// SPDX-License-Identifier: GPL-2.0-or-later /* AFS dynamic root handling * * Copyright (C) 2018 Red Hat, Inc. All Rights Reserved. * Written by David Howells (dhowells@redhat.com) */ #include <linux/fs.h> #include <linux/namei.h> #include <linux/dns_resolver.h> #include "internal.h" static atomic_t afs_autocell_ino; /* * iget5() comparator for inode created by autocell operations * * These pseudo inodes don't match anything. */ static int afs_iget5_pseudo_test(struct inode *inode, void *opaque) { return 0; } /* * iget5() inode initialiser */ static int afs_iget5_pseudo_set(struct inode *inode, void *opaque) { struct afs_super_info *as = AFS_FS_S(inode->i_sb); struct afs_vnode *vnode = AFS_FS_I(inode); struct afs_fid *fid = opaque; vnode->volume = as->volume; vnode->fid = *fid; inode->i_ino = fid->vnode; inode->i_generation = fid->unique; return 0; } /* * Create an inode for a dynamic root directory or an autocell dynamic * automount dir. */ struct inode *afs_iget_pseudo_dir(struct super_block *sb, bool root) { struct afs_super_info *as = AFS_FS_S(sb); struct afs_vnode *vnode; struct inode *inode; struct afs_fid fid = {}; _enter(""); if (as->volume) fid.vid = as->volume->vid; if (root) { fid.vnode = 1; fid.unique = 1; } else { fid.vnode = atomic_inc_return(&afs_autocell_ino); fid.unique = 0; } inode = iget5_locked(sb, fid.vnode, afs_iget5_pseudo_test, afs_iget5_pseudo_set, &fid); if (!inode) { _leave(" = -ENOMEM"); return ERR_PTR(-ENOMEM); } _debug("GOT INODE %p { ino=%lu, vl=%llx, vn=%llx, u=%x }", inode, inode->i_ino, fid.vid, fid.vnode, fid.unique); vnode = AFS_FS_I(inode); /* there shouldn't be an existing inode */ BUG_ON(!(inode->i_state & I_NEW)); netfs_inode_init(&vnode->netfs, NULL); inode->i_size = 0; inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO; if (root) { inode->i_op = &afs_dynroot_inode_operations; inode->i_fop = &simple_dir_operations; } else { inode->i_op = &afs_autocell_inode_operations; } set_nlink(inode, 2); inode->i_uid = GLOBAL_ROOT_UID; inode->i_gid = GLOBAL_ROOT_GID; inode->i_atime = inode->i_mtime = inode_set_ctime_current(inode); inode->i_blocks = 0; inode->i_generation = 0; set_bit(AFS_VNODE_PSEUDODIR, &vnode->flags); if (!root) { set_bit(AFS_VNODE_MOUNTPOINT, &vnode->flags); inode->i_flags |= S_AUTOMOUNT; } inode->i_flags |= S_NOATIME; unlock_new_inode(inode); _leave(" = %p", inode); return inode; } /* * Probe to see if a cell may exist. This prevents positive dentries from * being created unnecessarily. */ static int afs_probe_cell_name(struct dentry *dentry) { struct afs_cell *cell; struct afs_net *net = afs_d2net(dentry); const char *name = dentry->d_name.name; size_t len = dentry->d_name.len; char *result = NULL; int ret; /* Names prefixed with a dot are R/W mounts. */ if (name[0] == '.') { if (len == 1) return -EINVAL; name++; len--; } cell = afs_find_cell(net, name, len, afs_cell_trace_use_probe); if (!IS_ERR(cell)) { afs_unuse_cell(net, cell, afs_cell_trace_unuse_probe); return 0; } ret = dns_query(net->net, "afsdb", name, len, "srv=1", &result, NULL, false); if (ret == -ENODATA || ret == -ENOKEY || ret == 0) ret = -ENOENT; if (ret > 0 && ret >= sizeof(struct dns_server_list_v1_header)) { struct dns_server_list_v1_header *v1 = (void *)result; if (v1->hdr.zero == 0 && v1->hdr.content == DNS_PAYLOAD_IS_SERVER_LIST && v1->hdr.version == 1 && (v1->status != DNS_LOOKUP_GOOD && v1->status != DNS_LOOKUP_GOOD_WITH_BAD)) return -ENOENT; } kfree(result); return ret; } /* * Try to auto mount the mountpoint with pseudo directory, if the autocell * operation is setted. */ struct inode *afs_try_auto_mntpt(struct dentry *dentry, struct inode *dir) { struct afs_vnode *vnode = AFS_FS_I(dir); struct inode *inode; int ret = -ENOENT; _enter("%p{%pd}, {%llx:%llu}", dentry, dentry, vnode->fid.vid, vnode->fid.vnode); if (!test_bit(AFS_VNODE_AUTOCELL, &vnode->flags)) goto out; ret = afs_probe_cell_name(dentry); if (ret < 0) goto out; inode = afs_iget_pseudo_dir(dir->i_sb, false); if (IS_ERR(inode)) { ret = PTR_ERR(inode); goto out; } _leave("= %p", inode); return inode; out: _leave("= %d", ret); return ret == -ENOENT ? NULL : ERR_PTR(ret); } /* * Look up @cell in a dynroot directory. This is a substitution for the * local cell name for the net namespace. */ static struct dentry *afs_lookup_atcell(struct dentry *dentry) { struct afs_cell *cell; struct afs_net *net = afs_d2net(dentry); struct dentry *ret; char *name; int len; if (!net->ws_cell) return ERR_PTR(-ENOENT); ret = ERR_PTR(-ENOMEM); name = kmalloc(AFS_MAXCELLNAME + 1, GFP_KERNEL); if (!name) goto out_p; down_read(&net->cells_lock); cell = net->ws_cell; if (cell) { len = cell->name_len; memcpy(name, cell->name, len + 1); } up_read(&net->cells_lock); ret = ERR_PTR(-ENOENT); if (!cell) goto out_n; ret = lookup_one_len(name, dentry->d_parent, len); /* We don't want to d_add() the @cell dentry here as we don't want to * the cached dentry to hide changes to the local cell name. */ out_n: kfree(name); out_p: return ret; } /* * Look up an entry in a dynroot directory. */ static struct dentry *afs_dynroot_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags) { _enter("%pd", dentry); ASSERTCMP(d_inode(dentry), ==, NULL); if (flags & LOOKUP_CREATE) return ERR_PTR(-EOPNOTSUPP); if (dentry->d_name.len >= AFSNAMEMAX) { _leave(" = -ENAMETOOLONG"); return ERR_PTR(-ENAMETOOLONG); } if (dentry->d_name.len == 5 && memcmp(dentry->d_name.name, "@cell", 5) == 0) return afs_lookup_atcell(dentry); return d_splice_alias(afs_try_auto_mntpt(dentry, dir), dentry); } const struct inode_operations afs_dynroot_inode_operations = { .lookup = afs_dynroot_lookup, }; /* * Dirs in the dynamic root don't need revalidation. */ static int afs_dynroot_d_revalidate(struct dentry *dentry, unsigned int flags) { return 1; } const struct dentry_operations afs_dynroot_dentry_operations = { .d_revalidate = afs_dynroot_d_revalidate, .d_delete = always_delete_dentry, .d_release = afs_d_release, .d_automount = afs_d_automount, }; /* * Create a manually added cell mount directory. * - The caller must hold net->proc_cells_lock */ int afs_dynroot_mkdir(struct afs_net *net, struct afs_cell *cell) { struct super_block *sb = net->dynroot_sb; struct dentry *root, *subdir; int ret; if (!sb || atomic_read(&sb->s_active) == 0) return 0; /* Let the ->lookup op do the creation */ root = sb->s_root; inode_lock(root->d_inode); subdir = lookup_one_len(cell->name, root, cell->name_len); if (IS_ERR(subdir)) { ret = PTR_ERR(subdir); goto unlock; } /* Note that we're retaining an extra ref on the dentry */ subdir->d_fsdata = (void *)1UL; ret = 0; unlock: inode_unlock(root->d_inode); return ret; } /* * Remove a manually added cell mount directory. * - The caller must hold net->proc_cells_lock */ void afs_dynroot_rmdir(struct afs_net *net, struct afs_cell *cell) { struct super_block *sb = net->dynroot_sb; struct dentry *root, *subdir; if (!sb || atomic_read(&sb->s_active) == 0) return; root = sb->s_root; inode_lock(root->d_inode); /* Don't want to trigger a lookup call, which will re-add the cell */ subdir = try_lookup_one_len(cell->name, root, cell->name_len); if (IS_ERR_OR_NULL(subdir)) { _debug("lookup %ld", PTR_ERR(subdir)); goto no_dentry; } _debug("rmdir %pd %u", subdir, d_count(subdir)); if (subdir->d_fsdata) { _debug("unpin %u", d_count(subdir)); subdir->d_fsdata = NULL; dput(subdir); } dput(subdir); no_dentry: inode_unlock(root->d_inode); _leave(""); } /* * Populate a newly created dynamic root with cell names. */ int afs_dynroot_populate(struct super_block *sb) { struct afs_cell *cell; struct afs_net *net = afs_sb2net(sb); int ret; mutex_lock(&net->proc_cells_lock); net->dynroot_sb = sb; hlist_for_each_entry(cell, &net->proc_cells, proc_link) { ret = afs_dynroot_mkdir(net, cell); if (ret < 0) goto error; } ret = 0; out: mutex_unlock(&net->proc_cells_lock); return ret; error: net->dynroot_sb = NULL; goto out; } /* * When a dynamic root that's in the process of being destroyed, depopulate it * of pinned directories. */ void afs_dynroot_depopulate(struct super_block *sb) { struct afs_net *net = afs_sb2net(sb); struct dentry *root = sb->s_root, *subdir, *tmp; /* Prevent more subdirs from being created */ mutex_lock(&net->proc_cells_lock); if (net->dynroot_sb == sb) net->dynroot_sb = NULL; mutex_unlock(&net->proc_cells_lock); if (root) { inode_lock(root->d_inode); /* Remove all the pins for dirs created for manually added cells */ list_for_each_entry_safe(subdir, tmp, &root->d_subdirs, d_child) { if (subdir->d_fsdata) { subdir->d_fsdata = NULL; dput(subdir); } } inode_unlock(root->d_inode); } }