/* * * 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 <uapi/linux/magic.h> #include <linux/fs.h> #include <linux/namei.h> #include <linux/xattr.h> #include <linux/mount.h> #include <linux/parser.h> #include <linux/module.h> #include <linux/statfs.h> #include <linux/seq_file.h> #include <linux/posix_acl_xattr.h> #include "overlayfs.h" MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>"); MODULE_DESCRIPTION("Overlay filesystem"); MODULE_LICENSE("GPL"); struct ovl_dir_cache; #define OVL_MAX_STACK 500 static bool ovl_redirect_dir_def = IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_DIR); module_param_named(redirect_dir, ovl_redirect_dir_def, bool, 0644); MODULE_PARM_DESC(ovl_redirect_dir_def, "Default to on or off for the redirect_dir feature"); static bool ovl_index_def = IS_ENABLED(CONFIG_OVERLAY_FS_INDEX); module_param_named(index, ovl_index_def, bool, 0644); MODULE_PARM_DESC(ovl_index_def, "Default to on or off for the inodes index feature"); static void ovl_entry_stack_free(struct ovl_entry *oe) { unsigned int i; for (i = 0; i < oe->numlower; i++) dput(oe->lowerstack[i].dentry); } static void ovl_dentry_release(struct dentry *dentry) { struct ovl_entry *oe = dentry->d_fsdata; if (oe) { ovl_entry_stack_free(oe); kfree_rcu(oe, rcu); } } static int ovl_check_append_only(struct inode *inode, int flag) { /* * This test was moot in vfs may_open() because overlay inode does * not have the S_APPEND flag, so re-check on real upper inode */ if (IS_APPEND(inode)) { if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND)) return -EPERM; if (flag & O_TRUNC) return -EPERM; } return 0; } static struct dentry *ovl_d_real(struct dentry *dentry, const struct inode *inode, unsigned int open_flags, unsigned int flags) { struct dentry *real; int err; if (flags & D_REAL_UPPER) return ovl_dentry_upper(dentry); if (!d_is_reg(dentry)) { if (!inode || inode == d_inode(dentry)) return dentry; goto bug; } if (open_flags) { err = ovl_open_maybe_copy_up(dentry, open_flags); if (err) return ERR_PTR(err); } real = ovl_dentry_upper(dentry); if (real && (!inode || inode == d_inode(real))) { if (!inode) { err = ovl_check_append_only(d_inode(real), open_flags); if (err) return ERR_PTR(err); } return real; } real = ovl_dentry_lower(dentry); if (!real) goto bug; /* Handle recursion */ real = d_real(real, inode, open_flags, 0); if (!inode || inode == d_inode(real)) return real; bug: WARN(1, "ovl_d_real(%pd4, %s:%lu): real dentry not found\n", dentry, inode ? inode->i_sb->s_id : "NULL", inode ? inode->i_ino : 0); return dentry; } static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags) { struct ovl_entry *oe = dentry->d_fsdata; unsigned int i; int ret = 1; for (i = 0; i < oe->numlower; i++) { struct dentry *d = oe->lowerstack[i].dentry; if (d->d_flags & DCACHE_OP_REVALIDATE) { ret = d->d_op->d_revalidate(d, flags); if (ret < 0) return ret; if (!ret) { if (!(flags & LOOKUP_RCU)) d_invalidate(d); return -ESTALE; } } } return 1; } static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags) { struct ovl_entry *oe = dentry->d_fsdata; unsigned int i; int ret = 1; for (i = 0; i < oe->numlower; i++) { struct dentry *d = oe->lowerstack[i].dentry; if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE) { ret = d->d_op->d_weak_revalidate(d, flags); if (ret <= 0) break; } } return ret; } static const struct dentry_operations ovl_dentry_operations = { .d_release = ovl_dentry_release, .d_real = ovl_d_real, }; static const struct dentry_operations ovl_reval_dentry_operations = { .d_release = ovl_dentry_release, .d_real = ovl_d_real, .d_revalidate = ovl_dentry_revalidate, .d_weak_revalidate = ovl_dentry_weak_revalidate, }; static struct kmem_cache *ovl_inode_cachep; static struct inode *ovl_alloc_inode(struct super_block *sb) { struct ovl_inode *oi = kmem_cache_alloc(ovl_inode_cachep, GFP_KERNEL); if (!oi) return NULL; oi->cache = NULL; oi->redirect = NULL; oi->version = 0; oi->flags = 0; oi->__upperdentry = NULL; oi->lower = NULL; mutex_init(&oi->lock); return &oi->vfs_inode; } static void ovl_i_callback(struct rcu_head *head) { struct inode *inode = container_of(head, struct inode, i_rcu); kmem_cache_free(ovl_inode_cachep, OVL_I(inode)); } static void ovl_destroy_inode(struct inode *inode) { struct ovl_inode *oi = OVL_I(inode); dput(oi->__upperdentry); kfree(oi->redirect); ovl_dir_cache_free(inode); mutex_destroy(&oi->lock); call_rcu(&inode->i_rcu, ovl_i_callback); } static void ovl_free_fs(struct ovl_fs *ofs) { unsigned i; dput(ofs->indexdir); dput(ofs->workdir); if (ofs->workdir_locked) ovl_inuse_unlock(ofs->workbasedir); dput(ofs->workbasedir); if (ofs->upperdir_locked) ovl_inuse_unlock(ofs->upper_mnt->mnt_root); mntput(ofs->upper_mnt); for (i = 0; i < ofs->numlower; i++) { mntput(ofs->lower_layers[i].mnt); free_anon_bdev(ofs->lower_layers[i].pseudo_dev); } kfree(ofs->lower_layers); kfree(ofs->config.lowerdir); kfree(ofs->config.upperdir); kfree(ofs->config.workdir); if (ofs->creator_cred) put_cred(ofs->creator_cred); kfree(ofs); } static void ovl_put_super(struct super_block *sb) { struct ovl_fs *ofs = sb->s_fs_info; ovl_free_fs(ofs); } static int ovl_sync_fs(struct super_block *sb, int wait) { struct ovl_fs *ofs = sb->s_fs_info; struct super_block *upper_sb; int ret; if (!ofs->upper_mnt) return 0; upper_sb = ofs->upper_mnt->mnt_sb; if (!upper_sb->s_op->sync_fs) return 0; /* real inodes have already been synced by sync_filesystem(ovl_sb) */ down_read(&upper_sb->s_umount); ret = upper_sb->s_op->sync_fs(upper_sb, wait); up_read(&upper_sb->s_umount); return ret; } /** * ovl_statfs * @sb: The overlayfs super block * @buf: The struct kstatfs to fill in with stats * * Get the filesystem statistics. As writes always target the upper layer * filesystem pass the statfs to the upper filesystem (if it exists) */ static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf) { struct ovl_fs *ofs = dentry->d_sb->s_fs_info; struct dentry *root_dentry = dentry->d_sb->s_root; struct path path; int err; ovl_path_real(root_dentry, &path); err = vfs_statfs(&path, buf); if (!err) { buf->f_namelen = ofs->namelen; buf->f_type = OVERLAYFS_SUPER_MAGIC; } return err; } /* Will this overlay be forced to mount/remount ro? */ static bool ovl_force_readonly(struct ovl_fs *ofs) { return (!ofs->upper_mnt || !ofs->workdir); } /** * ovl_show_options * * Prints the mount options for a given superblock. * Returns zero; does not fail. */ static int ovl_show_options(struct seq_file *m, struct dentry *dentry) { struct super_block *sb = dentry->d_sb; struct ovl_fs *ofs = sb->s_fs_info; seq_show_option(m, "lowerdir", ofs->config.lowerdir); if (ofs->config.upperdir) { seq_show_option(m, "upperdir", ofs->config.upperdir); seq_show_option(m, "workdir", ofs->config.workdir); } if (ofs->config.default_permissions) seq_puts(m, ",default_permissions"); if (ofs->config.redirect_dir != ovl_redirect_dir_def) seq_printf(m, ",redirect_dir=%s", ofs->config.redirect_dir ? "on" : "off"); if (ofs->config.index != ovl_index_def) seq_printf(m, ",index=%s", ofs->config.index ? "on" : "off"); return 0; } static int ovl_remount(struct super_block *sb, int *flags, char *data) { struct ovl_fs *ofs = sb->s_fs_info; if (!