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Message-ID: <202210281501.29D9A905@keescook>
Date: Fri, 28 Oct 2022 15:03:04 -0700
From: Kees Cook <keescook@...omium.org>
To: kernel test robot <lkp@...el.com>
Cc: kbuild-all@...ts.01.org, linux-kernel@...r.kernel.org
Subject: Re: include/linux/fortify-string.h:220:25: warning: call to
'__write_overflow_field' declared with attribute warning: detected write
beyond size of field (1st parameter); maybe use struct_group()?
On Sun, Oct 23, 2022 at 04:45:58AM +0800, kernel test robot wrote:
> tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head: 4da34b7d175dc99b8befebd69e96546c960d526c
> commit: 28e77cc1c0686621a4d416f599cee5ab369daa0a fortify: Detect struct member overflows in memset() at compile-time
> date: 8 months ago
> config: arm-randconfig-r012-20221023
> compiler: arm-linux-gnueabi-gcc (GCC) 12.1.0
> reproduce (this is a W=1 build):
> wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> chmod +x ~/bin/make.cross
> # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=28e77cc1c0686621a4d416f599cee5ab369daa0a
> git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> git fetch --no-tags linus master
> git checkout 28e77cc1c0686621a4d416f599cee5ab369daa0a
> # save the config file
> mkdir build_dir && cp config build_dir/.config
> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=arm SHELL=/bin/bash fs/ocfs2/
>
> If you fix the issue, kindly add following tag where applicable
> | Reported-by: kernel test robot <lkp@...el.com>
>
> All warnings (new ones prefixed by >>):
>
> In file included from include/linux/string.h:253,
> from include/linux/bitmap.h:11,
> from include/linux/cpumask.h:12,
> from include/linux/smp.h:13,
> from include/linux/lockdep.h:14,
> from include/linux/spinlock.h:62,
> from include/linux/mmzone.h:8,
> from include/linux/gfp.h:6,
> from include/linux/slab.h:15,
> from fs/ocfs2/dlmglue.c:11:
> In function 'fortify_memset_chk',
> inlined from 'ocfs2_lock_res_free' at fs/ocfs2/dlmglue.c:790:2:
> >> include/linux/fortify-string.h:220:25: warning: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Wattribute-warning]
> 220 | __write_overflow_field(p_size_field, size);
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This appears to be a compiler bug. The line in question is:
memset(&res->l_lksb, 0, sizeof(res->l_lksb));
Looking at binary output, something is failing in dead code elimination,
as the copy of the code holding this is never called, and has a
non-literal value for the __builtin_object_size() output, which isn't
possible.
-Kees
--
Kees Cook
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