/* * Copyright (C) 2011 Novell Inc. * Copyright (C) 2016 Red Hat, 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/mount.h> #include <linux/slab.h> #include <linux/cred.h> #include <linux/xattr.h> #include <linux/exportfs.h> #include <linux/uuid.h> #include <linux/namei.h> #include <linux/ratelimit.h> #include "overlayfs.h" int ovl_want_write(struct dentry *dentry) { struct ovl_fs *ofs = dentry->d_sb->s_fs_info; return mnt_want_write(ofs->upper_mnt); } void ovl_drop_write(struct dentry *dentry) { struct ovl_fs *ofs = dentry->d_sb->s_fs_info; mnt_drop_write(ofs->upper_mnt); } struct dentry *ovl_workdir(struct dentry *dentry) { struct ovl_fs *ofs = dentry->d_sb->s_fs_info; return ofs->workdir; } const struct cred *ovl_override_creds(struct super_block *sb) { struct ovl_fs *ofs = sb->s_fs_info; return override_creds(ofs->creator_cred); } struct super_block *ovl_same_sb(struct super_block *sb) { struct ovl_fs *ofs = sb->s_fs_info; if (!ofs->numlowerfs) return ofs->upper_mnt->mnt_sb; else if (ofs->numlowerfs == 1 && !ofs->upper_mnt) return ofs->lower_fs[0].sb; else return NULL; } /* * Check if underlying fs supports file handles and try to determine encoding * type, in order to deduce maximum inode number used by fs. * * Return 0 if file handles are not supported. * Return 1 (FILEID_INO32_GEN) if fs uses the default 32bit inode encoding. * Return -1 if fs uses a non default encoding with unknown inode size. */ int ovl_can_decode_fh(struct super_block *sb) { if (!sb->s_export_op || !sb->s_export_op->fh_to_dentry || uuid_is_null(&sb->s_uuid)) return 0; return sb->s_export_op->encode_fh ? -1 : FILEID_INO32_GEN; } struct dentry *ovl_indexdir(struct super_block *sb) { struct ovl_fs *ofs = sb->s_fs_info; return ofs->indexdir; } /* Index all files on copy up. For now only enabled for NFS export */ bool ovl_index_all(struct super_block *sb) { struct ovl_fs *ofs = sb->s_fs_info; return ofs->config.nfs_export && ofs->config.index; } /* Verify lower origin on lookup. For now only enabled for NFS export */ bool ovl_verify_lower(struct super_block *sb) { struct ovl_fs *ofs = sb->s_fs_info; return ofs->config.nfs_export && ofs->config.index; } struct ovl_entry *ovl_alloc_entry(unsigned int numlower) { size_t size = offsetof(struct ovl_entry, lowerstack[numlower]); struct ovl_entry *oe = kzalloc(size, GFP_KERNEL); if (oe) oe->numlower = numlower; return oe; } bool ovl_dentry_remote(struct dentry *dentry) { return dentry->d_flags & (DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE | DCACHE_OP_REAL); } bool ovl_dentry_weird(struct dentry *dentry) { return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT | DCACHE_MANAGE_TRANSIT | DCACHE_OP_HASH | DCACHE_OP_COMPARE); } enum ovl_path_type ovl_path_type(struct dentry *dentry) { struct ovl_entry *oe = dentry->d_fsdata; enum ovl_path_type type = 0; if (ovl_dentry_upper(dentry)) { type = __OVL_PATH_UPPER; /* * Non-dir dentry can hold lower dentry of its copy up origin. */ if (oe->numlower) { type |= __OVL_PATH_ORIGIN; if (d_is_dir(dentry)) type |= __OVL_PATH_MERGE; } } else { if (oe->numlower > 1) type |= __OVL_PATH_MERGE; } return type; } void ovl_path_upper(struct dentry *dentry, struct path *path) { struct ovl_fs *ofs = dentry->d_sb->s_fs_info; path->mnt = ofs->upper_mnt; path->dentry = ovl_dentry_upper(dentry); } void ovl_path_lower(struct dentry *dentry, struct path *path) { struct ovl_entry *oe = dentry->d_fsdata; if (oe->numlower) { path->mnt = oe->lowerstack[0].layer->mnt; path->dentry = oe->lowerstack[0].dentry; } else { *path = (struct path) { }; } } enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path) { enum ovl_path_type type = ovl_path_type(dentry); if (!OVL_TYPE_UPPER(type)) ovl_path_lower(dentry, path); else ovl_path_upper(dentry, path); return type; } struct dentry *ovl_dentry_upper(struct