/* * 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/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> 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 struct list_head *mount_hashtable; static int hash_mask, hash_bits; static kmem_cache_t *mnt_cache; 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_fslink); 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); } /* * Now, lookup_mnt increments the ref count before returning * the vfsmount struct. */ struct vfsmount *lookup_mnt(struct vfsmount *mnt, struct dentry *dentry) { struct list_head * head = mount_hashtable + hash(mnt, dentry); struct list_head * tmp = head; struct vfsmount *p, *found = NULL; spin_lock(&vfsmount_lock); for (;;) { tmp = tmp->next; p = NULL; if (tmp == head) break; p = list_entry(tmp, struct vfsmount, mnt_hash); if (p->mnt_parent == mnt && p->mnt_mountpoint == dentry) { found = mntget(p); break; } } spin_unlock(&vfsmount_lock); return found; } static inline int check_mnt(struct vfsmount *mnt) { return mnt->mnt_namespace == current->namespace; } 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--; } static void attach_mnt(struct vfsmount *mnt, struct nameidata *nd) { mnt->mnt_parent = mntget(nd->mnt); mnt->mnt_mountpoint = dget(nd->dentry); list_add(&mnt->mnt_hash, mount_hashtable+hash(nd->mnt, nd->dentry)); list_add_tail(&mnt->mnt_child, &nd->mnt->mnt_mounts); nd->dentry->d_mounted++; } 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 * clone_mnt(struct vfsmount *old, struct dentry *root) { 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; mnt->mnt_namespace = old->mnt_namespace; /* stick the duplicate mount on the same expiry list * as the original if that was on one */ spin_lock(&vfsmount_lock); if (!list_empty(&old->mnt_fslink)) list_add(&mnt->mnt_fslink, &old->mnt_fslink); spin_unlock(&vfsmount_lock); } return mnt; } void __mntput(struct vfsmount *mnt) { struct super_block *sb = mnt->mnt_sb; dput(mnt->mnt_root); free_vfsmnt(mnt); deactivate_super(sb); } EXPORT_SYMBOL(__mntput); /* 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(&n->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) { struct namespace *n = m->private; up_read(&n->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" }, { MS_NOATIME, ",noatime" }, { MS_NODIRATIME, ",nodiratime" }, { 0, NULL } }; static struct proc_fs_info mnt_info[] = { { MNT_NOSUID, ",nosuid" }, { MNT_NODEV, ",nodev" }, { MNT_NOEXEC, ",noexec" }, { 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) { struct list_head *next; struct vfsmount *this_parent = mnt; int actual_refs; int minimum_refs; spin_lock(&vfsmount_lock); actual_refs = atomic_read(&mnt->mnt_count); minimum_refs = 2; repeat: next = this_parent->mnt_mounts.next; resume: while (next != &this_parent->mnt_mounts) { struct vfsmount *p = list_entry(next, struct vfsmount, mnt_child); next = next->next; actual_refs += atomic_read(&p->mnt_count); minimum_refs += 2; if (!list_empty(&p->mnt_mounts)) { this_parent = p; goto repeat; } } if (this_parent != mnt) { next = this_parent->mnt_child.next; this_parent = this_parent->mnt_parent; goto resume; } 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) { if (atomic_read(&mnt->mnt_count) > 2) return -EBUSY; return 0; } EXPORT_SYMBOL(may_umount); void umount_tree(struct vfsmount *mnt) { struct vfsmount *p; LIST_HEAD(kill); for (p = mnt; p; p = next_mnt(p, mnt)) { list_del(&p->mnt_list); list_add(&p->mnt_list, &kill); } while (!list_empty(&kill)) { mnt = list_entry(kill.next, struct vfsmount, mnt_list); list_del_init(&mnt->mnt_list); list_del_init(&mnt->mnt_fslink); if (mnt->mnt_parent == mnt) { spin_unlock(&vfsmount_lock); } else { struct nameidata old_nd; detach_mnt(mnt, &old_nd); spin_unlock(&vfsmount_lock); path_release(&old_nd); } mntput(mnt); spin_lock(&vfsmount_lock); } } static int do_umount(struct vfsmount *mnt, int flags) { struct super_block * sb = mnt->mnt_sb; int retval; 