linux-kernel - Re: [PATCH] string.h: work around __builtin_constant

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Message-ID: <CAK8P3a1MW3+d6MpKWbziTe+jvbmwmXQqG6Tv-N0BnrJ1uLQN4g@mail.gmail.com>
Date:   Mon, 7 Aug 2017 22:29:21 +0000
From:   Arnd Bergmann <arnd@...db.de>
To:     Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Daniel Micay <danielmicay@...il.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Dan Williams <dan.j.williams@...el.com>,
        David Howells <dhowells@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] string.h: work around __builtin_constant_p quirk

On Mon, Aug 7, 2017 at 11:15 AM, Arnd Bergmann <arnd@...db.de> wrote:
> The compile-time check in the hardened memcpy() triggered a build
> error in code that should not have:
>
> In function 'memcpy',
>     inlined from '__adfs_dir_put' at fs/adfs/dir_f.c:318:2,
>     inlined from 'adfs_f_update' at fs/adfs/dir_f.c:403:2:
> include/linux/string.h:305:4: error: call to '__read_overflow2' declared with attribute error: detected read beyond size of object passed as 2nd parameter
>     __read_overflow2();
>     ^~~~~~~~~~~~~~~~~~
>
> Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=72785
> Fixes: mmotm ("fortify: use WARN instead of BUG for now")
> Fixes: 6974f0c4555e ("include/linux/string.h: add the option of fortified string.h functions")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Please ignore this version for now, it seems that I accidentally
disabled all the compile-time
checks with the __builtin_choose_expr

       Arnd