/* * linux/fs/namespace.c * * (C) Copyright Al Viro 2000, 2001 * Released under GPL v2. * * Based on code from fs/super.c, copyright Linus Torvalds and others. * Heavily rewritten. */ #include <linux/config.h> #include <linux/syscalls.h> #include <linux/slab.h> #include <linux/sched.h> #include <linux/smp_lock.h> #include <linux/init.h> #include <linux/quotaops.h> #include <linux/acct.h> #include <linux/capability.h> #include <linux/module.h> #include <linux/seq_file.h> #include <linux/namespace.h> #include <linux/namei.h> #include <linux/security.h> #include <linux/mount.h> #include <asm/uaccess.h> #include <asm/unistd.h> #include "pnode.h" extern int __init init_rootfs(void); #ifdef CONFIG_SYSFS extern int __init sysfs_init(void); #else static inline int sysfs_init(void) { return 0; } #endif /* spinlock for vfsmount related operations, inplace of dcache_lock */ __cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock); static int event; static struct list_head *mount_hashtable; static int hash_mask __read_mostly, hash_bits __read_mostly; static kmem_cache_t *mnt_cache; static struct rw_semaphore namespace_sem; /* /sys/fs */ decl_subsys(fs, NULL, NULL); EXPORT_SYMBOL_GPL(fs_subsys); static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry) { unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES); tmp += ((unsigned long)dentry / L1_CACHE_BYTES); tmp = tmp + (tmp >> hash_bits); return tmp & hash_mask; } struct vfsmount *alloc_vfsmnt(const char *name) { struct vfsmount *mnt = kmem_cache_alloc(mnt_cache, GFP_KERNEL); if (mnt) { memset(mnt, 0, sizeof(struct vfsmount)); atomic_set(&mnt->mnt_count, 1); INIT_LIST_HEAD(&mnt->mnt_hash); INIT_LIST_HEAD(&mnt->mnt_child); INIT_LIST_HEAD(&mnt->mnt_mounts); INIT_LIST_HEAD(&mnt->mnt_list); INIT_LIST_HEAD(&mnt->mnt_expire); INIT_LIST_HEAD(&mnt->mnt_share); INIT_LIST_HEAD(&mnt->mnt_slave_list); INIT_LIST_HEAD(&mnt->mnt_slave); if (name) { int size = strlen(name) + 1; char *newname = kmalloc(size, GFP_KERNEL); if (newname) { memcpy(newname, name, size); mnt->mnt_devname = newname; } } } return mnt; } void free_vfsmnt(struct vfsmount *mnt) { kfree(mnt->mnt_devname); kmem_cache_free(mnt_cache, mnt); } /* * find the first or last mount at @dentry on vfsmount @mnt depending on * @dir. If @dir is set return the first mount else return the last mount. */ struct vfsmount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry, int dir) { struct list_head *head = mount_hashtable + hash(mnt, dentry); struct list_head *tmp = head; struct vfsmount *p, *found = NULL; for (;;) { tmp = dir ? tmp->next : tmp->prev; p = NULL; if (tmp == head) break; p = list_entry(tmp, struct vfsmount, mnt_hash); if (p->mnt_parent == mnt && p->mnt_mountpoint == dentry) { found = p; break; } } return found; } /* * lookup_mnt increments the ref count before returning * the vfsmount struct. */ struct vfsmount *lookup_mnt(struct vfsmount *mnt, struct dentry *dentry) { struct vfsmount *child_mnt; spin_lock(&vfsmount_lock); if ((child_mnt = __lookup_mnt(mnt, dentry, 1))) mntget(child_mnt); spin_unlock(&vfsmount_lock); return child_mnt; } static inline int check_mnt(struct vfsmount *mnt) { return mnt->mnt_namespace == current->namespace; } static void touch_namespace(struct namespace *ns) { if (ns) { ns->event = ++event; wake_up_interruptible(&ns->poll); } } static void __touch_namespace(struct namespace *ns) { if (ns && ns->event != event) { ns->event = event; wake_up_interruptible(&ns->poll); } } static void detach_mnt(struct vfsmount *mnt, struct nameidata *old_nd) { old_nd->dentry = mnt->mnt_mountpoint; old_nd->mnt = mnt->mnt_parent; mnt->mnt_parent = mnt; mnt->mnt_mountpoint = mnt->mnt_root; list_del_init(&mnt->mnt_child); list_del_init(&mnt->mnt_hash); old_nd->dentry->d_mounted--; } void mnt_set_mountpoint(struct vfsmount *mnt, struct dentry *dentry, struct vfsmount *child_mnt) { child_mnt->mnt_parent = mntget(mnt); child_mnt->mnt_mountpoint = dget(dentry); dentry->d_mounted++; } static void attach_mnt(struct vfsmount *mnt, struct nameidata *nd) { mnt_set_mountpoint(nd->mnt, nd->dentry, mnt); list_add_tail(&mnt->mnt_hash, mount_hashtable + hash(nd->mnt, nd->dentry)); list_add_tail(&mnt->mnt_child, &nd->mnt->mnt_mounts); } /* * the caller must hold vfsmount_lock */ static void commit_tree(struct vfsmount *mnt) { struct vfsmount *parent = mnt->mnt_parent; struct vfsmount *m; LIST_HEAD(head); struct namespace *n = parent->mnt_namespace; BUG_ON(parent == mnt); list_add_tail(&head, &mnt->mnt_list); list_for_each_entry(m, &head, mnt_list) m->mnt_namespace = n; list_splice(&head, n->list.prev); list_add_tail(&mnt->mnt_hash, mount_hashtable + hash(parent, mnt->mnt_mountpoint)); list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); touch_namespace(n); } static struct vfsmount *next_mnt(struct vfsmount *p, struct vfsmount *root) { struct list_head *next = p->mnt_mounts.next; if (next == &p->mnt_mounts) { while (1) { if (p == root) return NULL; next = p->mnt_child.next; if (next != &p->mnt_parent->mnt_mounts) break; p = p->mnt_parent; } } return list_entry(next, struct vfsmount, mnt_child); } static struct vfsmount *skip_mnt_tree(struct vfsmount *p) { struct list_head *prev = p->mnt_mounts.prev; while (prev != &p->mnt_mounts) { p = list_entry(prev, struct vfsmount, mnt_child); prev = p->mnt_mounts.prev; } return p; } static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root, int flag) { struct super_block *sb = old->mnt_sb; struct vfsmount *mnt = alloc_vfsmnt(old->mnt_devname); if (mnt) { mnt->mnt_flags = old->mnt_flags; atomic_inc(&sb->s_active); mnt->mnt_sb = sb; mnt->mnt_root = dget(root); mnt->mnt_mountpoint = mnt->mnt_root; mnt->mnt_parent = mnt; if (flag & CL_SLAVE) { list_add(&mnt->mnt_slave, &old->mnt_slave_list); mnt->mnt_master = old; CLEAR_MNT_SHARED(mnt); } else { if ((flag & CL_PROPAGATION) || IS_MNT_SHARED(old)) list_add(&mnt->mnt_share, &old->mnt_share); if (IS_MNT_SLAVE(old)) list_add(&mnt->mnt_slave, &old->mnt_slave); mnt->mnt_master = old->mnt_master; } if (flag & CL_MAKE_SHARED) set_mnt_shared(mnt); /* stick the duplicate mount on the same expiry list * as the original if that was on one */ if (flag & CL_EXPIRE) { spin_lock(&vfsmount_lock); if (!list_empty(&old->mnt_expire)) list_add(&mnt->mnt_expire, &old->mnt_expire); spin_unlock(&vfsmount_lock); } } return mnt; } static inline void __mntput(struct vfsmount *mnt) { struct super_block *sb = mnt->mnt_sb; dput(mnt->mnt_root); free_vfsmnt(mnt); deactivate_super(sb); } void mntput_no_expire(struct vfsmount *mnt) { repeat: if (atomic_dec_and_lock(&mnt->mnt_count, &vfsmount_lock)) { if (likely(!mnt->mnt_pinned)) { spin_unlock(&vfsmount_lock); __mntput(mnt); return; } atomic_add(mnt->mnt_pinned + 1, &mnt->mnt_count); mnt->mnt_pinned = 0; spin_unlock(&vfsmount_lock); acct_auto_close_mnt(mnt); security_sb_umount_close(mnt); goto repeat; } } EXPORT_SYMBOL(mntput_no_expire); void mnt_pin(struct vfsmount *mnt) { spin_lock(&vfsmount_lock); mnt->mnt_pinned++; spin_unlock(&vfsmount_lock); } EXPORT_SYMBOL(mnt_pin); void mnt_unpin(struct vfsmount *mnt) { spin_lock(&vfsmount_lock); if (mnt->mnt_pinned) { atomic_inc(&mnt->mnt_count); mnt->mnt_pinned--; } spin_unlock(&vfsmount_lock); } EXPORT_SYMBOL(mnt_unpin); /* iterator */ static void *m_start(struct seq_file *m, loff_t *pos) { struct namespace *n = m->private; struct list_head *p; loff_t l = *pos; down_read(&namespace_sem); list_for_each(p, &n->list) if (!l--) return list_entry(p, struct vfsmount, mnt_list); return NULL; } static void *m_next(struct seq_file *m, void *v, loff_t *pos) { struct namespace *n = m->private; struct list_head *p = ((struct vfsmount *)v)->mnt_list.next; (*pos)++; return p == &n->list ? NULL : list_entry(p, struct vfsmount, mnt_list); } static void m_stop(struct seq_file *m, void *v) { up_read(&namespace_sem); } static inline void mangle(struct seq_file *m, const char *s) { seq_escape(m, s, " \t\n\\"); } static int show_vfsmnt(struct seq_file *m, void *v) { struct vfsmount *mnt = v; int err = 0; static struct proc_fs_info { int flag; char *str; } fs_info[] = { { MS_SYNCHRONOUS, ",sync" }, { MS_DIRSYNC, ",dirsync" }, { MS_MANDLOCK, ",mand" }, { 0, NULL } }; static struct proc_fs_info mnt_info[] = { { MNT_NOSUID, ",nosuid" }, { MNT_NODEV, ",nodev" }, { MNT_NOEXEC, ",noexec" }, { MNT_NOATIME, ",noatime" }, { MNT_NODIRATIME, ",nodiratime" }, { 0, NULL } }; struct proc_fs_info *fs_infop; mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none"); seq_putc(m, ' '); seq_path(m, mnt, mnt->mnt_root, " \t\n\\"); seq_putc(m, ' '); mangle(m, mnt->mnt_sb->s_type->name); seq_puts(m, mnt->mnt_sb->s_flags & MS_RDONLY ? " ro" : " rw"); for (fs_infop = fs_info; fs_infop->flag; fs_infop++) { if (mnt->mnt_sb->s_flags & fs_infop->flag) seq_puts(m, fs_infop->str); } for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) { if (mnt->mnt_flags & fs_infop->flag) seq_puts(m, fs_infop->str); } if (mnt->mnt_sb->s_op->show_options) err = mnt->mnt_sb->s_op->show_options(m, mnt); seq_puts(m, " 0 0\n"); return err; } struct seq_operations mounts_op = { .start = m_start, .next = m_next, .stop = m_stop, .show = show_vfsmnt }; /** * may_umount_tree - check if a mount tree is busy * @mnt: root of mount tree * * This is called to check if a tree of mounts has any * open files, pwds, chroots or sub mounts that are * busy. */ int may_umount_tree(struct vfsmount *mnt) { int actual_refs = 0; int minimum_refs = 0; struct vfsmount *p; spin_lock(&vfsmount_lock); for (p = mnt; p; p = next_mnt(p, mnt)) { actual_refs += atomic_read(&p->mnt_count); minimum_refs += 2; } spin_unlock(&vfsmount_lock); if (actual_refs > minimum_refs) return -EBUSY; return 0; } EXPORT_SYMBOL(may_umount_tree); /** * may_umount - check if a mount point is busy * @mnt: root of mount * * This is called to check if a mount point has any * open files, pwds, chroots or sub mounts. If the * mount has sub mounts this will return busy * regardless of whether the sub mounts are busy. * * Doesn't take quota and stuff into account. IOW, in some cases it will * give false negatives. The main reason why it's here is that we need * a non-destructive way to look for easily umountable filesystems. */ int may_umount(struct vfsmount *mnt) { int ret = 0; spin_lock(&vfsmount_lock); if (propagate_mount_busy(mnt, 2)) ret = -EBUSY; spin_unlock(&vfsmount_lock); return ret; } EXPORT_SYMBOL(may_umount); void release_mounts(struct list_head *head) { struct vfsmount *mnt; while (!list_empty(head)) { mnt = list_entry(head->next, struct vfsmount, mnt_hash); list_del_init(&mnt->mnt_hash); if (mnt->mnt_parent != mnt) { struct dentry *dentry; struct vfsmount *m; spin_lock(&vfsmount_lock); dentry = mnt->mnt_mountpoint; m = mnt->mnt_parent; mnt->mnt_mountpoint = mnt->mnt_root; mnt->mnt_parent = mnt; spin_unlock(&vfsmount_lock); dput(dentry); mntput(m); } mntput(mnt); } } void umount_tree(struct vfsmount *mnt, int propagate, struct list_head *kill) { struct vfsmount *p; for (p = mnt; p; p = next_mnt(p, mnt)) { list_del(&p->mnt_hash); list_add(&p->mnt_hash, kill); } if (propagate) propagate_umount(kill); list_for_each_entry(p, kill, mnt_hash) { list_del_init(&p->mnt_expire); list_del_init(&p->mnt_list); __touch_namespace(p->mnt_namespace); p->mnt_namespace = NULL; list_del_init(&p->mnt_child); if (p->mnt_parent != p) p->mnt_mountpoint->d_mounted--; change_mnt_propagation(p, MS_PRIVATE); } } static int do_umount(struct vfsmount *mnt, int flags) { struct super_block *sb = mnt->mnt_sb; int retval; LIST_HEAD(umount_list); retval = security_sb_umount(mnt, flags); if (retval) return retval; /* * Allow userspace to request a mountpoint be expired rather than * unmounting unconditionally. Unmount only happens if: * (1) the mark is already set (the mark is cleared by mntput()) * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount] */ if (flags & MNT_EXPIRE) { if (mnt == current->fs->rootmnt || flags & (MNT_FORCE | MNT_DETACH)) return -EINVAL; if (atomic_read(&mnt->mnt_count) != 2) return -EBUSY; if (!xchg(&mnt->mnt_expiry_mark, 1)) return -EAGAIN; } /* * If we may have to abort operations to get out of this * mount, and they will themselves hold resources we must * allow the fs to do things. In the Unix tradition of * 'Gee thats tricky lets do it in userspace' the umount_begin * might fail to complete on the first run through as other tasks * must return, and the like. Thats for the mount program to worry * about for the moment. */ lock_kernel(); if ((flags & MNT_FORCE) && sb->s_op->umount_begin) sb->s_op->umount_begin(sb); unlock_kernel(); /* * No sense to grab the lock for this test, but test itself looks * somewhat bogus. Suggestions for better replacement? * Ho-hum... In principle, we might treat that as umount + switch * to rootfs. GC would eventually take care of the old vfsmount. * Actually it makes sense, especially if rootfs would contain a * /reboot - static binary that would close all descriptors and * call reboot(9). Then init(8) could umount root and exec /reboot. */ if (mnt == current->fs->rootmnt && !(flags & MNT_DETACH)) { /* * Special case for "unmounting" root ... * we just try to remount it readonly. */ down_write(&sb->s_umount); if (!(sb->s_flags & MS_RDONLY)) { lock_kernel(); DQUOT_OFF(sb); retval = do_remount_sb(sb, MS_RDONLY, NULL, 0); unlock_kernel(); } up_write(&sb->s_umount); return retval; } down_write(&namespace_sem); spin_lock(&vfsmount_lock); event++; retval = -EBUSY; if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) { if (!list_empty(&mnt->mnt_list)) umount_tree(mnt, 1, &umount_list); retval = 0; } spin_unlock(&vfsmount_lock); if (retval) security_sb_umount_busy(mnt); up_write(&namespace_sem); release_mounts(&umount_list); return retval; } /* * Now umount can handle mount points as well as block devices. * This is important for filesystems which use unnamed block devices. * * We now support a flag for forced unmount like the other 'big iron' * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD */ asmlinkage long sys_umount(char __user * name, int flags) { struct nameidata nd; int retval; retval = __user_walk(name, LOOKUP_FOLLOW, &nd); if (retval) goto out; retval = -EINVAL; if (nd.dentry != nd.mnt->mnt_root) goto dput_and_out; if (!check_mnt(nd.mnt)) goto dput_and_out; retval = -EPERM; if (!capable(CAP_SYS_ADMIN)) goto dput_and_out; retval = do_umount(nd.mnt, flags); dput_and_out: path_release_on_umount(&nd); out: return retval; } #ifdef __ARCH_WANT_SYS_OLDUMOUNT /* * The 2.0 compatible umount. No flags. */ asmlinkage long sys_oldumount(char __user * name) { return sys_umount(name, 0); } #endif static int mount_is_safe(struct nameidata *nd) { if (capable(CAP_SYS_ADMIN)) return 0; return -EPERM; #ifdef notyet if (S_ISLNK(nd->dentry->d_inode->i_mode)) return -EPERM; if (nd->dentry->d_inode->i_mode & S_ISVTX) { if (current->uid != nd->dentry->d_inode->i_uid) return -EPERM; } if (vfs_permission(nd, MAY_WRITE)) return -EPERM; return 0; #endif } static int lives_below_in_same_fs(struct dentry *d, struct dentry *dentry) { while (1) { if (d == dentry) return 1; if (d == NULL || d == d->d_parent) return 0; d = d->d_parent; } } struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry, int flag) { struct vfsmount *res, *p, *q, *r, *s; struct nameidata nd; if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt)) return NULL; res = q = clone_mnt(mnt, dentry, flag); if (!q) goto Enomem; q->mnt_mountpoint = mnt->mnt_mountpoint; p = mnt; list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) { if (!lives_below_in_same_fs(r->mnt_mountpoint, dentry)) continue; for (s = r; s; s = next_mnt(s, r)) { if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(s)) { s = skip_mnt_tree(s); continue; } while (p != s->mnt_parent) { p = p->mnt_parent; q = q->mnt_parent; } p = s; nd.mnt = q; nd.dentry = p->mnt_mountpoint; q = clone_mnt(p, p->mnt_root, flag); if (!q) goto