Re: [PATCH] fs/proc: add mask_secrets to prevent sensitive information leakage.

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

Hi zhanglin,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on linux/master]
[also build test WARNING on akpm-mm/mm-everything hnaz-mm/master linus/master v5.18-rc6 next-20220506]
[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/intel-lab-lkp/linux/commits/zhanglin/fs-proc-add-mask_secrets-to-prevent-sensitive-information-leakage/20220509-140823
base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c5eb0a61238dd6faf37f58c9ce61c9980aaffd7a
config: arc-allyesconfig (https://download.01.org/0day-ci/archive/20220509/202205091652.nHbogdH5-lkp@intel.com/config)
compiler: arceb-elf-gcc (GCC) 11.3.0
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://github.com/intel-lab-lkp/linux/commit/f8d1c429178d1ee0c447ee68f4e7b602c5df911f
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review zhanglin/fs-proc-add-mask_secrets-to-prevent-sensitive-information-leakage/20220509-140823
        git checkout f8d1c429178d1ee0c447ee68f4e7b602c5df911f
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.3.0 make.cross W=1 O=build_dir ARCH=arc SHELL=/bin/bash fs/proc/

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/proc/mask_secrets.c:49:8: warning: no previous prototype for 'mask_secrets' [-Wmissing-prototypes]
      49 | size_t mask_secrets(struct mm_struct *mm, char __user *buf,
         |        ^~~~~~~~~~~~
   fs/proc/mask_secrets.c: In function 'mask_secrets':
>> fs/proc/mask_secrets.c:71:13: warning: variable 'err' set but not used [-Wunused-but-set-variable]
      71 |         int err = 0;
         |             ^~~