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(¤t->namespace->sem); spin_lock(&vfsmount_lock); if (atomic_read(&sb->s_active) == 1) { /* last instance - try to be smart */ spin_unlock(&vfsmount_lock); lock_kernel(); DQUOT_OFF(sb); acct_auto_close(sb); unlock_kernel(); security_sb_umount_close(mnt); spin_lock(&vfsmount_lock); } retval = -EBUSY; if (atomic_read(&mnt->mnt_count) == 2 || flags & MNT_DETACH) { if (!list_empty(&mnt->mnt_list)) umount_tree(mnt); retval = 0; } spin_unlock(&vfsmount_lock); if (retval) security_sb_umount_busy(mnt); up_write(¤t->namespace->sem); 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 (permission(nd->dentry->d_inode, MAY_WRITE, nd)) 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; } } static struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry) { struct vfsmount *res, *p, *q, *r, *s; struct list_head *h; struct nameidata nd; res = q = clone_mnt(mnt, dentry); if (!q) goto Enomem; q->mnt_mountpoint = mnt->mnt_mountpoint; p = mnt; for (h = mnt->mnt_mounts.next; h != &mnt->mnt_mounts; h = h->next) { r = list_entry(h, struct vfsmount, mnt_child); if (!lives_below_in_same_fs(r->mnt_mountpoint, dentry)) continue; for (s = r; s; s = next_mnt(s, r)) { 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); 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) { spin_lock(&vfsmount_lock); umount_tree(res); spin_unlock(&vfsmount_lock); } return NULL; } 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; down(&nd->dentry->d_inode->i_sem); if (IS_DEADDIR(nd->dentry->d_inode)) goto out_unlock; err = security_sb_check_sb(mnt, nd); if (err) goto out_unlock; err = -ENOENT; spin_lock(&vfsmount_lock); if (IS_ROOT(nd->dentry) || !d_unhashed(nd->dentry)) { struct list_head head; attach_mnt(mnt, nd); list_add_tail(&head, &mnt->mnt_list); list_splice(&head, current->namespace->list.prev); mntget(mnt); err = 0; } spin_unlock(&vfsmount_lock); out_unlock: up(&nd->dentry->d_inode->i_sem); if (!err) security_sb_post_addmount(mnt, nd); return err; } /* * 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(¤t->namespace->sem); err = -EINVAL; if (check_mnt(nd->mnt) && (!recurse || check_mnt(old_nd.mnt))) { err = -ENOMEM; if (recurse) mnt = copy_tree(old_nd.mnt, old_nd.dentry); else mnt = clone_mnt(old_nd.mnt, old_nd.dentry); } if (mnt) { /* stop bind mounts from expiring */ spin_lock(&vfsmount_lock); list_del_init(&mnt->mnt_fslink); spin_unlock(&vfsmount_lock); err = graft_tree(mnt, nd); if (err) { spin_lock(&vfsmount_lock); umount_tree(mnt); spin_unlock(&vfsmount_lock); } else mntput(mnt); } up_write(¤t->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 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(¤t->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; down(&nd->dentry->d_inode->i_sem); if (IS_DEADDIR(nd->dentry->d_inode)) goto out1; spin_lock(&vfsmount_lock); if (!IS_ROOT(nd->dentry) && d_unhashed(nd->dentry)) goto out2; err = -EINVAL; if (old_nd.dentry != old_nd.mnt->mnt_root) goto out2; if (old_nd.mnt == old_nd.mnt->mnt_parent) goto out2; if (S_ISDIR(nd->dentry->d_inode->i_mode) != S_ISDIR(old_nd.dentry->d_inode->i_mode)) goto out2; err = -ELOOP; for (p = nd->mnt; p->mnt_parent!=p; p = p->mnt_parent) if (p == old_nd.mnt) goto out2; err = 0; detach_mnt(old_nd.mnt, &parent_nd); attach_mnt(old_nd.mnt, nd); /* if the mount is moved, it should no longer be expire * automatically */ list_del_init(&old_nd.mnt->mnt_fslink); out2: spin_unlock(&vfsmount_lock); out1: up(&nd->dentry->d_inode->i_sem); out: up_write(¤t->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(¤t->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; err = graft_tree(newmnt, nd); if (err == 0 && fslist) { /* add to the specified expiration list */ spin_lock(&vfsmount_lock); list_add_tail(&newmnt->mnt_fslink, fslist); spin_unlock(&vfsmount_lock); } unlock: up_write(¤t->namespace->sem); mntput(newmnt); return err; } EXPORT_SYMBOL_GPL(do_add_mount); /* * 