Enomem; spin_lock(&vfsmount_lock); list_add_tail(&q->mnt_list, &res->mnt_list); attach_mnt(q, &nd); spin_unlock(&vfsmount_lock); } } return res; Enomem: if (res) { LIST_HEAD(umount_list); spin_lock(&vfsmount_lock); umount_tree(res, 0, &umount_list); spin_unlock(&vfsmount_lock); release_mounts(&umount_list); } return NULL; } /* * @source_mnt : mount tree to be attached * @nd : place the mount tree @source_mnt is attached * @parent_nd : if non-null, detach the source_mnt from its parent and * store the parent mount and mountpoint dentry. * (done when source_mnt is moved) * * NOTE: in the table below explains the semantics when a source mount * of a given type is attached to a destination mount of a given type. * --------------------------------------------------------------------------- * | BIND MOUNT OPERATION | * |************************************************************************** * | source-->| shared | private | slave | unbindable | * | dest | | | | | * | | | | | | | * | v | | | | | * |************************************************************************** * | shared | shared (++) | shared (+) | shared(+++)| invalid | * | | | | | | * |non-shared| shared (+) | private | slave (*) | invalid | * *************************************************************************** * A bind operation clones the source mount and mounts the clone on the * destination mount. * * (++) the cloned mount is propagated to all the mounts in the propagation * tree of the destination mount and the cloned mount is added to * the peer group of the source mount. * (+) the cloned mount is created under the destination mount and is marked * as shared. The cloned mount is added to the peer group of the source * mount. * (+++) the mount is propagated to all the mounts in the propagation tree * of the destination mount and the cloned mount is made slave * of the same master as that of the source mount. The cloned mount * is marked as 'shared and slave'. * (*) the cloned mount is made a slave of the same master as that of the * source mount. * * --------------------------------------------------------------------------- * | MOVE MOUNT OPERATION | * |************************************************************************** * | source-->| shared | private | slave | unbindable | * | dest | | | | | * | | | | | | | * | v | | | | | * |************************************************************************** * | shared | shared (+) | shared (+) | shared(+++) | invalid | * | | | | | | * |non-shared| shared (+*) | private | slave (*) | unbindable | * *************************************************************************** * * (+) the mount is moved to the destination. And is then propagated to * all the mounts in the propagation tree of the destination mount. * (+*) the mount is moved to the destination. * (+++) the mount is moved to the destination and is then propagated to * all the mounts belonging to the destination mount's propagation tree. * the mount is marked as 'shared and slave'. * (*) the mount continues to be a slave at the new location. * * if the source mount is a tree, the operations explained above is * applied to each mount in the tree. * Must be called without spinlocks held, since this function can sleep * in allocations. */ static int attach_recursive_mnt(struct vfsmount *source_mnt, struct nameidata *nd, struct nameidata *parent_nd) { LIST_HEAD(tree_list); struct vfsmount *dest_mnt = nd->mnt; struct dentry *dest_dentry = nd->dentry; struct vfsmount *child, *p; if (propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list)) return -EINVAL; if (IS_MNT_SHARED(dest_mnt)) { for (p = source_mnt; p; p = next_mnt(p, source_mnt)) set_mnt_shared(p); } spin_lock(&vfsmount_lock); if (parent_nd) { detach_mnt(source_mnt, parent_nd); attach_mnt(source_mnt, nd); touch_namespace(current->namespace); } else { mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt); commit_tree(source_mnt); } list_for_each_entry_safe(child, p, &tree_list, mnt_hash) { list_del_init(&child->mnt_hash); commit_tree(child); } spin_unlock(&vfsmount_lock); return 0; } static int graft_tree(struct vfsmount *mnt, struct nameidata *nd) { int err; if (mnt->mnt_sb->s_flags & MS_NOUSER) return -EINVAL; if (S_ISDIR(nd->dentry->d_inode->i_mode) != S_ISDIR(mnt->mnt_root->d_inode->i_mode)) return -ENOTDIR; err = -ENOENT; mutex_lock(&nd->dentry->d_inode->i_mutex); if (IS_DEADDIR(nd->dentry->d_inode)) goto out_unlock; err = security_sb_check_sb(mnt, nd); if (err) goto out_unlock; err = -ENOENT; if (IS_ROOT(nd->dentry) || !d_unhashed(nd->dentry)) err = attach_recursive_mnt(mnt, nd, NULL); out_unlock: mutex_unlock(&nd->dentry->d_inode->i_mutex); if (!err) security_sb_post_addmount(mnt, nd); return err; } /* * recursively change the type of the mountpoint. */ static int do_change_type(struct nameidata *nd, int flag) { struct vfsmount *m, *mnt = nd->mnt; int recurse = flag & MS_REC; int type = flag & ~MS_REC; if (nd->dentry != nd->mnt->mnt_root) return -EINVAL; down_write(&namespace_sem); spin_lock(&vfsmount_lock); for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL)) change_mnt_propagation(m, type); spin_unlock(&vfsmount_lock); up_write(&namespace_sem); return 0; } /* * do loopback mount. */ static int do_loopback(struct nameidata *nd, char *old_name, int recurse) { struct nameidata old_nd; struct vfsmount *mnt = NULL; int err = mount_is_safe(nd); if (err) return err; if (!old_name || !