tree: https://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux.git debugfs_namespaces head: aa77168aed303d914b4c11a2edaddbca3f1feda1 commit: 738289244f9f67ce3281dfece66c6e2f728b6501 [1/3] debugfs: add ns entry config: nds32-allyesconfig (attached as .config) compiler: nds32le-linux-gcc (GCC) 8.1.0 reproduce: wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross git checkout 738289244f9f67ce3281dfece66c6e2f728b6501 # save the attached .config to linux build tree GCC_VERSION=8.1.0 make.cross ARCH=nds32 If you fix the issue, kindly add following tag Reported-by: kbuild test robot <lkp(a)intel.com&gt; All error/warnings (new ones prefixed by >>): fs/nsfs.c:19:30: error: conflicting type qualifiers for 'ns_file_operations' const struct file_operations ns_file_operations = { ^~~~~~~~~~~~~~~~~~ In file included from fs/nsfs.c:12: include/linux/nsfs.h:6:31: note: previous declaration of 'ns_file_operations' was here extern struct file_operations ns_file_operations; ^~~~~~~~~~~~~~~~~~ fs/nsfs.c: In function 'ns_ioctl': fs/nsfs.c:196:7: error: 'NS_GET_USERNS' undeclared (first use in this function); did you mean 'F_GET_SEALS'? case NS_GET_USERNS: ^~~~~~~~~~~~~ F_GET_SEALS fs/nsfs.c:196:7: note: each undeclared identifier is reported only once for each function it appears in case NS_GET_PARENT: ^~~~~~~~~~~~~ CLONE_PARENT case NS_GET_NSTYPE: ^~~~~~~~~~~~~ fs/nsfs.c:204:7: error: 'NS_GET_OWNER_UID' undeclared (first use in this function); did you mean 'F_GETOWNER_UIDS'? case NS_GET_OWNER_UID: ^~~~~~~~~~~~~~~~ F_GETOWNER_UIDS fs/nsfs.c: In function 'proc_ns_fget': fs/nsfs.c:244:15: error: implicit declaration of function 'debugfs_real_fops' [-Werror=implicit-function-declaration] real_fops = debugfs_real_fops(file); ^~~~~~~~~~~~~~~~~ real_fops = debugfs_real_fops(file); ^ cc1: some warnings being treated as errors vim +198 fs/nsfs.c 6786741dbf99e4 Andrey Vagin 2016-09-06 186 6786741dbf99e4 Andrey Vagin 2016-09-06 187 static long ns_ioctl(struct file *filp, unsigned int ioctl, 6786741dbf99e4 Andrey Vagin 2016-09-06 188 unsigned long arg) 6786741dbf99e4 Andrey Vagin 2016-09-06 189 { d95fa3c76a66b6 Michael Kerrisk (man-pages 2017-01-25 190) struct user_namespace *user_ns; 6786741dbf99e4 Andrey Vagin 2016-09-06 191 struct ns_common *ns = get_proc_ns(file_inode(filp)); d95fa3c76a66b6 Michael Kerrisk (man-pages 2017-01-25 192) uid_t __user *argp; d95fa3c76a66b6 Michael Kerrisk (man-pages 2017-01-25 193) uid_t uid; 6786741dbf99e4 Andrey Vagin 2016-09-06 194 6786741dbf99e4 Andrey Vagin 2016-09-06 195 switch (ioctl) { 6786741dbf99e4 Andrey Vagin 2016-09-06 @196 case NS_GET_USERNS: 6786741dbf99e4 Andrey Vagin 2016-09-06 197 return open_related_ns(ns, ns_get_owner); a7306ed8d94af7 Andrey Vagin 2016-09-06 @198 case NS_GET_PARENT: a7306ed8d94af7 Andrey Vagin 2016-09-06 199 if (!ns->ops->get_parent) a7306ed8d94af7 Andrey Vagin 2016-09-06 200 return -EINVAL; a7306ed8d94af7 Andrey Vagin 2016-09-06 201 return open_related_ns(ns, ns->ops->get_parent); e5ff5ce6e20ee2 Michael Kerrisk (man-pages 2017-01-25 @202) case NS_GET_NSTYPE: e5ff5ce6e20ee2 Michael Kerrisk (man-pages 2017-01-25 203) return ns->ops->type; d95fa3c76a66b6 Michael Kerrisk (man-pages 2017-01-25 @204) case NS_GET_OWNER_UID: d95fa3c76a66b6 Michael Kerrisk (man-pages 2017-01-25 205) if (ns->ops->type != CLONE_NEWUSER) d95fa3c76a66b6 Michael Kerrisk (man-pages 2017-01-25 206) return -EINVAL; d95fa3c76a66b6 