162 lines
3.4 KiB
C
162 lines
3.4 KiB
C
#include <linux/mount.h>
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#include <linux/file.h>
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#include <linux/fs.h>
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#include <linux/proc_ns.h>
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#include <linux/magic.h>
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#include <linux/ktime.h>
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static struct vfsmount *nsfs_mnt;
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static const struct file_operations ns_file_operations = {
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.llseek = no_llseek,
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};
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static char *ns_dname(struct dentry *dentry, char *buffer, int buflen)
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{
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struct inode *inode = dentry->d_inode;
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const struct proc_ns_operations *ns_ops = dentry->d_fsdata;
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return dynamic_dname(dentry, buffer, buflen, "%s:[%lu]",
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ns_ops->name, inode->i_ino);
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}
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static void ns_prune_dentry(struct dentry *dentry)
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{
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struct inode *inode = dentry->d_inode;
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if (inode) {
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struct ns_common *ns = inode->i_private;
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atomic_long_set(&ns->stashed, 0);
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}
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}
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const struct dentry_operations ns_dentry_operations =
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{
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.d_prune = ns_prune_dentry,
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.d_delete = always_delete_dentry,
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.d_dname = ns_dname,
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};
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static void nsfs_evict(struct inode *inode)
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{
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struct ns_common *ns = inode->i_private;
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clear_inode(inode);
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ns->ops->put(ns);
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}
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void *ns_get_path(struct path *path, struct task_struct *task,
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const struct proc_ns_operations *ns_ops)
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{
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struct vfsmount *mnt = mntget(nsfs_mnt);
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struct qstr qname = { .name = "", };
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struct dentry *dentry;
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struct inode *inode;
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struct ns_common *ns;
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unsigned long d;
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again:
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ns = ns_ops->get(task);
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if (!ns) {
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mntput(mnt);
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return ERR_PTR(-ENOENT);
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}
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rcu_read_lock();
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d = atomic_long_read(&ns->stashed);
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if (!d)
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goto slow;
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dentry = (struct dentry *)d;
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if (!lockref_get_not_dead(&dentry->d_lockref))
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goto slow;
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rcu_read_unlock();
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ns_ops->put(ns);
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got_it:
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path->mnt = mnt;
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path->dentry = dentry;
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return NULL;
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slow:
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rcu_read_unlock();
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inode = new_inode_pseudo(mnt->mnt_sb);
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if (!inode) {
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ns_ops->put(ns);
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mntput(mnt);
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return ERR_PTR(-ENOMEM);
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}
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inode->i_ino = ns->inum;
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inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
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inode->i_flags |= S_IMMUTABLE;
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inode->i_mode = S_IFREG | S_IRUGO;
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inode->i_fop = &ns_file_operations;
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inode->i_private = ns;
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dentry = d_alloc_pseudo(mnt->mnt_sb, &qname);
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if (!dentry) {
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iput(inode);
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mntput(mnt);
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return ERR_PTR(-ENOMEM);
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}
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d_instantiate(dentry, inode);
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dentry->d_fsdata = (void *)ns_ops;
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d = atomic_long_cmpxchg(&ns->stashed, 0, (unsigned long)dentry);
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if (d) {
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d_delete(dentry); /* make sure ->d_prune() does nothing */
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dput(dentry);
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cpu_relax();
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goto again;
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}
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goto got_it;
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}
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int ns_get_name(char *buf, size_t size, struct task_struct *task,
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const struct proc_ns_operations *ns_ops)
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{
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struct ns_common *ns;
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int res = -ENOENT;
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ns = ns_ops->get(task);
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if (ns) {
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res = snprintf(buf, size, "%s:[%u]", ns_ops->name, ns->inum);
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ns_ops->put(ns);
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}
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return res;
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}
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struct file *proc_ns_fget(int fd)
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{
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struct file *file;
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file = fget(fd);
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if (!file)
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return ERR_PTR(-EBADF);
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if (file->f_op != &ns_file_operations)
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goto out_invalid;
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return file;
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out_invalid:
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fput(file);
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return ERR_PTR(-EINVAL);
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}
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static const struct super_operations nsfs_ops = {
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.statfs = simple_statfs,
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.evict_inode = nsfs_evict,
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};
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static struct dentry *nsfs_mount(struct file_system_type *fs_type,
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int flags, const char *dev_name, void *data)
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{
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return mount_pseudo(fs_type, "nsfs:", &nsfs_ops,
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&ns_dentry_operations, NSFS_MAGIC);
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}
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static struct file_system_type nsfs = {
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.name = "nsfs",
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.mount = nsfs_mount,
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.kill_sb = kill_anon_super,
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};
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void __init nsfs_init(void)
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{
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nsfs_mnt = kern_mount(&nsfs);
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if (IS_ERR(nsfs_mnt))
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panic("can't set nsfs up\n");
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nsfs_mnt->mnt_sb->s_flags &= ~MS_NOUSER;
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}
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