/* * * 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 { unsigned int len; unsigned int type; u64 ino; struct list_head l_node; struct rb_node node; struct ovl_cache_entry *next_maybe_whiteout; bool is_whiteout; char name[]; }; struct ovl_dir_cache { long refcount; u64 version; struct list_head entries; }; struct ovl_readdir_data { struct dir_context ctx; bool is_merge; struct rb_root root; struct list_head *list; struct list_head middle; struct ovl_cache_entry *first_maybe_whiteout; int count; int err; }; struct ovl_dir_file { bool is_real; bool is_upper; struct ovl_dir_cache *cache; struct list_head *cursor; struct file *realfile; struct file *upperfile; }; 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(struct ovl_readdir_data *rdd, const char *name, int len, u64 ino, unsigned int d_type) { struct ovl_cache_entry *p; size_t size = offsetof(struct ovl_cache_entry, name[len + 1]); p = kmalloc(size, GFP_KERNEL); if (!p) return NULL; memcpy(p->name, name, len); p->name[len] = '\0'; p->len = len; p->type = d_type; p->ino = ino; p->is_whiteout = false; if (d_type == DT_CHR) { p->next_maybe_whiteout = rdd->first_maybe_whiteout; rdd->first_maybe_whiteout = p; } 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(rdd, 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(struct ovl_readdir_data *rdd, const char *name, int namelen, loff_t offset, u64 ino, unsigned int d_type) { struct ovl_cache_entry *p; 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(rdd, name, namelen, ino, d_type); if (p == NULL) rdd->err = -ENOMEM; else list_add_tail(&p->l_node, &rdd->middle); } return rdd->err; } 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 void ovl_cache_put(struct ovl_dir_file *od, struct dentry *dentry) { struct ovl_dir_cache *cache = od->cache; WARN_ON(cache->refcount <= 0); cache->refcount--; if (!cache->refcount) { if (ovl_dir_cache(dentry) == cache) ovl_set_dir_cache(dentry, NULL); ovl_cache_free(&cache->entries); kfree(cache); } } static int ovl_fill_merge(struct dir_context *ctx, const char *name, int namelen, loff_t offset, u64 ino, unsigned int d_type) { struct ovl_readdir_data *rdd = container_of(ctx, struct ovl_readdir_data, ctx); rdd->count++; if (!rdd->is_merge) return ovl_cache_entry_add_rb(rdd, name, namelen, ino, d_type); else return ovl_fill_lower(rdd, name, namelen, offset, ino, d_type); } static int ovl_check_whiteouts(struct dentry *dir, struct ovl_readdir_data *rdd) { int err; struct ovl_cache_entry *p; struct dentry *dentry; const struct cred *old_cred; struct cred *override_cred; override_cred = prepare_creds(); if (!override_cred) return -ENOMEM; /* * CAP_DAC_OVERRIDE for lookup */ cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE); old_cred = override_creds(override_cred); err = mutex_lock_killable(&dir->d_inode->i_mutex); if (!err) { while (rdd->first_maybe_whiteout) { p = rdd->first_maybe_whiteout; rdd->first_maybe_whiteout = p->next_maybe_whiteout; dentry = lookup_one_len(p->name, dir, p->len); if (!IS_ERR(dentry)) { p->is_whiteout = ovl_is_whiteout(dentry); dput(dentry); } } mutex_unlock(&dir->d_inode->i_mutex); } revert_creds(old_cred); put_cred(override_cred); return err; } static inline int ovl_dir_read(struct path *realpath, struct ovl_readdir_data *rdd) { struct file *realfile; int err; realfile = ovl_path_open(realpath, O_RDONLY | O_DIRECTORY); if (IS_ERR(realfile)) return PTR_ERR(realfile); rdd->first_maybe_whiteout = NULL; rdd->ctx.pos = 0; do { rdd->count = 0; rdd->err = 0; err = iterate_dir(realfile, &rdd->ctx); if (err >= 0) err = rdd->err; } while (!err && rdd->count); if (!err && rdd->first_maybe_whiteout) err = ovl_check_whiteouts(realpath->dentry, rdd); fput(realfile); return err; } static void ovl_dir_reset(struct file *file) { struct ovl_dir_file *od = file->private_data; struct ovl_dir_cache *cache = od->cache; struct dentry *dentry = file->f_path.dentry; enum ovl_path_type type = ovl_path_type(dentry); if (cache && ovl_dentry_version_get(dentry) != cache->version) { ovl_cache_put(od, dentry); od->cache = NULL; od->cursor = NULL; } WARN_ON(!od->is_real && !OVL_TYPE_MERGE(type)); if (od->is_real && OVL_TYPE_MERGE(type)) od->is_real = false; } static int ovl_dir_read_merged(struct dentry *dentry, struct list_head *list) { int err; struct path realpath; struct ovl_readdir_data rdd = { .ctx.actor = ovl_fill_merge, .list = list, .root = RB_ROOT, .is_merge = false, }; int idx, next; for (idx = 0; idx != -1; idx = next) { next = ovl_path_next(idx, dentry, &realpath); if (next != -1) { err = ovl_dir_read(&realpath, &rdd); if (err) break; } else { /* * Insert lowest layer entries before upper ones, this * allows offsets to be reasonably constant */ list_add(&rdd.middle, rdd.list); rdd.is_merge = true; err = ovl_dir_read(&realpath, &rdd); list_del(&rdd.middle); } } return err; } static void ovl_seek_cursor(struct ovl_dir_file *od, loff_t pos) { struct list_head *p; loff_t off = 0; list_for_each(p, &od->cache->entries) { if (off >= pos) break; off++; } /* Cursor is safe since the cache is stable */ od->cursor = p; } static struct ovl_dir_cache *ovl_cache_get(struct dentry *dentry) { int res; struct ovl_dir_cache *cache; cache = ovl_dir_cache(dentry); if (cache && ovl_dentry_version_get(dentry) == cache->version) { cache->refcount++; return cache; } ovl_set_dir_cache(dentry, NULL); cache = kzalloc(sizeof(struct ovl_dir_cache), GFP_KERNEL); if (!cache) return ERR_PTR(-ENOMEM); cache->refcount = 1; INIT_LIST_HEAD(&cache->entries); res = ovl_dir_read_merged(dentry, &cache->entries); if (res) { ovl_cache_free(&cache->entries); kfree(cache); return ERR_PTR(res); } cache->version = ovl_dentry_version_get(dentry); ovl_set_dir_cache(dentry, cache); return cache; } static int ovl_iterate(struct file *file, struct dir_context *ctx) { struct ovl_dir_file *od = file->private_data; struct dentry *dentry = file->f_path.dentry; struct ovl_cache_entry *p; if (!ctx->pos) ovl_dir_reset(file); if (od->is_real) return iterate_dir(od->realfile, ctx); if (!od->cache) { struct ovl_dir_cache *cache; cache = ovl_cache_get(dentry); if (IS_ERR(cache)) return PTR_ERR(cache); od->cache = cache; ovl_seek_cursor(od, ctx->pos); } while (od->cursor != &od->cache->entries) { p = list_entry(od->cursor, struct ovl_cache_entry, l_node); if (!p->is_whiteout) if (!dir_emit(ctx, p->name, p->len, p->ino, p->type)) break; od->cursor = p->l_node.next; ctx->pos++; } 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_inode(file)->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->cache) ovl_seek_cursor(od, offset); } res = offset; } out_unlock: mutex_unlock(&file_inode(file)->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; struct dentry *dentry = file->f_path.dentry; struct file *realfile = od->realfile; /* * Need to check if we started out being a lower dir, but got copied up */ if (!od->is_upper && OVL_TYPE_UPPER(ovl_path_type(dentry))) { struct inode *inode = file_inode(file); realfile = lockless_dereference(od->upperfile); if (!realfile) { struct path upperpath; ovl_path_upper(dentry, &upperpath); realfile = ovl_path_open(&upperpath, O_RDONLY); smp_mb__before_spinlock(); mutex_lock(&inode->i_mutex); if (!od->upperfile) { if (IS_ERR(realfile)) { mutex_unlock(&inode->i_mutex); return PTR_ERR(realfile); } od->upperfile = realfile; } else { /* somebody has beaten us to it */ if (!IS_ERR(realfile)) fput(realfile); realfile = od->upperfile; } mutex_unlock(&inode->i_mutex); } } return vfs_fsync_range(realfile, start, end, datasync); } static int ovl_dir_release(struct inode *inode, struct file *file) { struct ovl_dir_file *od = file->private_data; if (od->cache) { mutex_lock(&inode->i_mutex); ovl_cache_put(od, file->f_path.dentry); mutex_unlock(&inode->i_mutex); } fput(od->realfile); if (od->upperfile) fput(od->upperfile); 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); } od->realfile = realfile; od->is_real = !OVL_TYPE_MERGE(type); od->is_upper = OVL_TYPE_UPPER(type); file->private_data = od; return 0; } const struct file_operations ovl_dir_operations = { .read = generic_read_dir, .open = ovl_dir_open, .iterate = ovl_iterate, .llseek = ovl_dir_llseek, .fsync = ovl_dir_fsync, .release = ovl_dir_release, }; int ovl_check_empty_dir(struct dentry *dentry, struct list_head *list) { int err; struct ovl_cache_entry *p; err = ovl_dir_read_merged(dentry, list); 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; } void ovl_cleanup_whiteouts(struct dentry *upper, struct list_head *list) { struct ovl_cache_entry *p; mutex_lock_nested(&upper->d_inode->i_mutex, I_MUTEX_CHILD); list_for_each_entry(p, list, l_node) { struct dentry *dentry; if (!p->is_whiteout) continue; dentry = lookup_one_len(p->name, upper, p->len); if (IS_ERR(dentry)) { pr_err("overlayfs: lookup '%s/%.*s' failed (%i)\n", upper->d_name.name, p->len, p->name, (int) PTR_ERR(dentry)); continue; } ovl_cleanup(upper->d_inode, dentry); dput(dentry); } mutex_unlock(&upper->d_inode->i_mutex); }