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-rw-r--r--fs/nfs/getroot.c164
1 files changed, 164 insertions, 0 deletions
diff --git a/fs/nfs/getroot.c b/fs/nfs/getroot.c
new file mode 100644
index 000000000..11ff2b2e0
--- /dev/null
+++ b/fs/nfs/getroot.c
@@ -0,0 +1,164 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* getroot.c: get the root dentry for an NFS mount
+ *
+ * Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+
+#include <linux/time.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/string.h>
+#include <linux/stat.h>
+#include <linux/errno.h>
+#include <linux/unistd.h>
+#include <linux/sunrpc/clnt.h>
+#include <linux/sunrpc/stats.h>
+#include <linux/nfs_fs.h>
+#include <linux/nfs_mount.h>
+#include <linux/lockd/bind.h>
+#include <linux/seq_file.h>
+#include <linux/mount.h>
+#include <linux/vfs.h>
+#include <linux/namei.h>
+#include <linux/security.h>
+
+#include <linux/uaccess.h>
+
+#include "internal.h"
+
+#define NFSDBG_FACILITY NFSDBG_CLIENT
+
+/*
+ * Set the superblock root dentry.
+ * Note that this function frees the inode in case of error.
+ */
+static int nfs_superblock_set_dummy_root(struct super_block *sb, struct inode *inode)
+{
+ /* The mntroot acts as the dummy root dentry for this superblock */
+ if (sb->s_root == NULL) {
+ sb->s_root = d_make_root(inode);
+ if (sb->s_root == NULL)
+ return -ENOMEM;
+ ihold(inode);
+ /*
+ * Ensure that this dentry is invisible to d_find_alias().
+ * Otherwise, it may be spliced into the tree by
+ * d_splice_alias if a parent directory from the same
+ * filesystem gets mounted at a later time.
+ * This again causes shrink_dcache_for_umount_subtree() to
+ * Oops, since the test for IS_ROOT() will fail.
+ */
+ spin_lock(&d_inode(sb->s_root)->i_lock);
+ spin_lock(&sb->s_root->d_lock);
+ hlist_del_init(&sb->s_root->d_u.d_alias);
+ spin_unlock(&sb->s_root->d_lock);
+ spin_unlock(&d_inode(sb->s_root)->i_lock);
+ }
+ return 0;
+}
+
+/*
+ * get an NFS2/NFS3 root dentry from the root filehandle
+ */
+int nfs_get_root(struct super_block *s, struct fs_context *fc)
+{
+ struct nfs_fs_context *ctx = nfs_fc2context(fc);
+ struct nfs_server *server = NFS_SB(s), *clone_server;
+ struct nfs_fsinfo fsinfo;
+ struct dentry *root;
+ struct inode *inode;
+ char *name;
+ int error = -ENOMEM;
+ unsigned long kflags = 0, kflags_out = 0;
+
+ name = kstrdup(fc->source, GFP_KERNEL);
+ if (!name)
+ goto out;
+
+ /* get the actual root for this mount */
+ fsinfo.fattr = nfs_alloc_fattr_with_label(server);
+ if (fsinfo.fattr == NULL)
+ goto out_name;
+
+ error = server->nfs_client->rpc_ops->getroot(server, ctx->mntfh, &fsinfo);
+ if (error < 0) {
+ dprintk("nfs_get_root: getattr error = %d\n", -error);
+ nfs_errorf(fc, "NFS: Couldn't getattr on root");
+ goto out_fattr;
+ }
+
+ inode = nfs_fhget(s, ctx->mntfh, fsinfo.fattr);
+ if (IS_ERR(inode)) {
+ dprintk("nfs_get_root: get root inode failed\n");
+ error = PTR_ERR(inode);
+ nfs_errorf(fc, "NFS: Couldn't get root inode");
+ goto out_fattr;
+ }
+
+ error = nfs_superblock_set_dummy_root(s, inode);
+ if (error != 0)
+ goto out_fattr;
+
+ /* root dentries normally start off anonymous and get spliced in later
+ * if the dentry tree reaches them; however if the dentry already
+ * exists, we'll pick it up at this point and use it as the root
+ */
+ root = d_obtain_root(inode);
+ if (IS_ERR(root)) {
+ dprintk("nfs_get_root: get root dentry failed\n");
+ error = PTR_ERR(root);
+ nfs_errorf(fc, "NFS: Couldn't get root dentry");
+ goto out_fattr;
+ }
+
+ security_d_instantiate(root, inode);
+ spin_lock(&root->d_lock);
+ if (IS_ROOT(root) && !root->d_fsdata &&
+ !(root->d_flags & DCACHE_NFSFS_RENAMED)) {
+ root->d_fsdata = name;
+ name = NULL;
+ }
+ spin_unlock(&root->d_lock);
+ fc->root = root;
+ if (server->caps & NFS_CAP_SECURITY_LABEL)
+ kflags |= SECURITY_LSM_NATIVE_LABELS;
+ if (ctx->clone_data.sb) {
+ if (d_inode(fc->root)->i_fop != &nfs_dir_operations) {
+ error = -ESTALE;
+ goto error_splat_root;
+ }
+ /* clone lsm security options from the parent to the new sb */
+ error = security_sb_clone_mnt_opts(ctx->clone_data.sb,
+ s, kflags, &kflags_out);
+ if (error)
+ goto error_splat_root;
+ clone_server = NFS_SB(ctx->clone_data.sb);
+ server->has_sec_mnt_opts = clone_server->has_sec_mnt_opts;
+ } else {
+ error = security_sb_set_mnt_opts(s, fc->security,
+ kflags, &kflags_out);
+ }
+ if (error)
+ goto error_splat_root;
+ if (server->caps & NFS_CAP_SECURITY_LABEL &&
+ !(kflags_out & SECURITY_LSM_NATIVE_LABELS))
+ server->caps &= ~NFS_CAP_SECURITY_LABEL;
+
+ nfs_setsecurity(inode, fsinfo.fattr);
+ error = 0;
+
+out_fattr:
+ nfs_free_fattr(fsinfo.fattr);
+out_name:
+ kfree(name);
+out:
+ return error;
+error_splat_root:
+ dput(fc->root);
+ fc->root = NULL;
+ goto out_fattr;
+}