Re: [PATCH RFC DRAFT 15/50] nstree: add listns()

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

Hi Christian,

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

[auto build test WARNING on 3a8660878839faadb4f1a6dd72c3179c1df56787]

url:    https://github.com/intel-lab-lkp/linux/commits/Christian-Brauner/libfs-allow-to-specify-s_d_flags/20251021-200829
base:   3a8660878839faadb4f1a6dd72c3179c1df56787
patch link:    https://lore.kernel.org/r/20251021-work-namespace-nstree-listns-v1-15-ad44261a8a5b%40kernel.org
patch subject: [PATCH RFC DRAFT 15/50] nstree: add listns()
config: x86_64-buildonly-randconfig-004-20251022 (https://download.01.org/0day-ci/archive/20251022/202510221241.1ROUwVQu-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251022/202510221241.1ROUwVQu-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/202510221241.1ROUwVQu-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> kernel/nstree.c:499:11: warning: variable 'ns' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
     499 |         else if (kls->user_ns_id)
         |                  ^~~~~~~~~~~~~~~
   kernel/nstree.c:501:7: note: uninitialized use occurs here
     501 |         if (!ns)
         |              ^~
   kernel/nstree.c:499:7: note: remove the 'if' if its condition is always true
     499 |         else if (kls->user_ns_id)
         |              ^~~~~~~~~~~~~~~~~~~~
     500 |                 ns = lookup_ns_id(kls->user_ns_id, CLONE_NEWUSER);
   kernel/nstree.c:490:22: note: initialize the variable 'ns' to silence this warning
     490 |         struct ns_common *ns, *first_ns = NULL;
         |                             ^
         |                              = NULL
   1 warning generated.


vim +499 kernel/nstree.c

   485	
   486	static ssize_t do_listns_userns(struct klistns *kls)
   487	{
   488		u64 *ns_ids = kls->kns_ids;
   489		size_t nr_ns_ids = kls->nr_ns_ids;
   490		struct ns_common *ns, *first_ns = NULL;
   491		const struct list_head *head;
   492		bool userns_capable;
   493		ssize_t ret;
   494	
   495		VFS_WARN_ON_ONCE(!kls->user_ns_id);
   496	
   497		if (kls->user_ns_id == LISTNS_CURRENT_USER)
   498			ns = to_ns_common(current_user_ns());
 > 499		else if (kls->user_ns_id)
   500			ns = lookup_ns_id(kls->user_ns_id, CLONE_NEWUSER);
   501		if (!ns)
   502			return -EINVAL;
   503		kls->user_ns = to_user_ns(ns);
   504	
   505		/*
   506		 * Use the rbtree to find the first namespace we care about and
   507		 * then use it's list entry to iterate from there.
   508		 */
   509		if (kls->last_ns_id) {
   510			kls->first_ns = lookup_ns_owner_at(kls->last_ns_id + 1, ns);
   511			if (!kls->first_ns)
   512				return -ENOENT;
   513			first_ns = kls->first_ns;
   514		}
   515	
   516		ret = 0;
   517		head = &to_ns_common(kls->user_ns)->ns_owner;
   518		userns_capable = ns_capable_noaudit(kls->user_ns, CAP_SYS_ADMIN);
   519		guard(rcu)();
   520		if (!first_ns)
   521			first_ns = list_entry_rcu(head->next, typeof(*ns), ns_owner_entry);
   522		for (ns = first_ns; &ns->ns_owner_entry != head && nr_ns_ids;
   523		     ns = list_entry_rcu(ns->ns_owner_entry.next, typeof(*ns), ns_owner_entry)) {
   524			if (kls->ns_type && !(kls->ns_type & ns->ns_type))
   525				continue;
   526			if (!__ns_ref_active_read(ns))
   527				continue;
   528			if (!userns_capable && !is_current_namespace(ns) &&
   529			    ((ns->ns_type != CLONE_NEWUSER) ||
   530			     !ns_capable_noaudit(to_user_ns(ns), CAP_SYS_ADMIN)))
   531				continue;
   532			*ns_ids = ns->ns_id;
   533			ns_ids++;
   534			nr_ns_ids--;
   535			ret++;
   536		}
   537	
   538		return ret;
   539	}
   540	

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