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_fs_parameters[] = { 45 fsparam_u32("gid", Opt_gid), 46 fsparam_u32("hidepid", Opt_hidepid), 47 {} 48 }; 49 50 static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param) 51 { 52 struct proc_fs_context *ctx = fc->fs_private; 53 struct fs_parse_result result; 54 int opt; 55 56 opt = fs_parse(fc, proc_fs_parameters, param, &result); 57 if (opt < 0) 58 return opt; 59 60 switch (opt) { 61 case Opt_gid: 62 ctx->gid = result.uint_32; 63 break; 64 65 case Opt_hidepid: 66 ctx->hidepid = result.uint_32; 67 if (ctx->hidepid < HIDEPID_OFF || 68 ctx->hidepid > HIDEPID_INVISIBLE) 69 return invalfc(fc, "hidepid value must be between 0 and 2.\n"); 70 break; 71 72 default: 73 return -EINVAL; 74 } 75 76 ctx->mask |= 1 << opt; 77 return 0; 78 } 79 80 static void proc_apply_options(struct super_block *s, 81 struct fs_context *fc, 82 struct pid_namespace *pid_ns, 83 struct user_namespace *user_ns) 84 { 85 struct proc_fs_context *ctx = fc->fs_private; 86 87 if (ctx->mask & (1 << Opt_gid)) 88 pid_ns->pid_gid = make_kgid(user_ns, ctx->gid); 89 if (ctx->mask & (1 << Opt_hidepid)) 90 pid_ns->hide_pid = ctx->hidepid; 91 } 92 93 static int proc_fill_super(struct super_block *s, struct fs_context *fc) 94 { 95 struct pid_namespace *pid_ns = get_pid_ns(s->s_fs_info); 96 struct inode *root_inode; 97 int ret; 98 99 proc_apply_options(s, fc, pid_ns, current_user_ns()); 100 101 /* User space would break if executables or devices appear on proc */ 102 s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV; 103 s->s_flags |= SB_NODIRATIME | SB_NOSUID | SB_NOEXEC; 104 s->s_blocksize = 1024; 105 s->s_blocksize_bits = 10; 106 s->s_magic = PROC_SUPER_MAGIC; 107 s->s_op = &proc_sops; 108 s->s_time_gran = 1; 109 110 /* 111 * procfs isn't actually a stacking filesystem; however, there is 112 * too much magic going on inside it to permit stacking things on 113 * top of it 114 */ 115 s->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH; 116 117 /* procfs dentries and inodes don't require IO to create */ 118 s->s_shrink.seeks = 0; 119 120 pde_get(&proc_root); 121 root_inode = proc_get_inode(s, &proc_root); 122 if (!root_inode) { 123 pr_err("proc_fill_super: get root inode failed\n"); 124 return -ENOMEM; 125 } 126 127 s->s_root = d_make_root(root_inode); 128 if (!s->s_root) { 129 pr_err("proc_fill_super: allocate dentry failed\n"); 130 return -ENOMEM; 131 } 132 133 ret = proc_setup_self(s); 134 if (ret) { 135 return ret; 136 } 137 return proc_setup_thread_self(s); 138 } 139 140 static int proc_reconfigure(struct fs_context *fc) 141 { 142 struct super_block *sb = fc->root->d_sb; 143 struct pid_namespace *pid = sb->s_fs_info; 144 145 sync_filesystem(sb); 146 147 proc_apply_options(sb, fc, pid, current_user_ns()); 148 return 0; 149 } 150 151 static int proc_get_tree(struct fs_context *fc) 152 { 153 struct proc_fs_context *ctx = fc->fs_private; 154 155 return get_tree_keyed(fc, proc_fill_super, ctx->pid_ns); 156 } 157 158 static void proc_fs_context_free(struct fs_context *fc) 159 { 160 struct proc_fs_context *ctx = fc->fs_private; 161 162 put_pid_ns(ctx->pid_ns); 163 kfree(ctx); 164 } 165 166 static const struct fs_context_operations proc_fs_context_ops = { 167 .free = proc_fs_context_free, 168 .parse_param = proc_parse_param, 169 .get_tree = proc_get_tree, 170 .reconfigure = proc_reconfigure, 171 }; 172 173 static int proc_init_fs_context(struct fs_context *fc) 174 { 175 struct proc_fs_context *ctx; 176 177 ctx = kzalloc(sizeof(struct proc_fs_context), GFP_KERNEL); 178 if (!ctx) 179 return -ENOMEM; 180 181 ctx->pid_ns = get_pid_ns(task_active_pid_ns(current)); 182 put_user_ns(fc->user_ns); 183 fc->user_ns = get_user_ns(ctx->pid_ns->user_ns); 184 fc->fs_private = ctx; 185 fc->ops = &proc_fs_context_ops; 186 return 0; 187 } 188 189 static void proc_kill_sb(struct super_block *sb) 190 { 191 struct pid_namespace *ns; 192 193 ns = (struct pid_namespace *)sb->s_fs_info; 194 if (ns->proc_self) 195 dput(ns->proc_self); 196 if (ns->proc_thread_self) 197 dput(ns->proc_thread_self); 198 kill_anon_super(sb); 199 200 /* Make the pid namespace safe for the next mount of proc */ 201 ns->proc_self = NULL; 202 ns->proc_thread_self = NULL; 203 ns->pid_gid = GLOBAL_ROOT_GID; 204 ns->hide_pid = 0; 205 206 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 | FS_DISALLOW_NOTIFY_PERM, 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_dir_ops = &proc_root_operations, 298 .parent = &proc_root, 299 .subdir = RB_ROOT, 300 .name = "/proc", 301 }; 302