diff options
Diffstat (limited to 'fs/overlayfs/util.c')
| -rw-r--r-- | fs/overlayfs/util.c | 945 |
1 files changed, 945 insertions, 0 deletions
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c new file mode 100644 index 000000000..db8bdb29b --- /dev/null +++ b/fs/overlayfs/util.c @@ -0,0 +1,945 @@ +/* + * 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) { + if (ovl_test_flag(OVL_CONST_INO, d_inode(dentry))) + type |= __OVL_PATH_ORIGIN; + if (d_is_dir(dentry) || + !ovl_has_upperdata(d_inode(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) { }; + } +} + +void ovl_path_lowerdata(struct dentry *dentry, struct path *path) +{ + struct ovl_entry *oe = dentry->d_fsdata; + + if (oe->numlower) { + path->mnt = oe->lowerstack[oe->numlower - 1].layer->mnt; + path->dentry = oe->lowerstack[oe->numlower - 1].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; +} + +/* + * ovl_dentry_lower() could return either a data dentry or metacopy dentry + * dependig on what is stored in lowerstack[0]. At times we need to find + * lower dentry which has data (and not metacopy dentry). This helper + * returns the lower data dentry. + */ +struct dentry *ovl_dentry_lowerdata(struct dentry *dentry) +{ + struct ovl_entry *oe = dentry->d_fsdata; + + return oe->numlower ? oe->lowerstack[oe->numlower - 1].dentry : 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); +} + +/* Return inode which contains lower data. Do not return metacopy */ +struct inode *ovl_inode_lowerdata(struct inode *inode) +{ + if (WARN_ON(!S_ISREG(inode->i_mode))) + return NULL; + + return OVL_I(inode)->lowerdata ?: ovl_inode_lower(inode); +} + +/* Return real inode which contains data. Does not return metacopy inode */ +struct inode *ovl_inode_realdata(struct inode *inode) +{ + struct inode *upperinode; + + upperinode = ovl_inode_upper(inode); + if (upperinode && ovl_has_upperdata(inode)) + return upperinode; + + return ovl_inode_lowerdata(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); +} + +static bool ovl_should_check_upperdata(struct inode *inode) +{ + if (!S_ISREG(inode->i_mode)) + return false; + + if (!ovl_inode_lower(inode)) + return false; + + return true; +} + +bool ovl_has_upperdata(struct inode *inode) +{ + if (!ovl_should_check_upperdata(inode)) + return true; + + if (!ovl_test_flag(OVL_UPPERDATA, inode)) + return false; + /* + * Pairs with smp_wmb() in ovl_set_upperdata(). Main user of + * ovl_has_upperdata() is ovl_copy_up_meta_inode_data(). Make sure + * if setting of OVL_UPPERDATA is visible, then effects of writes + * before that are visible too. + */ + smp_rmb(); + return true; +} + +void ovl_set_upperdata(struct inode *inode) +{ + /* + * Pairs with smp_rmb() in ovl_has_upperdata(). Make sure + * if OVL_UPPERDATA flag is visible, then effects of write operations + * before it are visible as well. + */ + smp_wmb(); + ovl_set_flag(OVL_UPPERDATA, inode); +} + +/* Caller should hold ovl_inode->lock */ +bool ovl_dentry_needs_data_copy_up_locked(struct dentry *dentry, int flags) +{ + if (!ovl_open_flags_need_copy_up(flags)) + return false; + + return !ovl_test_flag(OVL_UPPERDATA, d_inode(dentry)); +} + +bool ovl_dentry_needs_data_copy_up(struct dentry *dentry, int flags) +{ + if (!ovl_open_flags_need_copy_up(flags)) + return false; + + return !ovl_has_upperdata(d_inode(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 dentry *lowerdata) +{ + struct inode *realinode = d_inode(upperdentry ?: lowerdentry); + + if (upperdentry) + OVL_I(inode)->__upperdentry = upperdentry; + if (lowerdentry) + OVL_I(inode)->lower = igrab(d_inode(lowerdentry)); + if (lowerdata) + OVL_I(inode)->lowerdata = igrab(d_inode(lowerdata)); + + ovl_copyattr(realinode, inode); + ovl_copyflags(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); + } +} + +static 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++; +} + +void ovl_dir_modified(struct dentry *dentry, bool impurity) +{ + /* Copy mtime/ctime */ + ovl_copyattr(d_inode(ovl_dentry_upper(dentry)), d_inode(dentry)); + + ovl_dentry_version_inc(dentry, impurity); +} + +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()); +} + +/* Caller should hold ovl_inode->lock */ +static bool ovl_already_copied_up_locked(struct dentry *dentry, int flags) +{ + bool disconnected = dentry->d_flags & DCACHE_DISCONNECTED; + + if (ovl_dentry_upper(dentry) && + (ovl_dentry_has_upper_alias(dentry) || disconnected) && + !ovl_dentry_needs_data_copy_up_locked(dentry, flags)) + return true; + + return false; +} + +bool ovl_already_copied_up(struct dentry *dentry, int flags) +{ + bool disconnected = dentry->d_flags & DCACHE_DISCONNECTED; + + /* + * Check if copy-up has happened as well as for upper alias (in + * case of hard links) is there. + * + * Both checks are lockless: + * - false negatives: will recheck under oi->lock + * - false positives: + * + ovl_dentry_upper() uses memory barriers to ensure the + * upper dentry is up-to-date + * + ovl_dentry_has_upper_alias() relies on locking of + * upper parent i_rwsem to prevent reordering copy-up + * with rename. + */ + if (ovl_dentry_upper(dentry) && + (ovl_dentry_has_upper_alias(dentry) || disconnected) && + !ovl_dentry_needs_data_copy_up(dentry, flags)) + return true; + + return false; +} + +int ovl_copy_up_start(struct dentry *dentry, int flags) +{ + struct ovl_inode *oi = OVL_I(d_inode(dentry)); + int err; + + err = mutex_lock_interruptible(&oi->lock); + if (!err && ovl_already_copied_up_locked(dentry, flags)) { + 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); + } +} + +bool ovl_is_inuse(struct dentry *dentry) +{ + struct inode *inode = d_inode(dentry); + bool inuse; + + spin_lock(&inode->i_lock); + inuse = (inode->i_state & I_OVL_INUSE); + spin_unlock(&inode->i_lock); + + return inuse; +} + +/* + * 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: + kfree(name.name); + 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; +} + +/* err < 0, 0 if no metacopy xattr, 1 if metacopy xattr found */ +int ovl_check_metacopy_xattr(struct dentry *dentry) +{ + int res; + + /* Only regular files can have metacopy xattr */ + if (!S_ISREG(d_inode(dentry)->i_mode)) + return 0; + + res = vfs_getxattr(dentry, OVL_XATTR_METACOPY, NULL, 0); + if (res < 0) { + if (res == -ENODATA || res == -EOPNOTSUPP) + return 0; + goto out; + } + + return 1; +out: + pr_warn_ratelimited("overlayfs: failed to get metacopy (%i)\n", res); + return res; +} + +bool ovl_is_metacopy_dentry(struct dentry *dentry) +{ + struct ovl_entry *oe = dentry->d_fsdata; + + if (!d_is_reg(dentry)) + return false; + + if (ovl_dentry_upper(dentry)) { + if (!ovl_has_upperdata(d_inode(dentry))) + return true; + return false; + } + + return (oe->numlower > 1); +} + +ssize_t ovl_getxattr(struct dentry *dentry, char *name, char **value, + size_t padding) +{ + ssize_t res; + char *buf = NULL; + + res = vfs_getxattr(dentry, name, NULL, 0); + if (res < 0) { + if (res == -ENODATA || res == -EOPNOTSUPP) + return -ENODATA; + goto fail; + } + + if (res != 0) { + buf = kzalloc(res + padding, GFP_KERNEL); + if (!buf) + return -ENOMEM; + + res = vfs_getxattr(dentry, name, buf, res); + if (res < 0) + goto fail; + } + *value = buf; + + return res; + +fail: + pr_warn_ratelimited("overlayfs: failed to get xattr %s: err=%zi)\n", + name, res); + kfree(buf); + return res; +} + +char *ovl_get_redirect_xattr(struct dentry *dentry, int padding) +{ + int res; + char *s, *next, *buf = NULL; + + res = ovl_getxattr(dentry, OVL_XATTR_REDIRECT, &buf, padding + 1); + if (res == -ENODATA) + return NULL; + if (res < 0) + return ERR_PTR(res); + if (res == 0) + goto invalid; + + if (buf[0] == '/') { + for (s = buf; *s++ == '/'; s = next) { + next = strchrnul(s, '/'); + if (s == next) + goto invalid; + } + } else { + if (strchr(buf, '/') != NULL) + goto invalid; + } + + return buf; +invalid: + pr_warn_ratelimited("overlayfs: invalid redirect (%s)\n", buf); + res = -EINVAL; + kfree(buf); + return ERR_PTR(res); +} |