(*flags & MS_RDONLY) && ovl_force_readonly(ofs)) return -EROFS; return 0; } static const struct super_operations ovl_super_operations = { .alloc_inode = ovl_alloc_inode, .destroy_inode = ovl_destroy_inode, .drop_inode = generic_delete_inode, .put_super = ovl_put_super, .sync_fs = ovl_sync_fs, .statfs = ovl_statfs, .show_options = ovl_show_options, .remount_fs = ovl_remount, }; enum { OPT_LOWERDIR, OPT_UPPERDIR, OPT_WORKDIR, OPT_DEFAULT_PERMISSIONS, OPT_REDIRECT_DIR_ON, OPT_REDIRECT_DIR_OFF, OPT_INDEX_ON, OPT_INDEX_OFF, OPT_ERR, }; static const match_table_t ovl_tokens = { {OPT_LOWERDIR, "lowerdir=%s"}, {OPT_UPPERDIR, "upperdir=%s"}, {OPT_WORKDIR, "workdir=%s"}, {OPT_DEFAULT_PERMISSIONS, "default_permissions"}, {OPT_REDIRECT_DIR_ON, "redirect_dir=on"}, {OPT_REDIRECT_DIR_OFF, "redirect_dir=off"}, {OPT_INDEX_ON, "index=on"}, {OPT_INDEX_OFF, "index=off"}, {OPT_ERR, NULL} }; static char *ovl_next_opt(char **s) { char *sbegin = *s; char *p; if (sbegin == NULL) return NULL; for (p = sbegin; *p; p++) { if (*p == '\\') { p++; if (!*p) break; } else if (*p == ',') { *p = '\0'; *s = p + 1; return sbegin; } } *s = NULL; return sbegin; } static int ovl_parse_opt(char *opt, struct ovl_config *config) { char *p; while ((p = ovl_next_opt(&opt)) != NULL) { int token; substring_t args[MAX_OPT_ARGS]; if (!*p) continue; token = match_token(p, ovl_tokens, args); switch (token) { case OPT_UPPERDIR: kfree(config->upperdir); config->upperdir = match_strdup(&args[0]); if (!config->upperdir) return -ENOMEM; break; case OPT_LOWERDIR: kfree(config->lowerdir); config->lowerdir = match_strdup(&args[0]); if (!config->lowerdir) return -ENOMEM; break; case OPT_WORKDIR: kfree(config->workdir); config->workdir = match_strdup(&args[0]); if (!config->workdir) return -ENOMEM; break; case OPT_DEFAULT_PERMISSIONS: config->default_permissions = true; break; case OPT_REDIRECT_DIR_ON: config->redirect_dir = true; break; case OPT_REDIRECT_DIR_OFF: config->redirect_dir = false; break; case OPT_INDEX_ON: config->index = true; break; case OPT_INDEX_OFF: config->index = false; break; default: pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p); return -EINVAL; } } /* Workdir is useless in non-upper mount */ if (!config->upperdir && config->workdir) { pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n", config->workdir); kfree(config->workdir); config->workdir = NULL; } return 0; } #define OVL_WORKDIR_NAME "work" #define OVL_INDEXDIR_NAME "index" static struct dentry *ovl_workdir_create(struct ovl_fs *ofs, const char *name, bool persist) { struct inode *dir = ofs->workbasedir->d_inode; struct vfsmount *mnt = ofs->upper_mnt; struct dentry *work; int err; bool retried = false; bool locked = false; err = mnt_want_write(mnt); if (err) goto out_err; inode_lock_nested(dir, I_MUTEX_PARENT); locked = true; retry: work = lookup_one_len(name, ofs->workbasedir, strlen(name)); if (!IS_ERR(work)) { struct iattr attr = { .ia_valid = ATTR_MODE, .ia_mode = S_IFDIR | 0, }; if (work->d_inode) { err = -EEXIST; if (retried) goto out_dput; if (persist) goto out_unlock; retried = true; ovl_workdir_cleanup(dir, mnt, work, 0); dput(work); goto retry; } err = ovl_create_real(dir, work, &(struct cattr){.mode = S_IFDIR | 0}, NULL, true); if (err) goto out_dput; /* * Try to remove POSIX ACL xattrs from workdir. We are good if: * * a) success (there was a POSIX ACL xattr and was removed) * b) -ENODATA (there was no POSIX ACL xattr) * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported) * * There