*old_name) return -EINVAL; err = path_lookup(old_name, LOOKUP_FOLLOW, &old_nd); if (err) return err; down_write(&namespace_sem); err = -EINVAL; if (IS_MNT_UNBINDABLE(old_nd.mnt)) goto out; if (!check_mnt(nd->mnt) || !check_mnt(old_nd.mnt)) goto out; err = -ENOMEM; if (recurse) mnt = copy_tree(old_nd.mnt, old_nd.dentry, 0); else mnt = clone_mnt(old_nd.mnt, old_nd.dentry, 0); if (!mnt) goto out; err = graft_tree(mnt, nd); if (err) { LIST_HEAD(umount_list); spin_lock(&vfsmount_lock); umount_tree(mnt, 0, &umount_list); spin_unlock(&vfsmount_lock); release_mounts(&umount_list); } out: up_write(&namespace_sem); path_release(&old_nd); return err; } /* * change filesystem flags. dir should be a physical root of filesystem. * If you've mounted a non-root directory somewhere and want to do remount * on it - tough luck. */ static int do_remount(struct nameidata *nd, int flags, int mnt_flags, void *data) { int err; struct super_block *sb = nd->mnt->mnt_sb; if (!capable(CAP_SYS_ADMIN)) return -EPERM; if (!check_mnt(nd->mnt)) return -EINVAL; if (nd->dentry != nd->mnt->mnt_root) return -EINVAL; down_write(&sb->s_umount); err = do_remount_sb(sb, flags, data, 0); if (!err) nd->mnt->mnt_flags = mnt_flags; up_write(&sb->s_umount); if (!err) security_sb_post_remount(nd->mnt, flags, data); return err; } static inline int tree_contains_unbindable(struct vfsmount *mnt) { struct vfsmount *p; for (p = mnt; p; p = next_mnt(p, mnt)) { if (IS_MNT_UNBINDABLE(p)) return 1; } return 0; } static int do_move_mount(struct nameidata *nd, char *old_name) { struct nameidata old_nd, parent_nd; struct vfsmount *p; int err = 0; if (!capable(CAP_SYS_ADMIN)) return -EPERM; if (!old_name || !*old_name) return -EINVAL; err = path_lookup(old_name, LOOKUP_FOLLOW, &old_nd); if (err) return err; down_write(&namespace_sem); while (d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry)) ; err = -EINVAL; if (!check_mnt(nd->mnt) || !check_mnt(old_nd.mnt)) goto out; err = -ENOENT; mutex_lock(&nd->dentry->d_inode->i_mutex); if (IS_DEADDIR(nd->dentry->d_inode)) goto out1; if (!IS_ROOT(nd->dentry) && d_unhashed(nd->dentry)) goto out1; err = -EINVAL; if (old_nd.dentry != old_nd.mnt->mnt_root) goto out1; if (old_nd.mnt == old_nd.mnt->mnt_parent) goto out1; if (S_ISDIR(nd->dentry->d_inode->i_mode) != S_ISDIR(old_nd.dentry->d_inode->i_mode)) goto out1; /* * Don't move a mount residing in a shared parent. */ if (old_nd.mnt->mnt_parent && IS_MNT_SHARED(old_nd.mnt->mnt_parent)) goto out1; /* * Don't move a mount tree containing unbindable mounts to a destination * mount which is shared. */ if (IS_MNT_SHARED(nd->mnt) && tree_contains_unbindable(old_nd.mnt)) goto out1; err = -ELOOP; for (p = nd->mnt; p->mnt_parent != p; p = p->mnt_parent) if (p == old_nd.mnt) goto out1; if ((err = attach_recursive_mnt(old_nd.mnt, nd, &parent_nd))) goto out1; spin_lock(&vfsmount_lock); /* if the mount is moved, it should no longer be expire * automatically */ list_del_init(&old_nd.mnt->mnt_expire); spin_unlock(&vfsmount_lock); out1: mutex_unlock(&nd->dentry->d_inode->i_mutex); out: up_write(&namespace_sem); if (!err) path_release(&parent_nd); path_release(&old_nd); return err; } /* * create a new mount for userspace and request it to be added into the * namespace's tree */ static int do_new_mount(struct nameidata *nd, char *type, int flags, int mnt_flags, char *name, void *data) { struct vfsmount *mnt; if (!type || !memchr(type, 0, PAGE_SIZE)) return -EINVAL; /* we need capabilities... */ if (!capable(CAP_SYS_ADMIN)) return -EPERM; mnt = do_kern_mount(type, flags, name, data); if (IS_ERR(mnt)) return PTR_ERR(mnt); return do_add_mount(mnt, nd, mnt_flags, NULL); } /* * add a mount into a namespace's mount tree * - provide the option of adding the new mount to an expiration list */ int do_add_mount(struct vfsmount *newmnt, struct nameidata *nd, int mnt_flags, struct list_head *fslist) { int err; down_write(&namespace_sem); /* Something was mounted here while we slept */ while (d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry)) ; err = -EINVAL; if (!check_mnt(nd->mnt)) goto unlock; /* Refuse the same filesystem on the same mount point */ err = -EBUSY; if (nd->mnt->mnt_sb == newmnt->mnt_sb && nd->mnt->mnt_root == nd->dentry) goto unlock; err = -EINVAL; if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode)) goto unlock; newmnt->mnt_flags = mnt_flags; if ((err = graft_tree(newmnt, nd))) goto unlock; if (fslist) { /* add to the specified expiration list */ spin_lock(&vfsmount_lock); list_add_tail(&newmnt->mnt_expire, fslist); spin_unlock(&vfsmount_lock); } up_write(&namespace_sem); return 0; unlock: up_write(&namespace_sem); mntput(newmnt); return err; } EXPORT_SYMBOL_GPL(do_add_mount); static void expire_mount(struct vfsmount *mnt, struct list_head *mounts, struct list_head *umounts) { spin_lock(&vfsmount_lock); /* * Check if mount is still attached, if not, let whoever holds it deal * with the sucker */ if (mnt->mnt_parent == mnt) { spin_unlock(&vfsmount_lock); return; } /* * Check that it is still dead: the count should now be 2 - as * contributed by the vfsmount parent and the mntget above */ if (!propagate_mount_busy(mnt, 2)) { /* delete from the namespace */ touch_namespace(mnt->mnt_namespace); list_del_init(&mnt->mnt_list); mnt->mnt_namespace = NULL; umount_tree(mnt, 1, umounts); spin_unlock(&vfsmount_lock); } else { /* * Someone brought it back to life whilst we didn't have any * locks held so return it to the expiration list */ list_add_tail(&mnt->mnt_expire, mounts); spin_unlock(&vfsmount_lock); } } /* * process a list of expirable mountpoints with the intent of discarding any * mountpoints that aren't in use and haven't been touched since last we came * here */ void mark_mounts_for_expiry(struct list_head *mounts) { struct namespace *namespace; struct vfsmount *mnt, *next; LIST_HEAD(graveyard); if (list_empty(mounts)) return; spin_lock(&vfsmount_lock); /* extract from the expiration list every vfsmount that matches the * following criteria: * - only referenced by its parent vfsmount * - still marked for expiry (marked on the last call here; marks are * cleared by mntput()) */ list_for_each_entry_safe(mnt, next, mounts, mnt_expire) { if (!xchg(&mnt->mnt_expiry_mark, 1) || atomic_read(&mnt->mnt_count) != 1) continue; mntget(mnt); list_move(&mnt->mnt_expire, &graveyard); } /* * go through the vfsmounts we've just consigned to the graveyard to * - check that they're still dead * - delete the vfsmount from the appropriate namespace under lock * - dispose of the corpse */ while (!list_empty(&graveyard)) { LIST_HEAD(umounts); mnt = list_entry(graveyard.next, struct vfsmount, mnt_expire); list_del_init(&mnt->mnt_expire); /* don't do anything if the namespace is dead - all the * vfsmounts from it are going away anyway */ namespace = mnt->mnt_namespace; if (!namespace || !namespace->root) continue; get_namespace(namespace); spin_unlock(&vfsmount_lock); down_write(&namespace_sem); expire_mount(mnt, mounts, &umounts); up_write(&namespace_sem); release_mounts(&umounts); mntput(mnt); put_namespace(namespace); spin_lock(&vfsmount_lock); } spin_unlock(&vfsmount_lock); } EXPORT_SYMBOL_GPL(mark_mounts_for_expiry); /* * Some copy_from_user() implementations do not return the exact number of * bytes remaining to copy on a fault. But copy_mount_options() requires that. * Note that this function differs from copy_from_user() in that it will oops * on bad values of `to', rather than returning a short copy. */ static long exact_copy_from_user(void *to, const void __user * from, unsigned long n) { char *t = to; const char __user *f = from; char c; if (!access_ok(VERIFY_READ, from, n)) return n; while (n) { if (__get_user(c, f)) { memset(t, 0, n); break; } *t++ = c; f++; n--; } return n; } int copy_mount_options(const void __user * data, unsigned long *where) { int i; unsigned long page; unsigned long size; *where = 0; if (!data) return 0; if (!(page = __get_free_page(GFP_KERNEL))) return -ENOMEM; /* We only care that *some* data at the address the user * gave us is valid. Just in case, we'll zero * the remainder of the page. */ /* copy_from_user cannot cross TASK_SIZE ! */ size = TASK_SIZE - (unsigned long)data; if (size > PAGE_SIZE) size = PAGE_SIZE; i = size - exact_copy_from_user((void *)page, data, size); if (!i) { free_page(page); return -EFAULT; } if (i != PAGE_SIZE) memset((char *)page + i, 0, PAGE_SIZE - i); *where = page; return 0; } /* * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to * be given to the mount() call (ie: read-only, no-dev, no-suid etc). * * data is a (void *) that can point to any structure up to * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent * information (or be NULL). * * Pre-0.97 versions of mount() didn't have a flags word. * When the flags word was introduced its top half was required * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9. * Therefore, if this magic number is present, it carries no information * and must be discarded. */ long do_mount(char *dev_name, char *dir_name, char *type_page, unsigned long flags, void *data_page) { struct nameidata nd; int retval = 0; int mnt_flags = 0; /* Discard magic */ if ((flags & MS_MGC_MSK) == MS_MGC_VAL) flags &= ~MS_MGC_MSK; /* Basic sanity checks */ if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE)) return -EINVAL; if (dev_name && !memchr(dev_name, 0, PAGE_SIZE)) return -EINVAL; if (data_page) ((char *)data_page)[PAGE_SIZE - 1] = 0; /* Separate the per-mountpoint flags */ if (flags & MS_NOSUID) mnt_flags |= MNT_NOSUID; if (flags & MS_NODEV) mnt_flags |= MNT_NODEV; if (flags & MS_NOEXEC) mnt_flags |= MNT_NOEXEC; if (flags & MS_NOATIME) mnt_flags |= MNT_NOATIME; if (flags & MS_NODIRATIME) mnt_flags |= MNT_NODIRATIME; flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_NOATIME | MS_NODIRATIME); /* ... and get the mountpoint */ retval = path_lookup(dir_name, LOOKUP_FOLLOW, &nd); if (retval) return retval; retval = security_sb_mount(dev_name, &nd, type_page, flags, data_page); if (retval) goto dput_out; if (flags & MS_REMOUNT) retval = do_remount(&nd, flags & ~MS_REMOUNT, mnt_flags, data_page); else if (flags & MS_BIND) retval = do_loopback(&nd, dev_name, flags & MS_REC); else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) retval = do_change_type(&nd, flags); else if (flags & MS_MOVE) retval = do_move_mount(&nd, dev_name); else retval = do_new_mount(&nd, type_page, flags, mnt_flags, dev_name, data_page); dput_out: path_release(&nd); return