Re: [PATCH RFC v2] tpm: tpm_vtpm_proxy: do not reference kernel memory as user memory

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

Hi Jarkko,

[This is a private test report for your RFC patch.]
kernel test robot noticed the following build warnings:

[auto build test WARNING on char-misc/char-misc-testing]
[also build test WARNING on char-misc/char-misc-next char-misc/char-misc-linus linus/master v6.4-rc4 next-20230530]
[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#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Jarkko-Sakkinen/tpm-tpm_vtpm_proxy-do-not-reference-kernel-memory-as-user-memory/20230530-100537
base:   char-misc/char-misc-testing
patch link:    https://lore.kernel.org/r/20230530020133.235765-1-jarkko%40kernel.org
patch subject: [PATCH RFC v2] tpm: tpm_vtpm_proxy: do not reference kernel memory as user memory
config: arm64-randconfig-r034-20230530 (https://download.01.org/0day-ci/archive/20230530/202305301907.KVm9YudP-lkp@intel.com/config)
compiler: clang version 17.0.0 (https://github.com/llvm/llvm-project 4faf3aaf28226a4e950c103a14f6fc1d1fdabb1b)
reproduce (this is a W=1 build):
        mkdir -p ~/bin
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install arm64 cross compiling tool for clang build
        # apt-get install binutils-aarch64-linux-gnu
        # https://github.com/intel-lab-lkp/linux/commit/919bd177830a9508a5a67fc17014cd10047d8c2f
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Jarkko-Sakkinen/tpm-tpm_vtpm_proxy-do-not-reference-kernel-memory-as-user-memory/20230530-100537
        git checkout 919bd177830a9508a5a67fc17014cd10047d8c2f
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang ~/bin/make.cross W=1 O=build_dir ARCH=arm64 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang ~/bin/make.cross W=1 O=build_dir ARCH=arm64 SHELL=/bin/bash drivers/char/tpm/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202305301907.KVm9YudP-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from drivers/char/tpm/tpm_vtpm_proxy.c:24:
   In file included from drivers/char/tpm/tpm.h:28:
   include/linux/tpm_eventlog.h:167:6: warning: variable 'mapping_size' set but not used [-Wunused-but-set-variable]
           int mapping_size;
               ^
>> drivers/char/tpm/tpm_vtpm_proxy.c:77:6: warning: variable 'rc' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
           if (buf)
               ^~~
   drivers/char/tpm/tpm_vtpm_proxy.c:83:7: note: uninitialized use occurs here
           if (!rc)
                ^~
   drivers/char/tpm/tpm_vtpm_proxy.c:77:2: note: remove the 'if' if its condition is always true
           if (buf)
           ^~~~~~~~
   drivers/char/tpm/tpm_vtpm_proxy.c:64:8: note: initialize the variable 'rc' to silence this warning
           int rc;
                 ^
                  = 0
   2 warnings generated.


vim +77 drivers/char/tpm/tpm_vtpm_proxy.c

    55	
    56	/*
    57	 * Functions related to 'server side'
    58	 */
    59	
    60	static ssize_t __vtpm_proxy_read_unlocked(struct proxy_dev *proxy_dev, char __user *buf,
    61						  size_t count)
    62	{
    63		size_t len;
    64		int rc;
    65	
    66		if (!(proxy_dev->state & STATE_OPENED_FLAG))
    67			return -EPIPE;
    68	
    69		len = proxy_dev->req_len;
    70	
    71		if (count < len || len > sizeof(proxy_dev->buffer)) {
    72			pr_debug("Invalid size in recv: count=%zd, req_len=%zd\n",
    73				 count, len);
    74			return -EIO;
    75		}
    76	
  > 77		if (buf)
    78			rc = copy_to_user(buf, proxy_dev->buffer, len);
    79	
    80		memset(proxy_dev->buffer, 0, len);
    81		proxy_dev->req_len = 0;
    82	
    83		if (!rc)
    84			proxy_dev->state |= STATE_WAIT_RESPONSE_FLAG;
    85	
    86		if (rc)
    87			return -EFAULT;
    88	
    89		return len;
    90	}
    91	

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https://github.com/intel/lkp-tests/wiki