[linux-next:master 3417/14198] drivers/misc/lkdtm/cfi.c:100:27: sparse: sparse: Using plain integer as NULL pointer

[kernel test robot <lkp@xxxxxxxxx>]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
head:   d3fde8ff50ab265749704bd7fbcf70d35235421f
commit: 2e53b877dc1258d4ac3de98f496bb88ec3bf5e25 [3417/14198] lkdtm: Add CFI_BACKWARD to test ROP mitigations
config: arc-randconfig-s031-20220527 (https://download.01.org/0day-ci/archive/20220528/202205281038.F1GyW2IY-lkp@xxxxxxxxx/config)
compiler: arceb-elf-gcc (GCC) 11.3.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # apt-get install sparse
        # sparse version: v0.6.4-14-g5a0004b5-dirty
        # https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=2e53b877dc1258d4ac3de98f496bb88ec3bf5e25
        git remote add linux-next https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
        git fetch --no-tags linux-next master
        git checkout 2e53b877dc1258d4ac3de98f496bb88ec3bf5e25
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.3.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=arc SHELL=/bin/bash drivers/misc/lkdtm/

If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@xxxxxxxxx>


sparse warnings: (new ones prefixed by >>)
>> drivers/misc/lkdtm/cfi.c:100:27: sparse: sparse: Using plain integer as NULL pointer
   drivers/misc/lkdtm/cfi.c:72:13: sparse: sparse: non size-preserving pointer to integer cast
   drivers/misc/lkdtm/cfi.c:72:13: sparse: sparse: non size-preserving integer to pointer cast
   drivers/misc/lkdtm/cfi.c:87:13: sparse: sparse: non size-preserving pointer to integer cast
   drivers/misc/lkdtm/cfi.c:87:13: sparse: sparse: non size-preserving integer to pointer cast

vim +100 drivers/misc/lkdtm/cfi.c

    96	
    97	static void lkdtm_CFI_BACKWARD(void)
    98	{
    99		/* Use calculated gotos to keep labels addressable. */
 > 100		void *labels[] = {0, &&normal, &&redirected, &&check_normal, &&check_redirected};
   101	
   102		pr_info("Attempting unchecked stack return address redirection ...\n");
   103	
   104		/* Always false */
   105		if (force_check) {
   106			/*
   107			 * Prepare to call with NULLs to avoid parameters being treated as
   108			 * constants in -02.
   109			 */
   110			set_return_addr_unchecked(NULL, NULL);
   111			set_return_addr(NULL, NULL);
   112			if (force_check)
   113				goto *labels[1];
   114			if (force_check)
   115				goto *labels[2];
   116			if (force_check)
   117				goto *labels[3];
   118			if (force_check)
   119				goto *labels[4];
   120			return;
   121		}
   122	
   123		/*
   124		 * Use fallthrough switch case to keep basic block ordering between
   125		 * set_return_addr*() and the label after it.
   126		 */
   127		switch (force_check) {
   128		case 0:
   129			set_return_addr_unchecked(&&normal, &&redirected);
   130			fallthrough;
   131		case 1:
   132	normal:
   133			/* Always true */
   134			if (!force_check) {
   135				pr_err("FAIL: stack return address manipulation failed!\n");
   136				/* If we can't redirect "normally", we can't test mitigations. */
   137				return;
   138			}
   139			break;
   140		default:
   141	redirected:
   142			pr_info("ok: redirected stack return address.\n");
   143			break;
   144		}
   145	
   146		pr_info("Attempting checked stack return address redirection ...\n");
   147	
   148		switch (force_check) {
   149		case 0:
   150			set_return_addr(&&check_normal, &&check_redirected);
   151			fallthrough;
   152		case 1:
   153	check_normal:
   154			/* Always true */
   155			if (!force_check) {
   156				pr_info("ok: control flow unchanged.\n");
   157				return;
   158			}
   159	
   160	check_redirected:
   161			pr_err("FAIL: stack return address was redirected!\n");
   162			break;
   163		}
   164	
   165		if (IS_ENABLED(CONFIG_ARM64_PTR_AUTH_KERNEL)) {
   166			pr_expected_config(CONFIG_ARM64_PTR_AUTH_KERNEL);
   167			return;
   168		}
   169		if (IS_ENABLED(CONFIG_SHADOW_CALL_STACK)) {
   170			pr_expected_config(CONFIG_SHADOW_CALL_STACK);
   171			return;
   172		}
   173		pr_warn("This is probably expected, since this %s was built *without* %s=y nor %s=y\n",
   174			lkdtm_kernel_info,
   175			"CONFIG_ARM64_PTR_AUTH_KERNEL", "CONFIG_SHADOW_CALL_STACK");
   176	}
   177	

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