vim +/mask_secrets +49 fs/proc/mask_secrets.c

    48	
  > 49	size_t mask_secrets(struct mm_struct *mm, char __user *buf,
    50				      size_t count, loff_t pos)
    51	{
    52		unsigned long arg_start = 0;
    53		unsigned long arg_end = 0;
    54		int mask_arg_len = 0;
    55		size_t remote_vm_copied = 0;
    56		struct file *file = 0;
    57		struct inode *inode = 0;
    58		char *kbuf = 0;
    59		char *progname = 0;
    60		int proghash = -1;
    61		int prog_found = 0;
    62		char *mask_arg_start = 0;
    63		char *mask_arg_end = 0;
    64		struct cmdline_hashtab_item *chi = 0;
    65		char *psecret = 0;
    66		size_t psecret_len = 0;
    67		char *pmask = 0;
    68		size_t pmask_len = 0;
    69		size_t size;
    70		size_t total_copied = 0;
  > 71		int err = 0;
    72	
    73		if (!is_mask_secrets_enabled()) {
    74			err = -EPERM;
    75			goto exit_err;
    76		}
    77	
    78		spin_lock(&mm->arg_lock);
    79		arg_start = mm->arg_start;
    80		arg_end = mm->arg_end;
    81		spin_unlock(&mm->arg_lock);
    82		if (arg_start >= arg_end) {
    83			err = -ERANGE;
    84			goto exit_err;
    85		}
    86		mask_arg_len = arg_end - arg_start + 1;
    87	
    88		file = get_mm_exe_file(mm);
    89		if (!file) {
    90			err = -ENOENT;
    91			goto exit_err;
    92		}
    93		inode = file_inode(file);
    94		if (!inode) {
    95			err = -ENOENT;
    96			goto exit_err;
    97		}
    98		proghash = cmdline_hash(inode->i_ino);
    99		kbuf = kzalloc(max(PATH_MAX, mask_arg_len), GFP_KERNEL);
   100		if (!kbuf) {
   101			err = -ENOMEM;
   102			goto exit_err;
   103		}
   104		progname = d_path(&file->f_path, kbuf, PATH_MAX);
   105		if (IS_ERR_OR_NULL(progname)) {
   106			err = -ENOENT;
   107			goto cleanup_kbuf;
   108		}
   109	
   110		rcu_read_lock();
   111		prog_found = 0;
   112		hash_for_each_possible_rcu(cmdline_hashtab, chi, hlist, proghash)
   113			if (strcmp(chi->progname, progname) == 0) {
   114				prog_found = 1;
   115				break;
   116			}
   117	
   118		if (!prog_found) {
   119			rcu_read_unlock();
   120			goto cleanup_kbuf;
   121		}
   122	
   123		mask_arg_start = kbuf;
   124		mask_arg_end = mask_arg_start + (arg_end - arg_start);
   125		remote_vm_copied = access_remote_vm(mm, arg_start, mask_arg_start, mask_arg_len, FOLL_ANON);
   126		if (remote_vm_copied <= 0) {
   127			rcu_read_unlock();
   128			err = -EIO;
   129			goto cleanup_kbuf;
   130		}
   131		/*skip progname */
   132		for (pmask = mask_arg_start; *pmask && (pmask <= mask_arg_end); pmask++)
   133			;
   134	
   135		if (!chi->secrets) {
   136			rcu_read_unlock();
   137			/*mask everything, such as: xxxconnect host port username password.*/
   138			for (pmask = pmask + 1; (pmask <= mask_arg_end); pmask++)
   139				for (; (pmask <= mask_arg_end) && (*pmask); pmask++)
   140					*pmask = 'Z';
   141			goto copydata;
   142		}
   143	
   144		for (pmask = pmask + 1; pmask <= mask_arg_end; pmask++) {
   145			psecret = chi->secrets;
   146			while (*psecret) {
   147				psecret_len = strlen(psecret);
   148				if (psecret_len < 2) {
   149					rcu_read_unlock();
   150					err = -EINVAL;
   151					goto cleanup_kbuf;
   152				}
   153	
   154				if (strcmp(pmask, psecret) == 0) {
   155					pmask += psecret_len + 1;
   156					goto mask_secret;
   157				}
   158	
   159				if (strncmp(pmask, psecret, psecret_len) == 0) {
   160					/*handle case: --password=xxxx */
   161					if ((psecret[0] == '-') && (psecret[1] == '-'))
   162						if (pmask[psecret_len] == '=') {
   163							pmask += psecret_len + 1;
   164							goto mask_secret;
   165						}
   166	
   167					if (psecret[0] == '-') {
   168						/*handle case: -password=xxxx or -p=xxxx*/
   169						if (pmask[psecret_len] == '=') {
   170							pmask += psecret_len + 1;
   171							goto mask_secret;
   172						}
   173	
   174						/*handle case: -pxxxx*/
   175						if (psecret_len == 2) {
   176							pmask += psecret_len;
   177							goto mask_secret;
   178						}
   179					}
   180				}
   181	
   182				if (psecret_len == 2) {
   183					pmask_len = strlen(pmask);
   184					/*handle case: -yp xxxx, such as: useradd -rp xxxx*/
   185					if ((pmask_len > 2) && (*pmask == '-')
   186					      && (pmask[pmask_len - 1] == psecret[1])) {
   187						pmask += pmask_len + 1;
   188						goto mask_secret;
   189					}
   190				}
   191	
   192				psecret += psecret_len + 1;
   193			}
   194	
   195			pmask += strlen(pmask);
   196			continue;
   197	
   198	mask_secret:
   199			for (; (pmask <= mask_arg_end) && (*pmask); pmask++)
   200				*pmask = 'Z';
   201		}
   202		rcu_read_unlock();
   203	
   204	copydata:
   205		size = arg_end - pos;
   206		size = min_t(size_t, size, count);
   207		if (copy_to_user(buf, mask_arg_start + pos - arg_start, size))
   208			goto cleanup_kbuf;
   209	
   210		total_copied = size;
   211	
   212	cleanup_kbuf:
   213		kfree(kbuf);
   214	
   215	exit_err:
   216		return total_copied;
   217	}
   218	

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