are various other error values that could effectively * mean that the xattr doesn't exist (e.g. -ERANGE is returned * if the xattr name is too long), but the set of filesystems * allowed as upper are limited to "normal" ones, where checking * for the above two errors is sufficient. */ err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT); if (err && err != -ENODATA && err != -EOPNOTSUPP) goto out_dput; err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS); if (err && err != -ENODATA && err != -EOPNOTSUPP) goto out_dput; /* Clear any inherited mode bits */ inode_lock(work->d_inode); err = notify_change(work, &attr, NULL); inode_unlock(work->d_inode); if (err) goto out_dput; } else { err = PTR_ERR(work); goto out_err; } out_unlock: mnt_drop_write(mnt); if (locked) inode_unlock(dir); return work; out_dput: dput(work); out_err: pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n", ofs->config.workdir, name, -err); work = NULL; goto out_unlock; } static void ovl_unescape(char *s) { char *d = s; for (;; s++, d++) { if (*s == '\\') s++; *d = *s; if (!*s) break; } } static int ovl_mount_dir_noesc(const char *name, struct path *path) { int err = -EINVAL; if (!*name) { pr_err("overlayfs: empty lowerdir\n"); goto out; } err = kern_path(name, LOOKUP_FOLLOW, path); if (err) { pr_err("overlayfs: failed to resolve '%s': %i\n", name, err); goto out; } err = -EINVAL; if (ovl_dentry_weird(path->dentry)) { pr_err("overlayfs: filesystem on '%s' not supported\n", name); goto out_put; } if (!d_is_dir(path->dentry)) { pr_err("overlayfs: '%s' not a directory\n", name); goto out_put; } return 0; out_put: path_put_init(path); out: return err; } static int ovl_mount_dir(const char *name, struct path *path) { int err = -ENOMEM; char *tmp = kstrdup(name, GFP_KERNEL); if (tmp) { ovl_unescape(tmp); err = ovl_mount_dir_noesc(tmp, path); if (!err) if (ovl_dentry_remote(path->dentry)) { pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n", tmp); path_put_init(path); err = -EINVAL; } kfree(tmp); } return err; } static int ovl_check_namelen(struct path *path, struct ovl_fs *ofs, const char *name) { struct kstatfs statfs; int err = vfs_statfs(path, &statfs); if (err) pr_err("overlayfs: statfs failed on '%s'\n", name); else ofs->namelen = max(ofs->namelen, statfs.f_namelen); return err; } static int ovl_lower_dir(const char *name, struct path *path, struct ovl_fs *ofs, int *stack_depth, bool *remote) { int err; err = ovl_mount_dir_noesc(name, path); if (err) goto out; err = ovl_check_namelen(path, ofs, name); if (err) goto out_put; *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth); if (ovl_dentry_remote(path->dentry)) *remote = true; /* * The inodes index feature needs to encode and decode file * handles, so it requires that all layers support them. */ if (ofs->config.index && !ovl_can_decode_fh(path->dentry->d_sb)) { ofs->config.index = false; pr_warn("overlayfs: fs on '%s' does not support file handles, falling back to index=off.\n", name); } return 0; out_put: path_put_init(path); out: return err; } /* Workdir should not be subdir of upperdir and vice versa */ static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir) { bool ok = false; if (workdir != upperdir) { ok = (lock_rename(workdir, upperdir) == NULL); unlock_rename(workdir, upperdir); } return ok; } static unsigned int ovl_split_lowerdirs(char *str) { unsigned int ctr = 1; char *s, *d; for (s = d = str;; s++, d++) { if (*s == '\\') { s++; } else if (*s == ':') { *d = '\0'; ctr++; continue; } *d = *s; if (!