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