Messages in this thread | | | From | Mathieu Malaterre <> | Date | Mon, 26 Feb 2018 18:50:11 +0100 | Subject | Re: [PATCH 06/21] powerpc: Avoid comparison of unsigned long >= 0 in __access_ok |
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On Mon, Feb 26, 2018 at 8:44 AM, Mathieu Malaterre <malat@debian.org> wrote: > On Mon, Feb 26, 2018 at 7:50 AM, Christophe LEROY > <christophe.leroy@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 <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))))) >>> >>> >>> 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:
Tested again today with gcc 6.3.0 and gcc is still producing the original warning (treated as error).
>> 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.
So the other alternative is to update a bunch of ppc32 defconfig(s) with: CONFIG_PPC_DISABLE_WERROR=y.
Would that be preferable ?
>> Christophe >> >> >>> >>> Christophe >>> >>>> #endif >>>> >>
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