*s) break; } return ctr; } static int __maybe_unused ovl_posix_acl_xattr_get(const struct xattr_handler *handler, struct dentry *dentry, struct inode *inode, const char *name, void *buffer, size_t size) { return ovl_xattr_get(dentry, inode, handler->name, buffer, size); } static int __maybe_unused ovl_posix_acl_xattr_set(const struct xattr_handler *handler, struct dentry *dentry, struct inode *inode, const char *name, const void *value, size_t size, int flags) { struct dentry *workdir = ovl_workdir(dentry); struct inode *realinode = ovl_inode_real(inode); struct posix_acl *acl = NULL; int err; /* Check that everything is OK before copy-up */ if (value) { acl = posix_acl_from_xattr(&init_user_ns, value, size); if (IS_ERR(acl)) return PTR_ERR(acl); } err = -EOPNOTSUPP; if (!IS_POSIXACL(d_inode(workdir))) goto out_acl_release; if (!realinode->i_op->set_acl) goto out_acl_release; if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) { err = acl ? -EACCES : 0; goto out_acl_release; } err = -EPERM; if (!inode_owner_or_capable(inode)) goto out_acl_release; posix_acl_release(acl); /* * Check if sgid bit needs to be cleared (actual setacl operation will * be done with mounter's capabilities and so that won't do it for us). */ if (unlikely(inode->i_mode & S_ISGID) && handler->flags == ACL_TYPE_ACCESS && !in_group_p(inode->i_gid) && !capable_wrt_inode_uidgid(inode, CAP_FSETID)) { struct iattr iattr = { .ia_valid = ATTR_KILL_SGID }; err = ovl_setattr(dentry, &iattr); if (err) return err; } err = ovl_xattr_set(dentry, inode, handler->name, value, size, flags); if (!err) ovl_copyattr(ovl_inode_real(inode), inode); return err; out_acl_release: posix_acl_release(acl); return err; } static int ovl_own_xattr_get(const struct xattr_handler *handler, struct dentry *dentry, struct inode *inode, const char *name, void *buffer, size_t size) { return -EOPNOTSUPP; } static int ovl_own_xattr_set(const struct xattr_handler *handler, struct dentry *dentry, struct inode *inode, const char *name, const void *value, size_t size, int flags) { return -EOPNOTSUPP; } static int ovl_other_xattr_get(const struct xattr_handler *handler, struct dentry *dentry, struct inode *inode, const char *name, void *buffer, size_t size) { return ovl_xattr_get(dentry, inode, name, buffer, size); } static int ovl_other_xattr_set(const struct xattr_handler *handler, struct dentry *dentry, struct inode *inode, const char *name, const void *value, size_t size, int flags) { return ovl_xattr_set(dentry, inode, name, value, size, flags); } static const struct xattr_handler __maybe_unused ovl_posix_acl_access_xattr_handler = { .name = XATTR_NAME_POSIX_ACL_ACCESS, .flags = ACL_TYPE_ACCESS, .get = ovl_posix_acl_xattr_get, .set = ovl_posix_acl_xattr_set, }; static const struct xattr_handler __maybe_unused ovl_posix_acl_default_xattr_handler = { .name = XATTR_NAME_POSIX_ACL_DEFAULT, .flags = ACL_TYPE_DEFAULT, .get = ovl_posix_acl_xattr_get, .set = ovl_posix_acl_xattr_set, }; static const struct xattr_handler ovl_own_xattr_handler = { .prefix = OVL_XATTR_PREFIX, .get = ovl_own_xattr_get, .set = ovl_own_xattr_set, }; static const struct xattr_handler ovl_other_xattr_handler = { .prefix = "", /* catch all */ .get = ovl_other_xattr_get, .set = ovl_other_xattr_set, }; static const struct xattr_handler *ovl_xattr_handlers[] = { #ifdef CONFIG_FS_POSIX_ACL &ovl_posix_acl_access_xattr_handler, &ovl_posix_acl_default_xattr_handler, #endif &ovl_own_xattr_handler, &ovl_other_xattr_handler, NULL }; static int ovl_get_upper(struct ovl_fs *ofs, struct path *upperpath) { struct vfsmount *upper_mnt; int err; err = ovl_mount_dir(ofs->config.upperdir, upperpath); if (err) goto out; /* Upper fs should not be r/o */ if (sb_rdonly(upperpath->mnt->mnt_sb)) { pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n"); err = -EINVAL; goto out; } err = ovl_check_namelen(upperpath, ofs, ofs->config.upperdir); if (err) goto out; err = -EBUSY; if (ovl_inuse_trylock(upperpath->dentry)) { ofs->upperdir_locked = true; } else if (ofs->config.index) { pr_err("overlayfs: upperdir is in-use by another mount, mount with '-o index=off' to override exclusive upperdir protection.\n"); goto out; } else { pr_warn("overlayfs: upperdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n"); } upper_mnt = clone_private_mount(upperpath); err = PTR_ERR(upper_mnt); if (IS_ERR(upper_mnt)) { pr_err("overlayfs: failed to clone upperpath\n"); goto out; } /* Don't inherit atime flags */ upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME); ofs->upper_mnt = upper_mnt; err = 0; out: return err; } static int ovl_make_workdir(struct ovl_fs *ofs, struct path *workpath) { struct dentry *temp; int err; ofs->workdir = ovl_workdir_create(ofs, OVL_WORKDIR_NAME, false); if (!ofs->workdir) return 0; /* * Upper should support d_type, else whiteouts are visible. Given * workdir and upper are on same fs, we can do iterate_dir() on * workdir. This check requires successful creation of workdir in * previous step. */ err = ovl_check_d_type_supported(workpath); if (err < 0) return err; /* * We allowed this configuration and don't want to break users over * kernel upgrade. So warn instead of erroring out. */ if (!err) pr_warn("overlayfs: upper fs needs to support d_type.\n"); /* Check if upper/work fs supports O_TMPFILE */ temp = ovl_do_tmpfile(ofs->workdir, S_IFREG | 0); ofs->tmpfile = !IS_ERR(temp); if (ofs->tmpfile) dput(temp); else pr_warn("overlayfs: upper fs does not support tmpfile.\n"); /* * Check if upper/work fs supports trusted.overlay.* xattr */ err = ovl_do_setxattr(ofs->workdir, OVL_XATTR_OPAQUE, "0", 1, 0); if (err) { ofs->noxattr = true; pr_warn("overlayfs: upper fs does not support xattr.\n"); } else { vfs_removexattr(ofs->workdir, OVL_XATTR_OPAQUE); } /* Check if upper/work fs supports file handles */ if (ofs->config.index && !ovl_can_decode_fh(ofs->workdir->d_sb)) { ofs->config.index = false; pr_warn("overlayfs: upper fs does not support file handles, falling back to index=off.\n"); } return 0; } static int ovl_get_workdir(struct ovl_fs *ofs, struct path *upperpath) { int err; struct path workpath = { }; err = ovl_mount_dir(ofs->config.workdir, &workpath); if (err) goto out; err = -EINVAL; if (upperpath->mnt != workpath.mnt) { pr_err("overlayfs: workdir and upperdir must reside under the same mount\n"); goto out; } if (!ovl_workdir_ok(workpath.dentry, upperpath->dentry)) { pr_err("overlayfs: workdir and upperdir must be separate subtrees\n"); goto out; } err = -EBUSY; if (ovl_inuse_trylock(workpath.dentry)) { ofs->workdir_locked = true; } else if (ofs->config.index) { pr_err("overlayfs: workdir is in-use by another mount, mount with '-o index=off' to override exclusive workdir protection.