for this warning 3 years ago > (https://patchwork.ozlabs.org/patch/418075/) and it was rejected with the > following comment: > > Again, I don't think Linux enables this warning. What did you do to > produce this? In any case, it's a bad warning that doesn't take macros > into account, and the answer is not to make the code less clear by hiding > the fact that zero is a special case. Right. I'll try to see how to make W=1 run without error with an alternate solution. > Christophe > > >> >> Christophe >> >>> #endif >>> >