linux-kernel - Re: kisskb: FAILED linux-next/m68k-allmodconfig/m68k-gcc8 Tue Jan 25, 18:24

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Date:   Wed, 26 Jan 2022 00:53:59 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Yury Norov <yury.norov@...il.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>
CC:     linux-m68k <linux-m68k@...ts.linux-m68k.org>,
        Arnd Bergmann <arnd@...db.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: kisskb: FAILED linux-next/m68k-allmodconfig/m68k-gcc8 Tue Jan 25, 18:24



On January 25, 2022 10:02:56 AM PST, Yury Norov <yury.norov@...il.com> wrote:
>On Tue, Jan 25, 2022 at 12:47 AM Geert Uytterhoeven
><geert@...ux-m68k.org> wrote:
>>
>> On Tue, Jan 25, 2022 at 8:31 AM <noreply@...erman.id.au> wrote:
>> > FAILED linux-next/m68k-allmodconfig/m68k-gcc8 Tue Jan 25, 18:24
>> >
>> > http://kisskb.ellerman.id.au/kisskb/buildresult/14688953/
>> >
>> > Commit:   Add linux-next specific files for 20220125
>> >           d25ee88530253138d0b20d43511ca5acbda4e9f7
>> > Compiler: m68k-linux-gcc (GCC) 8.1.0 / GNU ld (GNU Binutils) 2.30
>> >
>> > Possible errors
>> > ---------------
>> >
>> > arch/m68k/include/asm/bitops.h:329:20: error: array subscript 2 is above array bounds of 'long unsigned int[1]' [-Werror=array-bounds]
>
>The array-bounds warning has been enabled just recently. CC Kees Cook for this.
>
>> > cc1: all warnings being treated as errors
>> > make[4]: *** [scripts/Makefile.build:289: drivers/net/ipa/ipa_mem.o] Error 1
>> > make[3]: *** [scripts/Makefile.build:572: drivers/net/ipa] Error 2
>> > make[2]: *** [scripts/Makefile.build:572: drivers/net] Error 2
>> > make[1]: *** [Makefile:1965: drivers] Error 2
>> > make: *** [Makefile:226: __sub-make] Error 2
>> >
>> > No warnings found in log.
>>
>> The code that causes this is drivers/net/ipa/ipa_mem.c:ipa_mem_valid():
>>
>>         DECLARE_BITMAP(regions, IPA_MEM_COUNT) = { };
>>         ...
>>         for_each_clear_bit(mem_id, regions, IPA_MEM_COUNT) {
>>                 if (ipa_mem_id_required(ipa, mem_id))
>>                         dev_err(dev, "required memory region %u missing\n",
>>                                 mem_id);
>>         }
>>
>> This only happens with gcc-8, not with gcc-9, so it might be a
>> compiler bug. I don't see anything wrong with c:ipa_mem_valid()
>> nor with m68k's find_first_zero_bit().
>
>I don't see any problems about how this code uses bitmap API.
>The m68k version of find_first_zero_bit() looks correct as well.

The trouble is with "enum ipa_mem_id mem_id;" which is an int, and the bitmap API requires unsigned long. I tried to fix this[1] at the source, but the maintainers want each[2] call site to fix it instead. :(

Sorry I missed this case in my build testing! If no one beats me to it, I can send a patch tomorrow.

-Kees

[1] https://lore.kernel.org/lkml/20211203100846.3977195-1-keescook@chromium.org/
[2] https://lore.kernel.org/lkml/?q=f%3A%22Kees+Cook%22+%22Use+correctly+sized+arguments+for+bit+field%22

-- 
Kees Cook