1 #include <linux/mount.h> 2 #include <linux/file.h> 3 #include <linux/fs.h> 4 #include <linux/proc_ns.h> 5 #include <linux/magic.h> 6 #include <linux/ktime.h> 7 #include <linux/seq_file.h> 8 9 static struct vfsmount *nsfs_mnt; 10 11 static const struct file_operations ns_file_operations = { 12 .llseek = no_llseek, 13 }; 14 15 static char *ns_dname(struct dentry *dentry, char *buffer, int buflen) 16 { 17 struct inode *inode = d_inode(dentry); 18 const struct proc_ns_operations *ns_ops = dentry->d_fsdata; 19 20 return dynamic_dname(dentry, buffer, buflen, "%s:[%lu]", 21 ns_ops->name, inode->i_ino); 22 } 23 24 static void ns_prune_dentry(struct dentry *dentry) 25 { 26 struct inode *inode = d_inode(dentry); 27 if (inode) { 28 struct ns_common *ns = inode->i_private; 29 atomic_long_set(&ns->stashed, 0); 30 } 31 } 32 33 const struct dentry_operations ns_dentry_operations = 34 { 35 .d_prune = ns_prune_dentry, 36 .d_delete = always_delete_dentry, 37 .d_dname = ns_dname, 38 }; 39 40 static void nsfs_evict(struct inode *inode) 41 { 42 struct ns_common *ns = inode->i_private; 43 clear_inode(inode); 44 ns->ops->put(ns); 45 } 46 47 void *ns_get_path(struct path *path, struct task_struct *task, 48 const struct proc_ns_operations *ns_ops) 49 { 50 struct vfsmount *mnt = mntget(nsfs_mnt); 51 struct qstr qname = { .name = "", }; 52 struct dentry *dentry; 53 struct inode *inode; 54 struct ns_common *ns; 55 unsigned long d; 56 57 again: 58 ns = ns_ops->get(task); 59 if (!ns) { 60 mntput(mnt); 61 return ERR_PTR(-ENOENT); 62 } 63 rcu_read_lock(); 64 d = atomic_long_read(&ns->stashed); 65 if (!d) 66 goto slow; 67 dentry = (struct dentry *)d; 68 if (!lockref_get_not_dead(&dentry->d_lockref)) 69 goto slow; 70 rcu_read_unlock(); 71 ns_ops->put(ns); 72 got_it: 73 path->mnt = mnt; 74 path->dentry = dentry; 75 return NULL; 76 slow: 77 rcu_read_unlock(); 78 inode = new_inode_pseudo(mnt->mnt_sb); 79 if (!inode) { 80 ns_ops->put(ns); 81 mntput(mnt); 82 return ERR_PTR(-ENOMEM); 83 } 84 inode->i_ino = ns->inum; 85 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; 86 inode->i_flags |= S_IMMUTABLE; 87 inode->i_mode = S_IFREG | S_IRUGO; 88 inode->i_fop = &ns_file_operations; 89 inode->i_private = ns; 90 91 dentry = d_alloc_pseudo(mnt->mnt_sb, &qname); 92 if (!dentry) { 93 iput(inode); 94 mntput(mnt); 95 return ERR_PTR(-ENOMEM); 96 } 97 d_instantiate(dentry, inode); 98 dentry->d_fsdata = (void *)ns_ops; 99 d = atomic_long_cmpxchg(&ns->stashed, 0, (unsigned long)dentry); 100 if (d) { 101 d_delete(dentry); /* make sure ->d_prune() does nothing */ 102 dput(dentry); 103 cpu_relax(); 104 goto again; 105 } 106 goto got_it; 107 } 108 109 int ns_get_name(char *buf, size_t size, struct task_struct *task, 110 const struct proc_ns_operations *ns_ops) 111 { 112 struct ns_common *ns; 113 int res = -ENOENT; 114 ns = ns_ops->get(task); 115 if (ns) { 116 res = snprintf(buf, size, "%s:[%u]", ns_ops->name, ns->inum); 117 ns_ops->put(ns); 118 } 119 return res; 120 } 121 122 struct file *proc_ns_fget(int fd) 123 { 124 struct file *file; 125 126 file = fget(fd); 127 if (!file) 128 return ERR_PTR(-EBADF); 129 130 if (file->f_op != &ns_file_operations) 131 goto out_invalid; 132 133 return file; 134 135 out_invalid: 136 fput(file); 137 return ERR_PTR(-EINVAL); 138 } 139 140 static int nsfs_show_path(struct seq_file *seq, struct dentry *dentry) 141 { 142 struct inode *inode = d_inode(dentry); 143 const struct proc_ns_operations *ns_ops = dentry->d_fsdata; 144 145 seq_printf(seq, "%s:[%lu]", ns_ops->name, inode->i_ino); 146 return 0; 147 } 148 149 static const struct super_operations nsfs_ops = { 150 .statfs = simple_statfs, 151 .evict_inode = nsfs_evict, 152 .show_path = nsfs_show_path, 153 }; 154 static struct dentry *nsfs_mount(struct file_system_type *fs_type, 155 int flags, const char *dev_name, void *data) 156 { 157 return mount_pseudo(fs_type, "nsfs:", &nsfs_ops, 158 &ns_dentry_operations, NSFS_MAGIC); 159 } 160 static struct file_system_type nsfs = { 161 .name = "nsfs", 162 .mount = nsfs_mount, 163 .kill_sb = kill_anon_super, 164 }; 165 166 void __init nsfs_init(void) 167 { 168 nsfs_mnt = kern_mount(&nsfs); 169 if (IS_ERR(nsfs_mnt)) 170 panic("can't set nsfs up\n"); 171 nsfs_mnt->mnt_sb->s_flags &= ~MS_NOUSER; 172 } 173