diff options
Diffstat (limited to 'fs/namespace.c')
| -rw-r--r-- | fs/namespace.c | 1465 |
1 files changed, 1465 insertions, 0 deletions
diff --git a/fs/namespace.c b/fs/namespace.c new file mode 100644 index 000000000000..3b93e5d750eb --- /dev/null +++ b/fs/namespace.c @@ -0,0 +1,1465 @@ +/* + * 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); +} |
