1 /* 2 * fs/sysfs/symlink.c - operations for initializing and mounting sysfs 3 * 4 * Copyright (c) 2001-3 Patrick Mochel 5 * Copyright (c) 2007 SUSE Linux Products GmbH 6 * Copyright (c) 2007 Tejun Heo <teheo@suse.de> 7 * 8 * This file is released under the GPLv2. 9 * 10 * Please see Documentation/filesystems/sysfs.txt for more information. 11 */ 12 13 #define DEBUG 14 15 #include <linux/fs.h> 16 #include <linux/mount.h> 17 #include <linux/pagemap.h> 18 #include <linux/init.h> 19 #include <linux/module.h> 20 #include <linux/magic.h> 21 #include <linux/slab.h> 22 #include <linux/user_namespace.h> 23 24 #include "sysfs.h" 25 26 27 static struct vfsmount *sysfs_mnt; 28 struct kmem_cache *sysfs_dir_cachep; 29 30 static const struct super_operations sysfs_ops = { 31 .statfs = simple_statfs, 32 .drop_inode = generic_delete_inode, 33 .evict_inode = sysfs_evict_inode, 34 }; 35 36 struct sysfs_dirent sysfs_root = { 37 .s_name = "", 38 .s_count = ATOMIC_INIT(1), 39 .s_flags = SYSFS_DIR | (KOBJ_NS_TYPE_NONE << SYSFS_NS_TYPE_SHIFT), 40 .s_mode = S_IFDIR | S_IRUGO | S_IXUGO, 41 .s_ino = 1, 42 }; 43 44 static int sysfs_fill_super(struct super_block *sb, void *data, int silent) 45 { 46 struct inode *inode; 47 struct dentry *root; 48 49 sb->s_blocksize = PAGE_CACHE_SIZE; 50 sb->s_blocksize_bits = PAGE_CACHE_SHIFT; 51 sb->s_magic = SYSFS_MAGIC; 52 sb->s_op = &sysfs_ops; 53 sb->s_time_gran = 1; 54 55 /* get root inode, initialize and unlock it */ 56 mutex_lock(&sysfs_mutex); 57 inode = sysfs_get_inode(sb, &sysfs_root); 58 mutex_unlock(&sysfs_mutex); 59 if (!inode) { 60 pr_debug("sysfs: could not get root inode\n"); 61 return -ENOMEM; 62 } 63 64 /* instantiate and link root dentry */ 65 root = d_make_root(inode); 66 if (!root) { 67 pr_debug("%s: could not get root dentry!\n", __func__); 68 return -ENOMEM; 69 } 70 root->d_fsdata = &sysfs_root; 71 sb->s_root = root; 72 sb->s_d_op = &sysfs_dentry_ops; 73 return 0; 74 } 75 76 static int sysfs_test_super(struct super_block *sb, void *data) 77 { 78 struct sysfs_super_info *sb_info = sysfs_info(sb); 79 struct sysfs_super_info *info = data; 80 enum kobj_ns_type type; 81 int found = 1; 82 83 for (type = KOBJ_NS_TYPE_NONE; type < KOBJ_NS_TYPES; type++) { 84 if (sb_info->ns[type] != info->ns[type]) 85 found = 0; 86 } 87 return found; 88 } 89 90 static int sysfs_set_super(struct super_block *sb, void *data) 91 { 92 int error; 93 error = set_anon_super(sb, data); 94 if (!error) 95 sb->s_fs_info = data; 96 return error; 97 } 98 99 static void free_sysfs_super_info(struct sysfs_super_info *info) 100 { 101 int type; 102 for (type = KOBJ_NS_TYPE_NONE; type < KOBJ_NS_TYPES; type++) 103 kobj_ns_drop(type, info->ns[type]); 104 kfree(info); 105 } 106 107 static struct dentry *sysfs_mount(struct file_system_type *fs_type, 108 int flags, const char *dev_name, void *data) 109 { 110 struct sysfs_super_info *info; 111 enum kobj_ns_type type; 112 struct super_block *sb; 113 int error; 114 115 if (!(flags & MS_KERNMOUNT)) { 116 if (!capable(CAP_SYS_ADMIN) && !fs_fully_visible(fs_type)) 117 return ERR_PTR(-EPERM); 118 119 for (type = KOBJ_NS_TYPE_NONE; type < KOBJ_NS_TYPES; type++) { 120 if (!kobj_ns_current_may_mount(type)) 121 return ERR_PTR(-EPERM); 122 } 123 } 124 125 info = kzalloc(sizeof(*info), GFP_KERNEL); 126 if (!info) 127 return ERR_PTR(-ENOMEM); 128 129 for (type = KOBJ_NS_TYPE_NONE; type < KOBJ_NS_TYPES; type++) 130 info->ns[type] = kobj_ns_grab_current(type); 131 132 sb = sget(fs_type, sysfs_test_super, sysfs_set_super, flags, info); 133 if (IS_ERR(sb) || sb->s_fs_info != info) 134 free_sysfs_super_info(info); 135 if (IS_ERR(sb)) 136 return ERR_CAST(sb); 137 if (!sb->s_root) { 138 error = sysfs_fill_super(sb, data, flags & MS_SILENT ? 1 : 0); 139 if (error) { 140 deactivate_locked_super(sb); 141 return ERR_PTR(error); 142 } 143 sb->s_flags |= MS_ACTIVE; 144 } 145 146 return dget(sb->s_root); 147 } 148 149 static void sysfs_kill_sb(struct super_block *sb) 150 { 151 struct sysfs_super_info *info = sysfs_info(sb); 152 /* Remove the superblock from fs_supers/s_instances 153 * so we can't find it, before freeing sysfs_super_info. 154 */ 155 kill_anon_super(sb); 156 free_sysfs_super_info(info); 157 } 158 159 static struct file_system_type sysfs_fs_type = { 160 .name = "sysfs", 161 .mount = sysfs_mount, 162 .kill_sb = sysfs_kill_sb, 163 .fs_flags = FS_USERNS_MOUNT, 164 }; 165 166 int __init sysfs_init(void) 167 { 168 int err = -ENOMEM; 169 170 sysfs_dir_cachep = kmem_cache_create("sysfs_dir_cache", 171 sizeof(struct sysfs_dirent), 172 0, 0, NULL); 173 if (!sysfs_dir_cachep) 174 goto out; 175 176 err = sysfs_inode_init(); 177 if (err) 178 goto out_err; 179 180 err = register_filesystem(&sysfs_fs_type); 181 if (!err) { 182 sysfs_mnt = kern_mount(&sysfs_fs_type); 183 if (IS_ERR(sysfs_mnt)) { 184 printk(KERN_ERR "sysfs: could not mount!\n"); 185 err = PTR_ERR(sysfs_mnt); 186 sysfs_mnt = NULL; 187 unregister_filesystem(&sysfs_fs_type); 188 goto out_err; 189 } 190 } else 191 goto out_err; 192 out: 193 return err; 194 out_err: 195 kmem_cache_destroy(sysfs_dir_cachep); 196 sysfs_dir_cachep = NULL; 197 goto out; 198 } 199 200 #undef sysfs_get 201 struct sysfs_dirent *sysfs_get(struct sysfs_dirent *sd) 202 { 203 return __sysfs_get(sd); 204 } 205 EXPORT_SYMBOL_GPL(sysfs_get); 206 207 #undef sysfs_put 208 void sysfs_put(struct sysfs_dirent *sd) 209 { 210 __sysfs_put(sd); 211 } 212 EXPORT_SYMBOL_GPL(sysfs_put); 213