retval; } /* * Allocate a new namespace structure and populate it with contents * copied from the namespace of the passed in task structure. */ struct namespace *dup_namespace(struct task_struct *tsk, struct fs_struct *fs) { struct namespace *namespace = tsk->namespace; struct namespace *new_ns; struct vfsmount *rootmnt = NULL, *pwdmnt = NULL, *altrootmnt = NULL; struct vfsmount *p, *q; new_ns = kmalloc(sizeof(struct namespace), GFP_KERNEL); if (!new_ns) return NULL; atomic_set(&new_ns->count, 1); INIT_LIST_HEAD(&new_ns->list); init_waitqueue_head(&new_ns->poll); new_ns->event = 0; down_write(&namespace_sem); /* First pass: copy the tree topology */ new_ns->root = copy_tree(namespace->root, namespace->root->mnt_root, CL_COPY_ALL | CL_EXPIRE); if (!new_ns->root) { up_write(&namespace_sem); kfree(new_ns); return NULL; } spin_lock(&vfsmount_lock); list_add_tail(&new_ns->list, &new_ns->root->mnt_list); spin_unlock(&vfsmount_lock); /* * Second pass: switch the tsk->fs->* elements and mark new vfsmounts * as belonging to new namespace. We have already acquired a private * fs_struct, so tsk->fs->lock is not needed. */ p = namespace->root; q = new_ns->root; while (p) { q->mnt_namespace = new_ns; if (fs) { if (p == fs->rootmnt) { rootmnt = p; fs->rootmnt = mntget(q); } if (p == fs->pwdmnt) { pwdmnt = p; fs->pwdmnt = mntget(q); } if (p == fs->altrootmnt) { altrootmnt = p; fs->altrootmnt = mntget(q); } } p = next_mnt(p, namespace->root); q = next_mnt(q, new_ns->root); } up_write(&namespace_sem); if (rootmnt) mntput(rootmnt); if (pwdmnt) mntput(pwdmnt); if (altrootmnt) mntput(altrootmnt); return new_ns; } int copy_namespace(int flags, struct task_struct *tsk) { struct namespace *namespace = tsk->namespace; struct namespace *new_ns; int err = 0; if (!namespace) return 0; get_namespace(namespace); if (!(flags & CLONE_NEWNS)) return 0; if (!capable(CAP_SYS_ADMIN)) { err = -EPERM; goto out; } new_ns = dup_namespace(tsk, tsk->fs); if (!new_ns) { err = -ENOMEM; goto out; } tsk->namespace = new_ns; out: put_namespace(namespace); return err; } asmlinkage long sys_mount(char __user * dev_name, char __user * dir_name, char __user * type, unsigned long flags, void __user * data) { int retval; unsigned long data_page; unsigned long type_page; unsigned long dev_page; char *dir_page; retval = copy_mount_options(type, &type_page); if (retval < 0) return retval; dir_page = getname(dir_name); retval = PTR_ERR(dir_page); if (IS_ERR(dir_page)) goto out1; retval = copy_mount_options(dev_name, &dev_page); if (retval < 0) goto out2; retval = copy_mount_options(data, &data_page); if (retval < 0) goto out3; lock_kernel(); retval = do_mount((char *)dev_page, dir_page, (char *)type_page, flags, (void *)data_page); unlock_kernel(); free_page(data_page); out3: free_page(dev_page); out2: putname(dir_page); out1: free_page(type_page); return retval; } /* * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values. * It can block. Requires the big lock held. */ void set_fs_root(struct fs_struct *fs, struct vfsmount *mnt, struct dentry *dentry) { struct dentry *old_root; struct vfsmount *old_rootmnt; write_lock(&fs->lock); old_root = fs->root; old_rootmnt = fs->rootmnt; fs->rootmnt = mntget(mnt); fs->root = dget(dentry); write_unlock(&fs->lock); if (old_root) { dput(old_root); mntput(old_rootmnt); } } /* * Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values. * It can block. Requires the big lock held. */ void set_fs_pwd(struct fs_struct *fs, struct vfsmount *mnt, struct dentry *dentry) { struct dentry *old_pwd; struct vfsmount *old_pwdmnt; write_lock(&fs->lock); old_pwd = fs->pwd; old_pwdmnt = fs->pwdmnt; fs->pwdmnt = mntget(mnt); fs->pwd = dget(dentry); write_unlock(&fs->lock); if (old_pwd) { dput(old_pwd); mntput(old_pwdmnt); } } static void chroot_fs_refs(struct nameidata *old_nd, struct nameidata *new_nd) { struct task_struct *g, *p; struct fs_struct *fs; read_lock(&tasklist_lock); do_each_thread(g, p) { task_lock(p); fs = p->fs; if (fs) { atomic_inc(&fs->count); task_unlock(p); if (fs->root == old_nd->dentry && fs->rootmnt == old_nd->mnt) set_fs_root(fs, new_nd->mnt, new_nd->dentry); if (fs->pwd == old_nd->dentry && fs->pwdmnt == old_nd->mnt) set_fs_pwd(fs, new_nd->mnt, new_nd->dentry); put_fs_struct(fs); } else task_unlock(p); } while_each_thread(g, p); read_unlock(&tasklist_lock); } /* * pivot_root Semantics: * Moves the root file system of the current process to the directory put_old, * makes new_root as the new root file system of the current process, and sets * root/cwd of all processes which had them on the current root to new_root. * * Restrictions: * The new_root and put_old must be directories, and must not be on the * same file system as the current process root. The put_old must be * underneath new_root, i.e. adding a non-zero number of /.. to the string * pointed to by put_old must yield the same directory as new_root. No other * file system may be mounted on put_old. After all, new_root is a mountpoint. * * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem. * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives * in this situation. * * Notes: * - we don't move root/cwd if they are not at the root (reason: if something * cared enough to change them, it's probably wrong to force them elsewhere) * - it's