\n"); goto out; } else { pr_warn("overlayfs: workdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n"); } ofs->workbasedir = dget(workpath.dentry); err = ovl_make_workdir(ofs, &workpath); if (err) goto out; err = 0; out: path_put(&workpath); return err; } static int ovl_get_indexdir(struct ovl_fs *ofs, struct ovl_entry *oe, struct path *upperpath) { int err; /* Verify lower root is upper root origin */ err = ovl_verify_origin(upperpath->dentry, oe->lowerstack[0].dentry, false, true); if (err) { pr_err("overlayfs: failed to verify upper root origin\n"); goto out; } ofs->indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true); if (ofs->indexdir) { /* Verify upper root is index dir origin */ err = ovl_verify_origin(ofs->indexdir, upperpath->dentry, true, true); if (err) pr_err("overlayfs: failed to verify index dir origin\n"); /* Cleanup bad/stale/orphan index entries */ if (!err) err = ovl_indexdir_cleanup(ofs->indexdir, ofs->upper_mnt, oe->lowerstack, oe->numlower); } if (err || !ofs->indexdir) pr_warn("overlayfs: try deleting index dir or mounting with '-o index=off' to disable inodes index.\n"); out: return err; } static int ovl_get_lower_layers(struct ovl_fs *ofs, struct path *stack, unsigned int numlower) { int err; unsigned int i; err = -ENOMEM; ofs->lower_layers = kcalloc(numlower, sizeof(struct ovl_layer), GFP_KERNEL); if (ofs->lower_layers == NULL) goto out; for (i = 0; i < numlower; i++) { struct vfsmount *mnt; dev_t dev; err = get_anon_bdev(&dev); if (err) { pr_err("overlayfs: failed to get anonymous bdev for lowerpath\n"); goto out; } mnt = clone_private_mount(&stack[i]); err = PTR_ERR(mnt); if (IS_ERR(mnt)) { pr_err("overlayfs: failed to clone lowerpath\n"); free_anon_bdev(dev); goto out; } /* * Make lower layers R/O. That way fchmod/fchown on lower file * will fail instead of modifying lower fs. */ mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME; ofs->lower_layers[ofs->numlower].mnt = mnt; ofs->lower_layers[ofs->numlower].pseudo_dev = dev; ofs->numlower++; /* Check if all lower layers are on same sb */ if (i == 0) ofs->same_sb = mnt->mnt_sb; else if (ofs->same_sb != mnt->mnt_sb) ofs->same_sb = NULL; } err = 0; out: return err; } static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb, struct ovl_fs *ofs) { int err; char *lowertmp, *lower; struct path *stack = NULL; unsigned int stacklen, numlower = 0, i; bool remote = false; struct ovl_entry *oe; err = -ENOMEM; lowertmp = kstrdup(ofs->config.lowerdir, GFP_KERNEL); if (!lowertmp) goto out_err; err = -EINVAL; stacklen = ovl_split_lowerdirs(lowertmp); if (stacklen > OVL_MAX_STACK) { pr_err("overlayfs: too many lower directories, limit is %d\n", OVL_MAX_STACK); goto out_err; } else if (!ofs->config.upperdir && stacklen == 1) { pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n"); goto out_err; } err = -ENOMEM; stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL); if (!stack) goto out_err; err = -EINVAL; lower = lowertmp; for (numlower = 0; numlower < stacklen; numlower++) { err = ovl_lower_dir(lower, &stack[numlower], ofs, &sb->s_stack_depth, &remote); if (err) goto out_err; lower = strchr(lower, '\0') + 1; } err = -EINVAL; sb->s_stack_depth++; if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) { pr_err("overlayfs: maximum fs stacking depth exceeded\n"); goto out_err; } err = ovl_get_lower_layers(ofs, stack, numlower); if (err) goto out_err; err = -ENOMEM; oe = ovl_alloc_entry(numlower); if (!oe) goto out_err; for (i = 0; i < numlower; i++) { oe->lowerstack[i].dentry = dget(stack[i].dentry); oe->lowerstack[i].layer = &ofs->lower_layers[i]; } if (remote) sb->s_d_op = &ovl_reval_dentry_operations; else sb->s_d_op = &ovl_dentry_operations; out: for (i = 0; i < numlower; i++) path_put(&stack[i]); kfree(stack); kfree(lowertmp); return oe; out_err: oe = ERR_PTR(err); goto out; } static int ovl_fill_super(struct super_block *sb, void *data, int silent) { struct