Re: [PATCH v3] sysfs: Unconditionally use vmalloc for buffer

From: Kees Cook <keescook@chromium.org>
To: Nathan Chancellor <nathan@kernel.org>
Cc: kernel test robot <lkp@intel.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	kbuild-all@lists.01.org, clang-built-linux@googlegroups.com,
	Andrew Morton <akpm@linux-foundation.org>,
	Linux Memory Management List <linux-mm@kvack.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Michal Hocko <mhocko@suse.com>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	Lee Duncan <lduncan@suse.com>, Chris Leech <cleech@redhat.com>,
	Adam Nichols <adam@grimm-co.com>
Subject: Re: [PATCH v3] sysfs: Unconditionally use vmalloc for buffer
Date: Wed, 31 Mar 2021 23:59:03 -0700	[thread overview]
Message-ID: <202103312354.A15E2A808@keescook> (raw)
In-Reply-To: <20210401064753.6ub6dhcuu6zuhdjq@archlinux-ax161>

On Wed, Mar 31, 2021 at 11:47:53PM -0700, Nathan Chancellor wrote:
> On Thu, Apr 01, 2021 at 02:41:37PM +0800, kernel test robot wrote:
> > Hi Kees,
> > 
> > I love your patch! Perhaps something to improve:
> > 
> > [auto build test WARNING on driver-core/driver-core-testing]
> > [also build test WARNING on kees/for-next/pstore v5.12-rc5 next-20210331]
> > [cannot apply to hnaz-linux-mm/master]
> > [If your patch is applied to the wrong git tree, kindly drop us a note.
> > And when submitting patch, we suggest to use '--base' as documented in
> > https://git-scm.com/docs/git-format-patch]
> > 
> > url:    https://github.com/0day-ci/linux/commits/Kees-Cook/sysfs-Unconditionally-use-vmalloc-for-buffer/20210401-102455
> > base:   https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core.git d225ef6fda7ce9ff7d28764bd1cceea2d0215e8b
> > config: powerpc-randconfig-r001-20210401 (attached as .config)
> > compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 1c268a8ff4e90a85d0e634350b1104080614cf2b)
> > 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
> >         # install powerpc cross compiling tool for clang build
> >         # apt-get install binutils-powerpc-linux-gnu
> >         # https://github.com/0day-ci/linux/commit/c80ca56c15314908ebc1881678da3b36e007a2f4
> >         git remote add linux-review https://github.com/0day-ci/linux
> >         git fetch --no-tags linux-review Kees-Cook/sysfs-Unconditionally-use-vmalloc-for-buffer/20210401-102455
> >         git checkout c80ca56c15314908ebc1881678da3b36e007a2f4
> >         # save the attached .config to linux build tree
> >         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=powerpc 
> > 
> > If you fix the issue, kindly add following tag as appropriate
> > Reported-by: kernel test robot <lkp@intel.com>
> > 
> > All warnings (new ones prefixed by >>):
> > 
> > >> fs/sysfs/file.c:52:14: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
> >            return NULL + !*ppos;
> >                   ~~~~ ^
> >    1 warning generated.
> > 
> 
> Arnd addressed other warnings of this nature in this patch:
> 
> https://lore.kernel.org/r/20201028151202.3074398-1-arnd@kernel.org/

Ah! Yeah, I copied exactly that clever idiom that Arnd fixed. :)

> which it seems never got picked up :(

Greg, are you able to pick this up too? (Yeow, sent in October!)
(Or I could respin and send them as a series?)

-- 
Kees Cook