okay to pick a root that isn't the root of a file system, e.g. * /nfs/my_root where /nfs is the mount point. It must be a mountpoint, * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root * first. */ asmlinkage long sys_pivot_root(const char __user * new_root, const char __user * put_old) { struct vfsmount *tmp; struct nameidata new_nd, old_nd, parent_nd, root_parent, user_nd; int error; if (!capable(CAP_SYS_ADMIN)) return -EPERM; lock_kernel(); error = __user_walk(new_root, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &new_nd); if (error) goto out0; error = -EINVAL; if (!check_mnt(new_nd.mnt)) goto out1; error = __user_walk(put_old, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &old_nd); if (error) goto out1; error = security_sb_pivotroot(&old_nd, &new_nd); if (error) { path_release(&old_nd); goto out1; } read_lock(¤t->fs->lock); user_nd.mnt = mntget(current->fs->rootmnt); user_nd.dentry = dget(current->fs->root); read_unlock(¤t->fs->lock); down_write(&namespace_sem); mutex_lock(&old_nd.dentry->d_inode->i_mutex); error = -EINVAL; if (IS_MNT_SHARED(old_nd.mnt) || IS_MNT_SHARED(new_nd.mnt->mnt_parent) || IS_MNT_SHARED(user_nd.mnt->mnt_parent)) goto out2; if (!check_mnt(user_nd.mnt)) goto out2; error = -ENOENT; if (IS_DEADDIR(new_nd.dentry->d_inode)) goto out2; if (d_unhashed(new_nd.dentry) && !IS_ROOT(new_nd.dentry)) goto out2; if (d_unhashed(old_nd.dentry) && !IS_ROOT(old_nd.dentry)) goto out2; error = -EBUSY; if (new_nd.mnt == user_nd.mnt || old_nd.mnt == user_nd.mnt) goto out2; /* loop, on the same file system */ error = -EINVAL; if (user_nd.mnt->mnt_root != user_nd.dentry) goto out2; /* not a mountpoint */ if (user_nd.mnt->mnt_parent == user_nd.mnt) goto out2; /* not attached */ if (new_nd.mnt->mnt_root != new_nd.dentry) goto out2; /* not a mountpoint */ if (new_nd.mnt->mnt_parent == new_nd.mnt) goto out2; /* not attached */ tmp = old_nd.mnt; /* make sure we can reach put_old from new_root */ spin_lock(&vfsmount_lock); if (tmp != new_nd.mnt) { for (;;) { if (tmp->mnt_parent == tmp) goto out3; /* already mounted on put_old */ if (tmp->mnt_parent == new_nd.mnt) break; tmp = tmp->mnt_parent; } if (!is_subdir(tmp->mnt_mountpoint, new_nd.dentry)) goto out3; } else if (!is_subdir(old_nd.dentry, new_nd.dentry)) goto out3; detach_mnt(new_nd.mnt, &parent_nd); detach_mnt(user_nd.mnt, &root_parent); attach_mnt(user_nd.mnt, &old_nd); /* mount old root on put_old */ attach_mnt(new_nd.mnt, &root_parent); /* mount new_root on / */ touch_namespace(current->namespace); spin_unlock(&vfsmount_lock); chroot_fs_refs(&user_nd, &new_nd); security_sb_post_pivotroot(&user_nd, &new_nd); error = 0; path_release(&root_parent); path_release(&parent_nd); out2: mutex_unlock(&old_nd.dentry->d_inode->i_mutex); up_write(&namespace_sem); path_release(&user_nd); path_release(&old_nd); out1: path_release(&new_nd); out0: unlock_kernel(); return error; out3: spin_unlock(&vfsmount_lock); goto out2; } static void __init init_mount_tree(void) { struct vfsmount *mnt; struct namespace *namespace; struct task_struct *g, *p; mnt = do_kern_mount("rootfs", 0, "rootfs", NULL); if (IS_ERR(mnt)) panic("Can't create rootfs"); namespace = kmalloc(sizeof(*namespace), GFP_KERNEL); if (!namespace) panic("Can't allocate initial namespace"); atomic_set(&namespace->count, 1); INIT_LIST_HEAD(&namespace->list); init_waitqueue_head(&namespace->poll); namespace->event = 0; list_add(&mnt->mnt_list, &namespace->list); namespace->root = mnt; mnt->mnt_namespace = namespace; init_task.namespace = namespace; read_lock(&tasklist_lock); do_each_thread(g, p) { get_namespace(namespace); p->namespace = namespace; } while_each_thread(g, p); read_unlock(&tasklist_lock); set_fs_pwd(current->fs, namespace->root, namespace->root->mnt_root); set_fs_root(current->fs, namespace->root, namespace->root->mnt_root); } void __init mnt_init(unsigned long mempages) { struct list_head *d; unsigned int nr_hash; int i; init_rwsem(&namespace_sem); mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct vfsmount), 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL, NULL); mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC); if (!mount_hashtable) panic("Failed to allocate mount hash table\n"); /* * Find the power-of-two list-heads that can fit into the allocation.. * We don't guarantee that "sizeof(struct list_head)" is necessarily * a power-of-two. */ nr_hash = PAGE_SIZE / sizeof(struct list_head); hash_bits = 0; do { hash_bits++; } while ((nr_hash >> hash_bits) != 0); hash_bits--; /* * Re-calculate the actual number of entries and the mask * from the number of bits we can fit. */ nr_hash = 1UL << hash_bits; hash_mask = nr_hash - 1; printk("Mount-cache hash table entries: %d\n", nr_hash); /* And initialize the newly allocated array */ d = mount_hashtable; i = nr_hash; do { INIT_LIST_HEAD(d); d++; i--; } while (i); sysfs_init(); subsystem_register(&fs_subsys); init_rootfs(); init_mount_tree(); } void __put_namespace(struct namespace *namespace) { struct vfsmount *root = namespace->root; LIST_HEAD(umount_list); namespace->root = NULL; spin_unlock(&vfsmount_lock); down_write(&namespace_sem); spin_lock(&vfsmount_lock); umount_tree(root, 0, &umount_list); spin_unlock(&vfsmount_lock); up_write(&namespace_sem); release_mounts(&umount_list); kfree(namespace); }