path upperpath = { }; struct dentry *root_dentry; struct ovl_entry *oe; struct ovl_fs *ofs; struct cred *cred; int err; err = -ENOMEM; ofs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL); if (!ofs) goto out; ofs->creator_cred = cred = prepare_creds(); if (!cred) goto out_err; ofs->config.redirect_dir = ovl_redirect_dir_def; ofs->config.index = ovl_index_def; err = ovl_parse_opt((char *) data, &ofs->config); if (err) goto out_err; err = -EINVAL; if (!ofs->config.lowerdir) { if (!silent) pr_err("overlayfs: missing 'lowerdir'\n"); goto out_err; } sb->s_stack_depth = 0; sb->s_maxbytes = MAX_LFS_FILESIZE; if (ofs->config.upperdir) { if (!ofs->config.workdir) { pr_err("overlayfs: missing 'workdir'\n"); goto out_err; } err = ovl_get_upper(ofs, &upperpath); if (err) goto out_err; err = ovl_get_workdir(ofs, &upperpath); if (err) goto out_err; if (!ofs->workdir) sb->s_flags |= MS_RDONLY; sb->s_stack_depth = ofs->upper_mnt->mnt_sb->s_stack_depth; sb->s_time_gran = ofs->upper_mnt->mnt_sb->s_time_gran; } oe = ovl_get_lowerstack(sb, ofs); err = PTR_ERR(oe); if (IS_ERR(oe)) goto out_err; /* If the upper fs is nonexistent, we mark overlayfs r/o too */ if (!ofs->upper_mnt) sb->s_flags |= MS_RDONLY; else if (ofs->upper_mnt->mnt_sb != ofs->same_sb) ofs->same_sb = NULL; if (!(ovl_force_readonly(ofs)) && ofs->config.index) { err = ovl_get_indexdir(ofs, oe, &upperpath); if (err) goto out_free_oe; if (!ofs->indexdir) sb->s_flags |= MS_RDONLY; } /* Show index=off/on in /proc/mounts for any of the reasons above */ if (!ofs->indexdir) ofs->config.index = false; /* Never override disk quota limits or use reserved space */ cap_lower(cred->cap_effective, CAP_SYS_RESOURCE); sb->s_magic = OVERLAYFS_SUPER_MAGIC; sb->s_op = &ovl_super_operations; sb->s_xattr = ovl_xattr_handlers; sb->s_fs_info = ofs; sb->s_flags |= MS_POSIXACL | MS_NOREMOTELOCK; err = -ENOMEM; root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, 0)); if (!root_dentry) goto out_free_oe; mntput(upperpath.mnt); if (upperpath.dentry) { oe->has_upper = true; if (ovl_is_impuredir(upperpath.dentry)) ovl_set_flag(OVL_IMPURE, d_inode(root_dentry)); } root_dentry->d_fsdata = oe; /* Root is always merge -> can have whiteouts */ ovl_set_flag(OVL_WHITEOUTS, d_inode(root_dentry)); ovl_inode_init(d_inode(root_dentry), upperpath.dentry, ovl_dentry_lower(root_dentry)); sb->s_root = root_dentry; return 0; out_free_oe: ovl_entry_stack_free(oe); kfree(oe); out_err: path_put(&upperpath); ovl_free_fs(ofs); out: return err; } static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags, const char *dev_name, void *raw_data) { return mount_nodev(fs_type, flags, raw_data, ovl_fill_super); } static struct file_system_type ovl_fs_type = { .owner = THIS_MODULE, .name = "overlay", .mount = ovl_mount, .kill_sb = kill_anon_super, }; MODULE_ALIAS_FS("overlay"); static void ovl_inode_init_once(void *foo) { struct ovl_inode *oi = foo; inode_init_once(&oi->vfs_inode); } static int __init ovl_init(void) { int err; ovl_inode_cachep = kmem_cache_create("ovl_inode", sizeof(struct ovl_inode), 0, (SLAB_RECLAIM_ACCOUNT| SLAB_MEM_SPREAD|SLAB_ACCOUNT), ovl_inode_init_once); if (ovl_inode_cachep == NULL) return -ENOMEM; err = register_filesystem(&ovl_fs_type); if (err) kmem_cache_destroy(ovl_inode_cachep); return err; } static void __exit ovl_exit(void) { unregister_filesystem(&ovl_fs_type); /* * Make sure all delayed rcu free inodes are flushed before we * destroy cache. */ rcu_barrier(); kmem_cache_destroy(ovl_inode_cachep); } module_init(ovl_init); module_exit(ovl_exit);