diff options
Diffstat (limited to 'fs/nfs/getroot.c')
| -rw-r--r-- | fs/nfs/getroot.c | 164 |
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; +} |