dentry *dentry) { return ovl_upperdentry_dereference(OVL_I(d_inode(dentry))); } struct dentry *ovl_dentry_lower(struct dentry *dentry) { struct ovl_entry *oe = dentry->d_fsdata; return oe->numlower ? oe->lowerstack[0].dentry : NULL; } struct ovl_layer *ovl_layer_lower(struct dentry *dentry) { struct ovl_entry *oe = dentry->d_fsdata; return oe->numlower ? oe->lowerstack[0].layer : NULL; } struct dentry *ovl_dentry_real(struct dentry *dentry) { return ovl_dentry_upper(dentry) ?: ovl_dentry_lower(dentry); } struct dentry *ovl_i_dentry_upper(struct inode *inode) { return ovl_upperdentry_dereference(OVL_I(inode)); } struct inode *ovl_inode_upper(struct inode *inode) { struct dentry *upperdentry = ovl_i_dentry_upper(inode); return upperdentry ? d_inode(upperdentry) : NULL; } struct inode *ovl_inode_lower(struct inode *inode) { return OVL_I(inode)->lower; } struct inode *ovl_inode_real(struct inode *inode) { return ovl_inode_upper(inode) ?: ovl_inode_lower(inode); } struct ovl_dir_cache *ovl_dir_cache(struct inode *inode) { return OVL_I(inode)->cache; } void ovl_set_dir_cache(struct inode *inode, struct ovl_dir_cache *cache) { OVL_I(inode)->cache = cache; } void ovl_dentry_set_flag(unsigned long flag, struct dentry *dentry) { set_bit(flag, &OVL_E(dentry)->flags); } void ovl_dentry_clear_flag(unsigned long flag, struct dentry *dentry) { clear_bit(flag, &OVL_E(dentry)->flags); } bool ovl_dentry_test_flag(unsigned long flag, struct dentry *dentry) { return test_bit(flag, &OVL_E(dentry)->flags); } bool ovl_dentry_is_opaque(struct dentry *dentry) { return ovl_dentry_test_flag(OVL_E_OPAQUE, dentry); } bool ovl_dentry_is_whiteout(struct dentry *dentry) { return !dentry->d_inode && ovl_dentry_is_opaque(dentry); } void ovl_dentry_set_opaque(struct dentry *dentry) { ovl_dentry_set_flag(OVL_E_OPAQUE, dentry); } /* * For hard links and decoded file handles, it's possible for ovl_dentry_upper() * to return positive, while there's no actual upper alias for the inode. * Copy up code needs to know about the existence of the upper alias, so it * can't use ovl_dentry_upper(). */ bool ovl_dentry_has_upper_alias(struct dentry *dentry) { return ovl_dentry_test_flag(OVL_E_UPPER_ALIAS, dentry); } void ovl_dentry_set_upper_alias(struct dentry *dentry) { ovl_dentry_set_flag(OVL_E_UPPER_ALIAS, dentry); } bool ovl_redirect_dir(struct super_block *sb) { struct ovl_fs *ofs = sb->s_fs_info; return ofs->config.redirect_dir && !ofs->noxattr; } const char *ovl_dentry_get_redirect(struct dentry *dentry) { return OVL_I(d_inode(dentry))->redirect; } void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect) { struct ovl_inode *oi = OVL_I(d_inode(dentry)); kfree(oi->redirect); oi->redirect = redirect; } void ovl_inode_init(struct inode *inode, struct dentry *upperdentry, struct dentry *lowerdentry) { struct inode *realinode = d_inode(upperdentry ?: lowerdentry); if (upperdentry) OVL_I(inode)->__upperdentry = upperdentry; if (lowerdentry) OVL_I(inode)->lower = igrab(d_inode(lowerdentry)); ovl_copyattr(realinode, inode); if (!inode->i_ino) inode->i_ino = realinode->i_ino; } void ovl_inode_update(struct inode *inode, struct dentry *upperdentry) { struct inode *upperinode = d_inode(upperdentry); WARN_ON(OVL_I(inode)->__upperdentry); /* * Make sure upperdentry is consistent before making it visible */ smp_wmb(); OVL_I(inode)->__upperdentry = upperdentry; if (inode_unhashed(inode)) { if (!inode->i_ino) inode->i_ino = upperinode->i_ino; inode->i_private = upperinode; __insert_inode_hash(inode, (unsigned long) upperinode); } } void ovl_dentry_version_inc(struct dentry *dentry, bool impurity) { struct inode *inode = d_inode(dentry); WARN_ON(!inode_is_locked(inode)); /* * Version is used by readdir code to keep cache consistent. For merge * dirs all changes need to be noted. For non-merge dirs, cache only * contains impure (ones which have been copied up and have origins) * entries, so only need to note changes to impure entries. */ if (OVL_TYPE_MERGE(ovl_path_type(dentry)) || impurity) OVL_I(inode)->version++; } u64 ovl_dentry_version_get(struct dentry *dentry) { struct inode *inode = d_inode(dentry); WARN_ON(!inode_is_locked(inode)); return OVL_I(inode)->version; } bool ovl_is_whiteout(struct dentry *dentry) { struct inode *inode = dentry->d_inode; return inode && IS_WHITEOUT(inode); } struct file *ovl_path_open(struct path *path, int flags) { return dentry_open(path, flags | O_NOATIME, current_cred()); } int ovl_copy_up_start(struct dentry *dentry) { struct ovl_inode *oi = OVL_I(d_inode(dentry)); int err; err = mutex_lock_interruptible(&oi->lock); if (!err && ovl_dentry_has_upper_alias(dentry)) { err = 1; /* Already copied up */ mutex_unlock(&oi->lock); } return err; } void ovl_copy_up_end(struct dentry *dentry) { mutex_unlock(&OVL_I(d_inode(dentry))->lock); } bool ovl_check_origin_xattr(struct dentry *dentry) { int res; res = vfs_getxattr(dentry, OVL_XATTR_ORIGIN, NULL, 0); /* Zero size value means "copied up but origin unknown" */ if (res >= 0) return true; return false; } bool ovl_check_dir_xattr(struct dentry *dentry, const char *name) { int res; char val; if (!d_is_dir(dentry)) return false; res = vfs_getxattr(dentry, name, &val, 1); if (res == 1 && val == 'y') return true; return false; } int ovl_check_setxattr(struct dentry *dentry, struct dentry *upperdentry, const char *name, const void *value, size_t size, int xerr) { int err; struct ovl_fs *ofs = dentry->d_sb->s_fs_info; if (ofs->noxattr) return xerr; err = ovl_do_setxattr(upperdentry, name, value, size, 0); if (err == -EOPNOTSUPP) { pr_warn("overlayfs: cannot set %s xattr on upper\n", name); ofs->noxattr = true; return xerr; } return err; } int ovl_set_impure(struct dentry *dentry, struct dentry *upperdentry) { int err; if (ovl_test_flag(OVL_IMPURE, d_inode(dentry))) return 0; /* * Do not fail when upper doesn't support xattrs. * Upper inodes won't have origin nor redirect xattr anyway. */ err = ovl_check_setxattr(dentry, upperdentry, OVL_XATTR_IMPURE, "y", 1, 0); if (!err) ovl_set_flag(OVL_IMPURE, d_inode(dentry)); return err; } void ovl_set_flag(unsigned long flag, struct inode *inode) { set_bit(flag, &OVL_I(inode)->flags); } void ovl_clear_flag(unsigned long flag, struct inode *inode) { clear_bit(flag, &OVL_I(inode)->flags); } bool ovl_test_flag(unsigned long flag, struct inode *inode) { return test_bit(flag, &OVL_I(inode)->flags); } /** * Caller must hold a reference to inode to prevent it from being freed while * it is marked inuse. */ bool ovl_inuse_trylock(struct dentry *dentry) { struct inode *inode = d_inode(dentry); bool locked = false; spin_lock(&inode->i_lock); if (!(inode->i_state & I_OVL_INUSE)) { inode->i_state |= I_OVL_INUSE; locked = true; } spin_unlock(&inode->i_lock); return locked; } void ovl_inuse_unlock(struct dentry *dentry) { if (dentry) { struct inode *inode = d_inode(dentry); spin_lock(&inode->i_lock); WARN_ON(!(inode->i_state & I_OVL_INUSE)); inode->i_state &= ~I_OVL_INUSE; spin_unlock(&inode->i_lock); } } /* * Does this overlay dentry need to be indexed on copy up? */ bool ovl_need_index(struct dentry *dentry) { struct dentry *lower = ovl_dentry_lower(dentry); if (!lower || !ovl_indexdir(dentry->d_sb)) return false; /* Index all files for NFS export and consistency verification */ if (ovl_index_all(dentry->d_sb)) return true; /* Index only lower hardlinks on copy up */ if (!d_is_dir(lower) && d_inode(lower)->i_nlink > 1) return true; return false; } /* Caller must hold OVL_I(inode)->lock */ static void ovl_cleanup_index(struct dentry *dentry) { struct dentry *indexdir = ovl_indexdir(dentry->d_sb); struct inode *dir = indexdir->d_inode; struct dentry *lowerdentry = ovl_dentry_lower(dentry); struct dentry *upperdentry = ovl_dentry_upper(dentry); struct dentry *index = NULL; struct inode *inode; struct qstr name; int err; err = ovl_get_index_name(lowerdentry, &name); if (err) goto fail; inode = d_inode(upperdentry); if (!S_ISDIR(inode->i_mode) && inode->i_nlink != 1) { pr_warn_ratelimited("overlayfs: cleanup linked index (%pd2, ino=%lu, nlink=%u)\n", upperdentry, inode->i_ino, inode->i_nlink); /* * We either have a bug with persistent union nlink or a lower * hardlink was added while overlay is mounted. Adding a lower * hardlink and then unlinking all overlay hardlinks would drop * overlay nlink to zero before all upper inodes are unlinked. * As a safety measure, when that situation is detected, set * the overlay nlink to the index inode nlink minus one for the * index entry itself. */ set_nlink(d_inode(dentry), inode->i_nlink - 1); ovl_set_nlink_upper(dentry); goto out; } inode_lock_nested(dir, I_MUTEX_PARENT); index = lookup_one_len(name.name, indexdir, name.len); err = PTR_ERR(index); if (IS_ERR(index)) { index = NULL; } else if (ovl_index_all(dentry->d_sb)) { /* Whiteout orphan index to block future open by handle */ err = ovl_cleanup_and_whiteout(indexdir, dir, index); } else { /* Cleanup orphan index entries */ err = ovl_cleanup(dir, index); } inode_unlock(dir); if (err) goto fail; out: dput(index); return; fail: pr_err("overlayfs: cleanup index of '%pd2' failed (%i)\n", dentry, err); goto out; } /* * Operations that change overlay inode and upper inode nlink need to be * synchronized with copy up for persistent nlink accounting. */ int ovl_nlink_start(struct dentry *dentry, bool *locked) { struct ovl_inode *oi = OVL_I(d_inode(dentry)); const struct cred *old_cred; int err; if (!d_inode(dentry)) return 0; /* * With inodes index is enabled, we store the union overlay nlink * in an xattr on the index inode. When whiting out an indexed lower, * we need to decrement the overlay persistent nlink, but before the * first copy up, we have no upper index inode to store the xattr. * * As a workaround, before whiteout/rename over an indexed lower, * copy up to create the upper index. Creating the upper index will * initialize the overlay nlink, so it could be dropped if unlink * or rename succeeds. * * TODO: implement metadata only index copy up when called with * ovl_copy_up_flags(dentry, O_PATH). */ if (ovl_need_index(dentry) && !ovl_dentry_has_upper_alias(dentry)) { err = ovl_copy_up(dentry); if (err) return err; } err = mutex_lock_interruptible(&oi->lock); if (err) return err; if (d_is_dir(dentry) || !ovl_test_flag(OVL_INDEX, d_inode(dentry))) goto out; old_cred = ovl_override_creds(dentry->d_sb); /* * The overlay inode nlink should be incremented/decremented IFF the * upper operation succeeds, along with nlink change of upper inode. * Therefore, before link/unlink/rename, we store the union nlink * value relative to the upper inode nlink in an upper inode xattr. */ err = ovl_set_nlink_upper(dentry); revert_creds(old_cred); out: if (err) mutex_unlock(&oi->lock); else *locked = true; return err; } void ovl_nlink_end(struct dentry *dentry, bool locked) { if (locked) { if (ovl_test_flag(OVL_INDEX, d_inode(dentry)) && d_inode(dentry)->i_nlink == 0) { const struct cred *old_cred; old_cred = ovl_override_creds(dentry->d_sb); ovl_cleanup_index(dentry); revert_creds(old_cred); } mutex_unlock(&OVL_I(d_inode(dentry))->lock); } } int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *upperdir) { /* Workdir should not be the same as upperdir */ if (workdir == upperdir) goto err; /* Workdir should not be subdir of upperdir and vice versa */ if (lock_rename(workdir, upperdir) != NULL) goto err_unlock; return 0; err_unlock: unlock_rename(workdir, upperdir); err: pr_err("overlayfs: failed to lock workdir+upperdir\n"); return -EIO; }