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

[kernel test robot <lkp@intel.com>]

[-- Attachment #1: Type: text/plain, Size: 2793 bytes --]

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.


vim +52 fs/sysfs/file.c

    35	
    36	/*
    37	 * To be proactively defensive against sysfs show() handlers that do not
    38	 * correctly stay within their PAGE_SIZE buffer, use the vmap area to gain
    39	 * the trailing guard page which will stop linear buffer overflows.
    40	 */
    41	static void *sysfs_kf_seq_start(struct seq_file *sf, loff_t *ppos)
    42	{
    43		struct kernfs_open_file *of = sf->private;
    44		struct kernfs_node *kn = of->kn;
    45	
    46		WARN_ON_ONCE(sf->buf);
    47		sf->buf = __vmalloc(kn->attr.size, GFP_KERNEL_ACCOUNT);
    48		if (!sf->buf)
    49			return ERR_PTR(-ENOMEM);
    50		sf->size = kn->attr.size;
    51	
  > 52		return NULL + !*ppos;
    53	}
    54	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 35632 bytes --]