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 put_user_ns(fc->user_ns); 161 fc->user_ns = get_user_ns(ctx->pid_ns->user_ns); 162 fc->s_fs_info = ctx->pid_ns; 163 return vfs_get_super(fc, vfs_get_keyed_super, proc_fill_super); 164 } 165 166 static void proc_fs_context_free(struct fs_context *fc) 167 { 168 struct proc_fs_context *ctx = fc->fs_private; 169 170 if (ctx->pid_ns) 171 put_pid_ns(ctx->pid_ns); 172 kfree(ctx); 173 } 174 175 static const struct fs_context_operations proc_fs_context_ops = { 176 .free = proc_fs_context_free, 177 .parse_param = proc_parse_param, 178 .get_tree = proc_get_tree, 179 .reconfigure = proc_reconfigure, 180 }; 181 182 static int proc_init_fs_context(struct fs_context *fc) 183 { 184 struct proc_fs_context *ctx; 185 186 ctx = kzalloc(sizeof(struct proc_fs_context), GFP_KERNEL); 187 if (!ctx) 188 return -ENOMEM; 189 190 ctx->pid_ns = get_pid_ns(task_active_pid_ns(current)); 191 fc->fs_private = ctx; 192 fc->ops = &proc_fs_context_ops; 193 return 0; 194 } 195 196 static void proc_kill_sb(struct super_block *sb) 197 { 198 struct pid_namespace *ns; 199 200 ns = (struct pid_namespace *)sb->s_fs_info; 201 if (ns->proc_self) 202 dput(ns->proc_self); 203 if (ns->proc_thread_self) 204 dput(ns->proc_thread_self); 205 kill_anon_super(sb); 206 put_pid_ns(ns); 207 } 208 209 static struct file_system_type proc_fs_type = { 210 .name = "proc", 211 .init_fs_context = proc_init_fs_context, 212 .parameters = &proc_fs_parameters, 213 .kill_sb = proc_kill_sb, 214 .fs_flags = FS_USERNS_MOUNT, 215 }; 216 217 void __init proc_root_init(void) 218 { 219 proc_init_kmemcache(); 220 set_proc_pid_nlink(); 221 proc_self_init(); 222 proc_thread_self_init(); 223 proc_symlink("mounts", NULL, "self/mounts"); 224 225 proc_net_init(); 226 proc_mkdir("fs", NULL); 227 proc_mkdir("driver", NULL); 228 proc_create_mount_point("fs/nfsd"); /* somewhere for the nfsd filesystem to be mounted */ 229 #if defined(CONFIG_SUN_OPENPROMFS) || defined(CONFIG_SUN_OPENPROMFS_MODULE) 230 /* just give it a mountpoint */ 231 proc_create_mount_point("openprom"); 232 #endif 233 proc_tty_init(); 234 proc_mkdir("bus", NULL); 235 proc_sys_init(); 236 237 register_filesystem(&proc_fs_type); 238 } 239 240 static int proc_root_getattr(const struct path *path, struct kstat *stat, 241 u32 request_mask, unsigned int query_flags) 242 { 243 generic_fillattr(d_inode(path->dentry), stat); 244 stat->nlink = proc_root.nlink + nr_processes(); 245 return 0; 246 } 247 248 static struct dentry *proc_root_lookup(struct inode * dir, struct dentry * dentry, unsigned int flags) 249 { 250 if (!proc_pid_lookup(dentry, flags)) 251 return NULL; 252 253 return proc_lookup(dir, dentry, flags); 254 } 255 256 static int proc_root_readdir(struct file *file, struct dir_context *ctx) 257 { 258 if (ctx->pos < FIRST_PROCESS_ENTRY) { 259 int error = proc_readdir(file, ctx); 260 if (unlikely(error <= 0)) 261 return error; 262 ctx->pos = FIRST_PROCESS_ENTRY; 263 } 264 265 return proc_pid_readdir(file, ctx); 266 } 267 268 /* 269 * The root /proc directory is special, as it has the 270 * <pid> directories. Thus we don't use the generic 271 * directory handling functions for that.. 272 */ 273 static const struct file_operations proc_root_operations = { 274 .read = generic_read_dir, 275 .iterate_shared = proc_root_readdir, 276 .llseek = generic_file_llseek, 277 }; 278 279 /* 280 * proc root can do almost nothing.. 281 */ 282 static const struct inode_operations proc_root_inode_operations = { 283 .lookup = proc_root_lookup, 284 .getattr = proc_root_getattr, 285 }; 286 287 /* 288 * This is the root "inode" in the /proc tree.. 289 */ 290 struct proc_dir_entry proc_root = { 291 .low_ino = PROC_ROOT_INO, 292 .namelen = 5, 293 .mode = S_IFDIR | S_IRUGO | S_IXUGO, 294 .nlink = 2, 295 .refcnt = REFCOUNT_INIT(1), 296 .proc_iops = &proc_root_inode_operations, 297 .proc_fops = &proc_root_operations, 298 .parent = &proc_root, 299 .subdir = RB_ROOT, 300 .name = "/proc", 301 }; 302 303 int pid_ns_prepare_proc(struct pid_namespace *ns) 304 { 305 struct proc_fs_context *ctx; 306 struct fs_context *fc; 307 struct vfsmount *mnt; 308 309 fc = fs_context_for_mount(&proc_fs_type, SB_KERNMOUNT); 310 if (IS_ERR(fc)) 311 return PTR_ERR(fc); 312 313 if (fc->user_ns != ns->user_ns) { 314 put_user_ns(fc->user_ns); 315 fc->user_ns = get_user_ns(ns->user_ns); 316 } 317 318 ctx = fc->fs_private; 319 if (ctx->pid_ns != ns) { 320 put_pid_ns(ctx->pid_ns); 321 get_pid_ns(ns); 322 ctx->pid_ns = ns; 323 } 324 325 mnt = fc_mount(fc); 326 put_fs_context(fc); 327 if (IS_ERR(mnt)) 328 return PTR_ERR(mnt); 329 330 ns->proc_mnt = mnt; 331 return 0; 332 } 333 334 void pid_ns_release_proc(struct pid_namespace *ns) 335 { 336 kern_unmount(ns->proc_mnt); 337 } 338