1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * linux/fs/proc/root.c 4 * 5 * Copyright (C) 1991, 1992 Linus Torvalds 6 * 7 * proc root directory handling functions 8 */ 9 10 #include <linux/uaccess.h> 11 12 #include <linux/errno.h> 13 #include <linux/time.h> 14 #include <linux/proc_fs.h> 15 #include <linux/stat.h> 16 #include <linux/init.h> 17 #include <linux/sched.h> 18 #include <linux/sched/stat.h> 19 #include <linux/module.h> 20 #include <linux/bitops.h> 21 #include <linux/user_namespace.h> 22 #include <linux/fs_context.h> 23 #include <linux/mount.h> 24 #include <linux/pid_namespace.h> 25 #include <linux/fs_parser.h> 26 #include <linux/cred.h> 27 #include <linux/magic.h> 28 #include <linux/slab.h> 29 30 #include "internal.h" 31 32 struct proc_fs_context { 33 struct pid_namespace *pid_ns; 34 unsigned int mask; 35 int hidepid; 36 int gid; 37 }; 38 39 enum proc_param { 40 Opt_gid, 41 Opt_hidepid, 42 }; 43 44 static const struct fs_parameter_spec proc_param_specs[] = { 45 fsparam_u32("gid", Opt_gid), 46 fsparam_u32("hidepid", Opt_hidepid), 47 {} 48 }; 49 50 static const struct fs_parameter_description proc_fs_parameters = { 51 .name = "proc", 52 .specs = proc_param_specs, 53 }; 54 55 static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param) 56 { 57 struct proc_fs_context *ctx = fc->fs_private; 58 struct fs_parse_result result; 59 int opt; 60 61 opt = fs_parse(fc, &proc_fs_parameters, param, &result); 62 if (opt < 0) 63 return opt; 64 65 switch (opt) { 66 case Opt_gid: 67 ctx->gid = result.uint_32; 68 break; 69 70 case Opt_hidepid: 71 ctx->hidepid = result.uint_32; 72 if (ctx->hidepid < HIDEPID_OFF || 73 ctx->hidepid > HIDEPID_INVISIBLE) 74 return invalf(fc, "proc: hidepid value must be between 0 and 2.\n"); 75 break; 76 77 default: 78 return -EINVAL; 79 } 80 81 ctx->mask |= 1 << opt; 82 return 0; 83 } 84 85 static void proc_apply_options(struct super_block *s, 86 struct fs_context *fc, 87 struct pid_namespace *pid_ns, 88 struct user_namespace *user_ns) 89 { 90 struct proc_fs_context *ctx = fc->fs_private; 91 92 if (ctx->mask & (1 << Opt_gid)) 93 pid_ns->pid_gid = make_kgid(user_ns, ctx->gid); 94 if (ctx->mask & (1 << Opt_hidepid)) 95 pid_ns->hide_pid = ctx->hidepid; 96 } 97 98 static int proc_fill_super(struct super_block *s, struct fs_context *fc) 99 { 100 struct pid_namespace *pid_ns = get_pid_ns(s->s_fs_info); 101 struct inode *root_inode; 102 int ret; 103 104 proc_apply_options(s, fc, pid_ns, current_user_ns()); 105 106 /* User space would break if executables or devices appear on proc */ 107 s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV; 108 s->s_flags |= SB_NODIRATIME | SB_NOSUID | SB_NOEXEC; 109 s->s_blocksize = 1024; 110 s->s_blocksize_bits = 10; 111 s->s_magic = PROC_SUPER_MAGIC; 112 s->s_op = &proc_sops; 113 s->s_time_gran = 1; 114 115 /* 116 * procfs isn't actually a stacking filesystem; however, there is 117 * too much magic going on inside it to permit stacking things on 118 * top of it 119 */ 120 s->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH; 121 122 /* procfs dentries and inodes don't require IO to create */ 123 s->s_shrink.seeks = 0; 124 125 pde_get(&proc_root); 126 root_inode = proc_get_inode(s, &proc_root); 127 if (!root_inode) { 128 pr_err("proc_fill_super: get root inode failed\n"); 129 return -ENOMEM; 130 } 131 132 s->s_root = d_make_root(root_inode); 133 if (!s->s_root) { 134 pr_err("proc_fill_super: allocate dentry failed\n"); 135 return -ENOMEM; 136 } 137 138 ret = proc_setup_self(s); 139 if (ret) { 140 return ret; 141 } 142 return proc_setup_thread_self(s); 143 } 144 145 static int proc_reconfigure(struct fs_context *fc) 146 { 147 struct super_block *sb = fc->root->d_sb; 148 struct pid_namespace *pid = sb->s_fs_info; 149 150 sync_filesystem(sb); 151 152 proc_apply_options(sb, fc, pid, current_user_ns()); 153 return 0; 154 } 155 156 static int proc_get_tree(struct fs_context *fc) 157 { 158 struct proc_fs_context *ctx = fc->fs_private; 159 160 fc->s_fs_info = ctx->pid_ns; 161 return vfs_get_super(fc, vfs_get_keyed_super, proc_fill_super); 162 } 163 164 static void proc_fs_context_free(struct fs_context *fc) 165 { 166 struct proc_fs_context *ctx = fc->fs_private; 167 168 put_pid_ns(ctx->pid_ns); 169 kfree(ctx); 170 } 171 172 static const struct fs_context_operations proc_fs_context_ops = { 173 .free = proc_fs_context_free, 174 .parse_param = proc_parse_param, 175 .get_tree = proc_get_tree, 176 .reconfigure = proc_reconfigure, 177 }; 178 179 static int proc_init_fs_context(struct fs_context *fc) 180 { 181 struct proc_fs_context *ctx; 182 183 ctx = kzalloc(sizeof(struct proc_fs_context), GFP_KERNEL); 184 if (!ctx) 185 return -ENOMEM; 186 187 ctx->pid_ns = get_pid_ns(task_active_pid_ns(current)); 188 put_user_ns(fc->user_ns); 189 fc->user_ns = get_user_ns(ctx->pid_ns->user_ns); 190 fc->fs_private = ctx; 191 fc->ops = &proc_fs_context_ops; 192 return 0; 193 } 194 195 static void proc_kill_sb(struct super_block *sb) 196 { 197 struct pid_namespace *ns; 198 199 ns = (struct pid_namespace *)sb->s_fs_info; 200 if (ns->proc_self) 201 dput(ns->proc_self); 202 if (ns->proc_thread_self) 203 dput(ns->proc_thread_self); 204 kill_anon_super(sb); 205 put_pid_ns(ns); 206 } 207 208 static struct file_system_type proc_fs_type = { 209 .name = "proc", 210 .init_fs_context = proc_init_fs_context, 211 .parameters = &proc_fs_parameters, 212 .kill_sb = proc_kill_sb, 213 .fs_flags = FS_USERNS_MOUNT | FS_DISALLOW_NOTIFY_PERM, 214 }; 215 216 void __init proc_root_init(void) 217 { 218 proc_init_kmemcache(); 219 set_proc_pid_nlink(); 220 proc_self_init(); 221 proc_thread_self_init(); 222 proc_symlink("mounts", NULL, "self/mounts"); 223 224 proc_net_init(); 225 proc_mkdir("fs", NULL); 226 proc_mkdir("driver", NULL); 227 proc_create_mount_point("fs/nfsd"); /* somewhere for the nfsd filesystem to be mounted */ 228 #if defined(CONFIG_SUN_OPENPROMFS) || defined(CONFIG_SUN_OPENPROMFS_MODULE) 229 /* just give it a mountpoint */ 230 proc_create_mount_point("openprom"); 231 #endif 232 proc_tty_init(); 233 proc_mkdir("bus", NULL); 234 proc_sys_init(); 235 236 register_filesystem(&proc_fs_type); 237 } 238 239 static int proc_root_getattr(const struct path *path, struct kstat *stat, 240 u32 request_mask, unsigned int query_flags) 241 { 242 generic_fillattr(d_inode(path->dentry), stat); 243 stat->nlink = proc_root.nlink + nr_processes(); 244 return 0; 245 } 246 247 static struct dentry *proc_root_lookup(struct inode * dir, struct dentry * dentry, unsigned int flags) 248 { 249 if (!proc_pid_lookup(dentry, flags)) 250 return NULL; 251 252 return proc_lookup(dir, dentry, flags); 253 } 254 255 static int proc_root_readdir(struct file *file, struct dir_context *ctx) 256 { 257 if (ctx->pos < FIRST_PROCESS_ENTRY) { 258 int error = proc_readdir(file, ctx); 259 if (unlikely(error <= 0)) 260 return error; 261 ctx->pos = FIRST_PROCESS_ENTRY; 262 } 263 264 return proc_pid_readdir(file, ctx); 265 } 266 267 /* 268 * The root /proc directory is special, as it has the 269 * <pid> directories. Thus we don't use the generic 270 * directory handling functions for that.. 271 */ 272 static const struct file_operations proc_root_operations = { 273 .read = generic_read_dir, 274 .iterate_shared = proc_root_readdir, 275 .llseek = generic_file_llseek, 276 }; 277 278 /* 279 * proc root can do almost nothing.. 280 */ 281 static const struct inode_operations proc_root_inode_operations = { 282 .lookup = proc_root_lookup, 283 .getattr = proc_root_getattr, 284 }; 285 286 /* 287 * This is the root "inode" in the /proc tree.. 288 */ 289 struct proc_dir_entry proc_root = { 290 .low_ino = PROC_ROOT_INO, 291 .namelen = 5, 292 .mode = S_IFDIR | S_IRUGO | S_IXUGO, 293 .nlink = 2, 294 .refcnt = REFCOUNT_INIT(1), 295 .proc_iops = &proc_root_inode_operations, 296 .proc_fops = &proc_root_operations, 297 .parent = &proc_root, 298 .subdir = RB_ROOT, 299 .name = "/proc", 300 }; 301 302 int pid_ns_prepare_proc(struct pid_namespace *ns) 303 { 304 struct proc_fs_context *ctx; 305 struct fs_context *fc; 306 struct vfsmount *mnt; 307 308 fc = fs_context_for_mount(&proc_fs_type, SB_KERNMOUNT); 309 if (IS_ERR(fc)) 310 return PTR_ERR(fc); 311 312 if (fc->user_ns != ns->user_ns) { 313 put_user_ns(fc->user_ns); 314 fc->user_ns = get_user_ns(ns->user_ns); 315 } 316 317 ctx = fc->fs_private; 318 if (ctx->pid_ns != ns) { 319 put_pid_ns(ctx->pid_ns); 320 get_pid_ns(ns); 321 ctx->pid_ns = ns; 322 } 323 324 mnt = fc_mount(fc); 325 put_fs_context(fc); 326 if (IS_ERR(mnt)) 327 return PTR_ERR(mnt); 328 329 ns->proc_mnt = mnt; 330 return 0; 331 } 332 333 void pid_ns_release_proc(struct pid_namespace *ns) 334 { 335 kern_unmount(ns->proc_mnt); 336 } 337