[linux-next:master 1231/1936] fs/kernfs/mount.c:258:57: sparse: sparse: incorrect type in argument 1 (different address spaces)

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

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
head:   7702d0130dc002bab2c3571ddb6ff68f82d99aea
commit: 973256a7be6ed574f242995c15a8aa80cc0cc566 [1231/1936] VFS: rename lookup_one_len family to lookup_noperm and remove permission check
config: x86_64-randconfig-122-20250408 (https://download.01.org/0day-ci/archive/20250409/202504090310.xjNpww93-lkp@intel.com/config)
compiler: clang version 20.1.2 (https://github.com/llvm/llvm-project 58df0ef89dd64126512e4ee27b4ac3fd8ddf6247)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250409/202504090310.xjNpww93-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202504090310.xjNpww93-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
   fs/kernfs/mount.c:258:57: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected char const * @@     got char const [noderef] __rcu *name @@
   fs/kernfs/mount.c:258:57: sparse:     expected char const *
   fs/kernfs/mount.c:258:57: sparse:     got char const [noderef] __rcu *name
   fs/kernfs/mount.c:258:57: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected char const * @@     got char const [noderef] __rcu *name @@
   fs/kernfs/mount.c:258:57: sparse:     expected char const *
   fs/kernfs/mount.c:258:57: sparse:     got char const [noderef] __rcu *name
>> fs/kernfs/mount.c:258:57: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected char const *const p @@     got char const [noderef] __rcu *name @@
   fs/kernfs/mount.c:258:57: sparse:     expected char const *const p
   fs/kernfs/mount.c:258:57: sparse:     got char const [noderef] __rcu *name
   fs/kernfs/mount.c:258:57: sparse: sparse: incorrect type in initializer (different address spaces) @@     expected unsigned char const *name @@     got char const [noderef] __rcu *name @@
   fs/kernfs/mount.c:258:57: sparse:     expected unsigned char const *name
   fs/kernfs/mount.c:258:57: sparse:     got char const [noderef] __rcu *name

vim +258 fs/kernfs/mount.c

   199	
   200	/**
   201	 * kernfs_node_dentry - get a dentry for the given kernfs_node
   202	 * @kn: kernfs_node for which a dentry is needed
   203	 * @sb: the kernfs super_block
   204	 *
   205	 * Return: the dentry pointer
   206	 */
   207	struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
   208					  struct super_block *sb)
   209	{
   210		struct dentry *dentry;
   211		struct kernfs_node *knparent;
   212		struct kernfs_root *root;
   213	
   214		BUG_ON(sb->s_op != &kernfs_sops);
   215	
   216		dentry = dget(sb->s_root);
   217	
   218		/* Check if this is the root kernfs_node */
   219		if (!rcu_access_pointer(kn->__parent))
   220			return dentry;
   221	
   222		root = kernfs_root(kn);
   223		/*
   224		 * As long as kn is valid, its parent can not vanish. This is cgroup's
   225		 * kn so it can't have its parent replaced. Therefore it is safe to use
   226		 * the ancestor node outside of the RCU or locked section.
   227		 */
   228		if (WARN_ON_ONCE(!(root->flags & KERNFS_ROOT_INVARIANT_PARENT)))
   229			return ERR_PTR(-EINVAL);
   230		scoped_guard(rcu) {
   231			knparent = find_next_ancestor(kn, NULL);
   232		}
   233		if (WARN_ON(!knparent)) {
   234			dput(dentry);
   235			return ERR_PTR(-EINVAL);
   236		}
   237	
   238		do {
   239			struct dentry *dtmp;
   240			struct kernfs_node *kntmp;
   241			const char *name;
   242	
   243			if (kn == knparent)
   244				return dentry;
   245	
   246			scoped_guard(rwsem_read, &root->kernfs_rwsem) {
   247				kntmp = find_next_ancestor(kn, knparent);
   248				if (WARN_ON(!kntmp)) {
   249					dput(dentry);
   250					return ERR_PTR(-EINVAL);
   251				}
   252				name = kstrdup(kernfs_rcu_name(kntmp), GFP_KERNEL);
   253			}
   254			if (!name) {
   255				dput(dentry);
   256				return ERR_PTR(-ENOMEM);
   257			}
 > 258			dtmp = lookup_noperm_positive_unlocked(&QSTR(kntmp->name), dentry);
   259			dput(dentry);
   260			kfree(name);
   261			if (IS_ERR(dtmp))
   262				return dtmp;
   263			knparent = kntmp;
   264			dentry = dtmp;
   265		} while (true);
   266	}
   267	

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