diff options
Diffstat (limited to 'fs/overlayfs/readdir.c')
| -rw-r--r-- | fs/overlayfs/readdir.c | 566 |
1 files changed, 566 insertions, 0 deletions
diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c new file mode 100644 index 00000000000..0797efbc7be --- /dev/null +++ b/fs/overlayfs/readdir.c @@ -0,0 +1,566 @@ +/* + * + * Copyright (C) 2011 Novell Inc. + * + * This program is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 as published by + * the Free Software Foundation. + */ + +#include <linux/fs.h> +#include <linux/slab.h> +#include <linux/namei.h> +#include <linux/file.h> +#include <linux/xattr.h> +#include <linux/rbtree.h> +#include <linux/security.h> +#include <linux/cred.h> +#include "overlayfs.h" + +struct ovl_cache_entry { + const char *name; + unsigned int len; + unsigned int type; + u64 ino; + bool is_whiteout; + struct list_head l_node; + struct rb_node node; +}; + +struct ovl_readdir_data { + struct rb_root *root; + struct list_head *list; + struct list_head *middle; + struct dentry *dir; + int count; + int err; +}; + +struct ovl_dir_file { + bool is_real; + bool is_cached; + struct list_head cursor; + u64 cache_version; + struct list_head cache; + struct file *realfile; +}; + +static struct ovl_cache_entry *ovl_cache_entry_from_node(struct rb_node *n) +{ + return container_of(n, struct ovl_cache_entry, node); +} + +static struct ovl_cache_entry *ovl_cache_entry_find(struct rb_root *root, + const char *name, int len) +{ + struct rb_node *node = root->rb_node; + int cmp; + + while (node) { + struct ovl_cache_entry *p = ovl_cache_entry_from_node(node); + + cmp = strncmp(name, p->name, len); + if (cmp > 0) + node = p->node.rb_right; + else if (cmp < 0 || len < p->len) + node = p->node.rb_left; + else + return p; + } + + return NULL; +} + +static struct ovl_cache_entry *ovl_cache_entry_new(const char *name, int len, + u64 ino, unsigned int d_type) +{ + struct ovl_cache_entry *p; + + p = kmalloc(sizeof(*p) + len + 1, GFP_KERNEL); + if (p) { + char *name_copy = (char *) (p + 1); + memcpy(name_copy, name, len); + name_copy[len] = '\0'; + p->name = name_copy; + p->len = len; + p->type = d_type; + p->ino = ino; + p->is_whiteout = false; + } + + return p; +} + +static int ovl_cache_entry_add_rb(struct ovl_readdir_data *rdd, + const char *name, int len, u64 ino, + unsigned int d_type) +{ + struct rb_node **newp = &rdd->root->rb_node; + struct rb_node *parent = NULL; + struct ovl_cache_entry *p; + + while (*newp) { + int cmp; + struct ovl_cache_entry *tmp; + + parent = *newp; + tmp = ovl_cache_entry_from_node(*newp); + cmp = strncmp(name, tmp->name, len); + if (cmp > 0) + newp = &tmp->node.rb_right; + else if (cmp < 0 || len < tmp->len) + newp = &tmp->node.rb_left; + else + return 0; + } + + p = ovl_cache_entry_new(name, len, ino, d_type); + if (p == NULL) + return -ENOMEM; + + list_add_tail(&p->l_node, rdd->list); + rb_link_node(&p->node, parent, newp); + rb_insert_color(&p->node, rdd->root); + + return 0; +} + +static int ovl_fill_lower(void *buf, const char *name, int namelen, + loff_t offset, u64 ino, unsigned int d_type) +{ + struct ovl_readdir_data *rdd = buf; + struct ovl_cache_entry *p; + + rdd->count++; + p = ovl_cache_entry_find(rdd->root, name, namelen); + if (p) { + list_move_tail(&p->l_node, rdd->middle); + } else { + p = ovl_cache_entry_new(name, namelen, ino, d_type); + if (p == NULL) + rdd->err = -ENOMEM; + else + list_add_tail(&p->l_node, rdd->middle); + } + + return rdd->err; +} + +static void ovl_cache_free(struct list_head *list) +{ + struct ovl_cache_entry *p; + struct ovl_cache_entry *n; + + list_for_each_entry_safe(p, n, list, l_node) + kfree(p); + + INIT_LIST_HEAD(list); +} + +static int ovl_fill_upper(void *buf, const char *name, int namelen, + loff_t offset, u64 ino, unsigned int d_type) +{ + struct ovl_readdir_data *rdd = buf; + + rdd->count++; + return ovl_cache_entry_add_rb(rdd, name, namelen, ino, d_type); +} + +static inline int ovl_dir_read(struct path *realpath, + struct ovl_readdir_data *rdd, filldir_t filler) +{ + struct file *realfile; + int err; + + realfile = ovl_path_open(realpath, O_RDONLY | O_DIRECTORY); + if (IS_ERR(realfile)) + return PTR_ERR(realfile); + + do { + rdd->count = 0; + rdd->err = 0; + err = vfs_readdir(realfile, filler, rdd); + if (err >= 0) + err = rdd->err; + } while (!err && rdd->count); + fput(realfile); + + return 0; +} + +static void ovl_dir_reset(struct file *file) +{ + struct ovl_dir_file *od = file->private_data; + enum ovl_path_type type = ovl_path_type(file->f_path.dentry); + + if (ovl_dentry_version_get(file->f_path.dentry) != od->cache_version) { + list_del_init(&od->cursor); + ovl_cache_free(&od->cache); + od->is_cached = false; + } + WARN_ON(!od->is_real && type != OVL_PATH_MERGE); + if (od->is_real && type == OVL_PATH_MERGE) { + fput(od->realfile); + od->realfile = NULL; + od->is_real = false; + } +} + +static int ovl_dir_mark_whiteouts(struct ovl_readdir_data *rdd) +{ + struct ovl_cache_entry *p; + struct dentry *dentry; + const struct cred *old_cred; + struct cred *override_cred; + + override_cred = prepare_creds(); + if (!override_cred) { + ovl_cache_free(rdd->list); + return -ENOMEM; + } + + /* + * CAP_SYS_ADMIN for getxattr + * CAP_DAC_OVERRIDE for lookup + */ + cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN); + cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE); + old_cred = override_creds(override_cred); + + mutex_lock(&rdd->dir->d_inode->i_mutex); + list_for_each_entry(p, rdd->list, l_node) { + if (p->type != DT_LNK) + continue; + + dentry = lookup_one_len(p->name, rdd->dir, p->len); + if (IS_ERR(dentry)) + continue; + + p->is_whiteout = ovl_is_whiteout(dentry); + dput(dentry); + } + mutex_unlock(&rdd->dir->d_inode->i_mutex); + + revert_creds(old_cred); + put_cred(override_cred); + + return 0; +} + +static inline int ovl_dir_read_merged(struct path *upperpath, + struct path *lowerpath, + struct ovl_readdir_data *rdd) +{ + int err; + struct rb_root root = RB_ROOT; + struct list_head middle; + + rdd->root = &root; + if (upperpath->dentry) { + rdd->dir = upperpath->dentry; + err = ovl_dir_read(upperpath, rdd, ovl_fill_upper); + if (err) + goto out; + + err = ovl_dir_mark_whiteouts(rdd); + if (err) + goto out; + } + /* + * Insert lowerpath entries before upperpath ones, this allows + * offsets to be reasonably constant + */ + list_add(&middle, rdd->list); + rdd->middle = &middle; + err = ovl_dir_read(lowerpath, rdd, ovl_fill_lower); + list_del(&middle); +out: + rdd->root = NULL; + + return err; +} + +static void ovl_seek_cursor(struct ovl_dir_file *od, loff_t pos) +{ + struct list_head *l; + loff_t off; + + l = od->cache.next; + for (off = 0; off < pos; off++) { + if (l == &od->cache) + break; + l = l->next; + } + list_move_tail(&od->cursor, l); +} + +static int ovl_readdir(struct file *file, void *buf, filldir_t filler) +{ + struct ovl_dir_file *od = file->private_data; + int res; + + if (!file->f_pos) + ovl_dir_reset(file); + + if (od->is_real) { + res = vfs_readdir(od->realfile, filler, buf); + file->f_pos = od->realfile->f_pos; + + return res; + } + + if (!od->is_cached) { + struct path lowerpath; + struct path upperpath; + struct ovl_readdir_data rdd = { .list = &od->cache }; + + ovl_path_lower(file->f_path.dentry, &lowerpath); + ovl_path_upper(file->f_path.dentry, &upperpath); + + res = ovl_dir_read_merged(&upperpath, &lowerpath, &rdd); + if (res) { + ovl_cache_free(rdd.list); + return res; + } + + od->cache_version = ovl_dentry_version_get(file->f_path.dentry); + od->is_cached = true; + + ovl_seek_cursor(od, file->f_pos); + } + + while (od->cursor.next != &od->cache) { + int over; + loff_t off; + struct ovl_cache_entry *p; + + p = list_entry(od->cursor.next, struct ovl_cache_entry, l_node); + off = file->f_pos; + if (!p->is_whiteout) { + over = filler(buf, p->name, p->len, off, p->ino, + p->type); + if (over) + break; + } + file->f_pos++; + list_move(&od->cursor, &p->l_node); + } + + return 0; +} + +static loff_t ovl_dir_llseek(struct file *file, loff_t offset, int origin) +{ + loff_t res; + struct ovl_dir_file *od = file->private_data; + + mutex_lock(&file->f_dentry->d_inode->i_mutex); + if (!file->f_pos) + ovl_dir_reset(file); + + if (od->is_real) { + res = vfs_llseek(od->realfile, offset, origin); + file->f_pos = od->realfile->f_pos; + } else { + res = -EINVAL; + + switch (origin) { + case SEEK_CUR: + offset += file->f_pos; + break; + case SEEK_SET: + break; + default: + goto out_unlock; + } + if (offset < 0) + goto out_unlock; + + if (offset != file->f_pos) { + file->f_pos = offset; + if (od->is_cached) + ovl_seek_cursor(od, offset); + } + res = offset; + } +out_unlock: + mutex_unlock(&file->f_dentry->d_inode->i_mutex); + + return res; +} + +static int ovl_dir_fsync(struct file *file, loff_t start, loff_t end, + int datasync) +{ + struct ovl_dir_file *od = file->private_data; + + /* May need to reopen directory if it got copied up */ + if (!od->realfile) { + struct path upperpath; + + ovl_path_upper(file->f_path.dentry, &upperpath); + od->realfile = ovl_path_open(&upperpath, O_RDONLY); + if (IS_ERR(od->realfile)) + return PTR_ERR(od->realfile); + } + + return vfs_fsync_range(od->realfile, start, end, datasync); +} + +static int ovl_dir_release(struct inode *inode, struct file *file) +{ + struct ovl_dir_file *od = file->private_data; + + list_del(&od->cursor); + ovl_cache_free(&od->cache); + if (od->realfile) + fput(od->realfile); + kfree(od); + + return 0; +} + +static int ovl_dir_open(struct inode *inode, struct file *file) +{ + struct path realpath; + struct file *realfile; + struct ovl_dir_file *od; + enum ovl_path_type type; + + od = kzalloc(sizeof(struct ovl_dir_file), GFP_KERNEL); + if (!od) + return -ENOMEM; + + type = ovl_path_real(file->f_path.dentry, &realpath); + realfile = ovl_path_open(&realpath, file->f_flags); + if (IS_ERR(realfile)) { + kfree(od); + return PTR_ERR(realfile); + } + INIT_LIST_HEAD(&od->cache); + INIT_LIST_HEAD(&od->cursor); + od->is_cached = false; + od->realfile = realfile; + od->is_real = (type != OVL_PATH_MERGE); + file->private_data = od; + + return 0; +} + +const struct file_operations ovl_dir_operations = { + .read = generic_read_dir, + .open = ovl_dir_open, + .readdir = ovl_readdir, + .llseek = ovl_dir_llseek, + .fsync = ovl_dir_fsync, + .release = ovl_dir_release, +}; + +static int ovl_check_empty_dir(struct dentry *dentry, struct list_head *list) +{ + int err; + struct path lowerpath; + struct path upperpath; + struct ovl_cache_entry *p; + struct ovl_readdir_data rdd = { .list = list }; + + ovl_path_upper(dentry, &upperpath); + ovl_path_lower(dentry, &lowerpath); + + err = ovl_dir_read_merged(&upperpath, &lowerpath, &rdd); + if (err) + return err; + + err = 0; + + list_for_each_entry(p, list, l_node) { + if (p->is_whiteout) + continue; + + if (p->name[0] == '.') { + if (p->len == 1) + continue; + if (p->len == 2 && p->name[1] == '.') + continue; + } + err = -ENOTEMPTY; + break; + } + + return err; +} + +static int ovl_remove_whiteouts(struct dentry *dir, struct list_head *list) +{ + struct path upperpath; + struct dentry *upperdir; + struct ovl_cache_entry *p; + const struct cred *old_cred; + struct cred *override_cred; + int err; + + ovl_path_upper(dir, &upperpath); + upperdir = upperpath.dentry; + + override_cred = prepare_creds(); + if (!override_cred) + return -ENOMEM; + + /* + * CAP_DAC_OVERRIDE for lookup and unlink + * CAP_SYS_ADMIN for setxattr of "trusted" namespace + * CAP_FOWNER for unlink in sticky directory + */ + cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE); + cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN); + cap_raise(override_cred->cap_effective, CAP_FOWNER); + old_cred = override_creds(override_cred); + + err = vfs_setxattr(upperdir, ovl_opaque_xattr, "y", 1, 0); + if (err) + goto out_revert_creds; + + mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT); + list_for_each_entry(p, list, l_node) { + struct dentry *dentry; + int ret; + + if (!p->is_whiteout) + continue; + + dentry = lookup_one_len(p->name, upperdir, p->len); + if (IS_ERR(dentry)) { + printk(KERN_WARNING + "overlayfs: failed to lookup whiteout %.*s: %li\n", + p->len, p->name, PTR_ERR(dentry)); + continue; + } + ret = vfs_unlink(upperdir->d_inode, dentry); + dput(dentry); + if (ret) + printk(KERN_WARNING + "overlayfs: failed to unlink whiteout %.*s: %i\n", + p->len, p->name, ret); + } + mutex_unlock(&upperdir->d_inode->i_mutex); + +out_revert_creds: + revert_creds(old_cred); + put_cred(override_cred); + + return err; +} + +int ovl_check_empty_and_clear(struct dentry *dentry, enum ovl_path_type type) +{ + int err; + LIST_HEAD(list); + + err = ovl_check_empty_dir(dentry, &list); + if (!err && type == OVL_PATH_MERGE) + err = ovl_remove_whiteouts(dentry, &list); + + ovl_cache_free(&list); + + return err; +} |