1 files changed, 397 insertions, 0 deletions
diff --git a/fs/afs/dynroot.c b/fs/afs/dynroot.c
new file mode 100644
index 0000000000..10905a53d5
--- /dev/null
+++ b/fs/afs/dynroot.c
@@ -0,0 +1,397 @@
+// 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);
+	}
+}