Michael Kerrisk (man-pages 2017-01-25 207) user_ns = container_of(ns, struct user_namespace, ns); d95fa3c76a66b6 Michael Kerrisk (man-pages 2017-01-25 208) argp = (uid_t __user *) arg; d95fa3c76a66b6 Michael Kerrisk (man-pages 2017-01-25 209) uid = from_kuid_munged(current_user_ns(), user_ns->owner); d95fa3c76a66b6 Michael Kerrisk (man-pages 2017-01-25 210) return put_user(uid, argp); 6786741dbf99e4 Andrey Vagin 2016-09-06 211 default: 6786741dbf99e4 Andrey Vagin 2016-09-06 212 return -ENOTTY; 6786741dbf99e4 Andrey Vagin 2016-09-06 213 } 6786741dbf99e4 Andrey Vagin 2016-09-06 214 } 6786741dbf99e4 Andrey Vagin 2016-09-06 215 e149ed2b805fef Al Viro 2014-11-01 216 int ns_get_name(char *buf, size_t size, struct task_struct *task, e149ed2b805fef Al Viro 2014-11-01 217 const struct proc_ns_operations *ns_ops) e149ed2b805fef Al Viro 2014-11-01 218 { e149ed2b805fef Al Viro 2014-11-01 219 struct ns_common *ns; e149ed2b805fef Al Viro 2014-11-01 220 int res = -ENOENT; 25b14e92af1a56 Kirill Tkhai 2017-05-08 221 const char *name; e149ed2b805fef Al Viro 2014-11-01 222 ns = ns_ops->get(task); e149ed2b805fef Al Viro 2014-11-01 223 if (ns) { 25b14e92af1a56 Kirill Tkhai 2017-05-08 224 name = ns_ops->real_ns_name ? : ns_ops->name; 25b14e92af1a56 Kirill Tkhai 2017-05-08 225 res = snprintf(buf, size, "%s:[%u]", name, ns->inum); e149ed2b805fef Al Viro 2014-11-01 226 ns_ops->put(ns); e149ed2b805fef Al Viro 2014-11-01 227 } e149ed2b805fef Al Viro 2014-11-01 228 return res; e149ed2b805fef Al Viro 2014-11-01 229 } e149ed2b805fef Al Viro 2014-11-01 230 e149ed2b805fef Al Viro 2014-11-01 231 struct file *proc_ns_fget(int fd) e149ed2b805fef Al Viro 2014-11-01 232 { e149ed2b805fef Al Viro 2014-11-01 233 struct file *file; 738289244f9f67 Christian Brauner 2019-10-11 234 const struct file_operations *real_fops; e149ed2b805fef Al Viro 2014-11-01 235 e149ed2b805fef Al Viro 2014-11-01 236 file = fget(fd); e149ed2b805fef Al Viro 2014-11-01 237 if (!file) e149ed2b805fef Al Viro 2014-11-01 238 return ERR_PTR(-EBADF); e149ed2b805fef Al Viro 2014-11-01 239 738289244f9f67 Christian Brauner 2019-10-11 240 if (file->f_op != &ns_file_operations) { 738289244f9f67 Christian Brauner 2019-10-11 241 if (file_dentry(file)->d_sb->s_magic != DEBUGFS_MAGIC) e149ed2b805fef Al Viro 2014-11-01 242 goto out_invalid; e149ed2b805fef Al Viro 2014-11-01 243 738289244f9f67 Christian Brauner 2019-10-11 @244 real_fops = debugfs_real_fops(file); 738289244f9f67 Christian Brauner 2019-10-11 245 if (real_fops != &ns_file_operations) 738289244f9f67 Christian Brauner 2019-10-11 246 goto out_invalid; 738289244f9f67 Christian Brauner 2019-10-11 247 } 738289244f9f67 Christian Brauner 2019-10-11 248 e149ed2b805fef Al Viro 2014-11-01 249 return file; e149ed2b805fef Al Viro 2014-11-01 250 e149ed2b805fef Al Viro 2014-11-01 251 out_invalid: e149ed2b805fef Al Viro 2014-11-01 252 fput(file); e149ed2b805fef Al Viro 2014-11-01 253 return ERR_PTR(-EINVAL); e149ed2b805fef Al Viro 2014-11-01 254 } e149ed2b805fef Al Viro 2014-11-01 255 :::::: The code at line 198 was first introduced by commit :::::: a7306ed8d94af729ecef8b6e37506a1c6fc14788 nsfs: add ioctl to get a parent namespace :::::: TO: Andrey Vagin <avagin(a)openvz.org&gt; :::::: CC: Eric W. Biederman <ebiederm(a)xmission.com&gt; --- 0-DAY kernel test infrastructure Open Source Technology Center https://lists.01.org/pipermail/kbuild-all Intel Corporation