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_fslink) { if (!xchg(&mnt->mnt_expiry_mark, 1) || atomic_read(&mnt->mnt_count) != 1) continue; mntget(mnt); list_move(&mnt->mnt_fslink, &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)) { mnt = list_entry(graveyard.next, struct vfsmount, mnt_fslink); list_del_init(&mnt->mnt_fslink); /* don't do anything if the namespace is dead - all the * vfsmounts from it are going away anyway */ namespace = mnt->mnt_namespace; if (!namespace || atomic_read(&namespace->count) <= 0) continue; get_namespace(namespace); spin_unlock(&vfsmount_lock); down_write(&namespace->sem); spin_lock(&vfsmount_lock); /* check that it is still dead: the count should now be 2 - as * contributed by the vfsmount parent and the mntget above */ if (atomic_read(&mnt->mnt_count) == 2) { struct vfsmount *xdmnt; struct dentry *xdentry; /* delete from the namespace */ list_del_init(&mnt->mnt_list); list_del_init(&mnt->mnt_child); list_del_init(&mnt->mnt_hash); mnt->mnt_mountpoint->d_mounted--; xdentry = mnt->mnt_mountpoint; mnt->mnt_mountpoint = mnt->mnt_root; xdmnt = mnt->mnt_parent; mnt->mnt_parent = mnt; spin_unlock(&vfsmount_lock); mntput(xdmnt); dput(xdentry); /* now lay it to rest if this was the last ref on the * superblock */ if (atomic_read(&mnt->mnt_sb->s_active) == 1) { /* last instance - try to be smart */ lock_kernel(); DQUOT_OFF(mnt->mnt_sb); acct_auto_close(mnt->mnt_sb); unlock_kernel(); } mntput(mnt); } 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_fslink, mounts); spin_unlock(&vfsmount_lock); } up_write(&namespace->sem); 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; flags &= ~(MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_ACTIVE); /* ... 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_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; } int copy_namespace(int flags, struct task_struct *tsk) { struct namespace *namespace = tsk->namespace; struct namespace *new_ns; struct vfsmount *rootmnt = NULL, *pwdmnt = NULL, *altrootmnt = NULL; struct fs_struct *fs = tsk->fs; struct vfsmount *p, *q; if (!namespace) return 0; get_namespace(namespace); if (!(flags & CLONE_NEWNS)) return 0; if (!capable(CAP_SYS_ADMIN)) { put_namespace(namespace); return -EPERM; } new_ns = kmalloc(sizeof(struct namespace), GFP_KERNEL); if (!new_ns) goto out; atomic_set(&new_ns->count, 1); init_rwsem(&new_ns->sem); INIT_LIST_HEAD(&new_ns->list); down_write(&tsk->namespace->sem); /* First pass: copy the tree topology */ new_ns->root = copy_tree(namespace->root, namespace->root->mnt_root); if (!new_ns->root) { up_write(&tsk->namespace->sem); kfree(new_ns); goto out; } 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(&tsk->namespace->sem); tsk->namespace = new_ns; if (rootmnt) mntput(rootmnt); if (pwdmnt) mntput(pwdmnt); if (altrootmnt) mntput(altrootmnt); put_namespace(namespace); return 0; out: put_namespace(namespace); return -ENOMEM; } 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. * * 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(¤t->namespace->sem); down(&old_nd.dentry->d_inode->i_sem); error = -EINVAL; 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 (new_nd.mnt->mnt_root != new_nd.dentry) goto out2; /* not a mountpoint */ 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 / */ 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: up(&old_nd.dentry->d_inode->i_sem); up_write(¤t->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_rwsem(&namespace->sem); 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; 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(); init_rootfs(); init_mount_tree(); } void __put_namespace(struct namespace *namespace) { struct vfsmount *mnt; down_write(&namespace->sem); spin_lock(&vfsmount_lock); list_for_each_entry(mnt, &namespace->list, mnt_list) { mnt->mnt_namespace = NULL; } umount_tree(namespace->root); spin_unlock(&vfsmount_lock); up_write(&namespace->sem); kfree(namespace); }