Re: [PATCH v19 07/12] landlock: Support filesystem access-control

From: kernel test robot <lkp@intel.com>
To: kbuild-all@lists.01.org
Subject: Re: [PATCH v19 07/12] landlock: Support filesystem access-control
Date: Wed, 08 Jul 2020 04:40:55 +0800	[thread overview]
Message-ID: <202007080427.dVWPaIKW%lkp@intel.com> (raw)
In-Reply-To: <20200707180955.53024-8-mic@digikod.net>

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Hi "Mickaël,

I love your patch! Perhaps something to improve:

[auto build test WARNING on kselftest/next]
[also build test WARNING on pcmoore-selinux/next linus/master v5.8-rc4 next-20200707]
[cannot apply to security/next-testing]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use  as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Micka-l-Sala-n/Landlock-LSM/20200708-022251
base:   https://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest.git next
config: ia64-allmodconfig (attached as .config)
compiler: ia64-linux-gcc (GCC) 9.3.0
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
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=ia64 

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 >>):

   In file included from include/linux/bits.h:23,
                    from include/linux/bitops.h:5,
                    from include/linux/kernel.h:12,
                    from include/linux/list.h:9,
                    from include/linux/dcache.h:6,
                    from security/landlock/fs.c:11:
   security/landlock/fs.c: In function 'check_access_path':
   include/linux/bits.h:26:28: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits]
      26 |   __builtin_constant_p((l) > (h)), (l) > (h), 0)))
         |                            ^
   include/linux/build_bug.h:16:62: note: in definition of macro 'BUILD_BUG_ON_ZERO'
      16 | #define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); })))
         |                                                              ^
   include/linux/bits.h:45:3: note: in expansion of macro 'GENMASK_INPUT_CHECK'
      45 |  (GENMASK_INPUT_CHECK(h, l) + __GENMASK_ULL(h, l))
         |   ^~~~~~~~~~~~~~~~~~~
>> security/landlock/fs.c:216:15: note: in expansion of macro 'GENMASK_ULL'
     216 |  layer_mask = GENMASK_ULL(domain->nb_layers - 1, 0);
         |               ^~~~~~~~~~~
   include/linux/bits.h:26:40: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits]
      26 |   __builtin_constant_p((l) > (h)), (l) > (h), 0)))
         |                                        ^
   include/linux/build_bug.h:16:62: note: in definition of macro 'BUILD_BUG_ON_ZERO'
      16 | #define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); })))
         |                                                              ^
   include/linux/bits.h:45:3: note: in expansion of macro 'GENMASK_INPUT_CHECK'
      45 |  (GENMASK_INPUT_CHECK(h, l) + __GENMASK_ULL(h, l))
         |   ^~~~~~~~~~~~~~~~~~~
>> security/landlock/fs.c:216:15: note: in expansion of macro 'GENMASK_ULL'
     216 |  layer_mask = GENMASK_ULL(domain->nb_layers - 1, 0);
         |               ^~~~~~~~~~~

vim +/GENMASK_ULL +216 security/landlock/fs.c

   194	
   195	static int check_access_path(const struct landlock_ruleset *const domain,
   196			const struct path *const path, u32 access_request)
   197	{
   198		bool allow = false;
   199		struct path walker_path;
   200		u64 layer_mask;
   201	
   202		if (WARN_ON_ONCE(!domain || !path))
   203			return 0;
   204		/*
   205		 * Allows access to pseudo filesystems that will never be mountable
   206		 * (e.g. sockfs, pipefs), but can still be reachable through
   207		 * /proc/self/fd .
   208		 */
   209		if ((path->dentry->d_sb->s_flags & SB_NOUSER) ||
   210				(d_is_positive(path->dentry) &&
   211				 unlikely(IS_PRIVATE(d_backing_inode(path->dentry)))))
   212			return 0;
   213		if (WARN_ON_ONCE(domain->nb_layers < 1))
   214			return -EACCES;
   215	
 > 216		layer_mask = GENMASK_ULL(domain->nb_layers - 1, 0);
   217		/*
   218		 * An access request which is not handled by the domain should be
   219		 * allowed.
   220		 */
   221		access_request &= domain->fs_access_mask;
   222		if (access_request == 0)
   223			return 0;
   224		walker_path = *path;
   225		path_get(&walker_path);
   226		/*
   227		 * We need to walk through all the hierarchy to not miss any relevant
   228		 * restriction.
   229		 */
   230		while (check_access_path_continue(domain, &walker_path, access_request,
   231					&allow, &layer_mask)) {
   232			struct dentry *parent_dentry;
   233	
   234	jump_up:
   235			/*
   236			 * Does not work with orphaned/private mounts like overlayfs
   237			 * layers for now (cf. ovl_path_real() and ovl_path_open()).
   238			 */
   239			if (walker_path.dentry == walker_path.mnt->mnt_root) {
   240				if (follow_up(&walker_path)) {
   241					/* Ignores hidden mount points. */
   242					goto jump_up;
   243				} else {
   244					/*
   245					 * Stops at the real root.  Denies access
   246					 * because not all layers have granted access.
   247					 */
   248					allow = false;
   249					break;
   250				}
   251			}
   252			if (unlikely(IS_ROOT(walker_path.dentry))) {
   253				/*
   254				 * Stops at disconnected root directories.  Only allows
   255				 * access to internal filesystems (e.g. nsfs which is
   256				 * reachable through /proc/self/ns).
   257				 */
   258				allow = !!(walker_path.mnt->mnt_flags & MNT_INTERNAL);
   259				break;
   260			}
   261			parent_dentry = dget_parent(walker_path.dentry);
   262			dput(walker_path.dentry);
   263			walker_path.dentry = parent_dentry;
   264		}
   265		path_put(&walker_path);
   266		return allow ? 0 : -EACCES;
   267	}
   268	

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

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