namei: prepare for idmapped mounts

The various vfs_*() helpers are called by filesystems or by the vfs
itself to perform core operations such as create, link, mkdir, mknod, rename,
rmdir, tmpfile and unlink. Enable them to handle idmapped mounts. If the
inode is accessed through an idmapped mount map it into the
mount's user namespace and pass it down. Afterwards the checks and
operations are identical to non-idmapped mounts. If the initial user
namespace is passed nothing changes so non-idmapped mounts will see
identical behavior as before.

Link: https://lore.kernel.org/r/20210121131959.646623-15-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

2 files changed, 14 insertions, 11 deletions

diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c
index 186fa2c2c6ba..891395c6c7d3 100644
--- a/fs/nfsd/nfs4recover.c
+++ b/fs/nfsd/nfs4recover.c
@@ -233,7 +233,7 @@ nfsd4_create_clid_dir(struct nfs4_client *clp)
 		 * as well be forgiving and just succeed silently.
 		 */
 		goto out_put;
-	status = vfs_mkdir(d_inode(dir), dentry, S_IRWXU);
+	status = vfs_mkdir(&init_user_ns, d_inode(dir), dentry, S_IRWXU);
 out_put:
 	dput(dentry);
 out_unlock:
@@ -353,7 +353,7 @@ nfsd4_unlink_clid_dir(char *name, int namlen, struct nfsd_net *nn)
 	status = -ENOENT;
 	if (d_really_is_negative(dentry))
 		goto out;
-	status = vfs_rmdir(d_inode(dir), dentry);
+	status = vfs_rmdir(&init_user_ns, d_inode(dir), dentry);
 out:
 	dput(dentry);
 out_unlock:
@@ -443,7 +443,7 @@ purge_old(struct dentry *parent, struct dentry *child, struct nfsd_net *nn)
 	if (nfs4_has_reclaimed_state(name, nn))
 		goto out_free;
 
-	status = vfs_rmdir(d_inode(parent), child);
+	status = vfs_rmdir(&init_user_ns, d_inode(parent), child);
 	if (status)
 		printk("failed to remove client recovery directory %pd\n",
 				child);
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index f7d83ff2b44e..fab873178140 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1255,12 +1255,12 @@ nfsd_create_locked(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	host_err = 0;
 	switch (type) {
 	case S_IFREG:
-		host_err = vfs_create(dirp, dchild, iap->ia_mode, true);
+		host_err = vfs_create(&init_user_ns, dirp, dchild, iap->ia_mode, true);
 		if (!host_err)
 			nfsd_check_ignore_resizing(iap);
 		break;
 	case S_IFDIR:
-		host_err = vfs_mkdir(dirp, dchild, iap->ia_mode);
+		host_err = vfs_mkdir(&init_user_ns, dirp, dchild, iap->ia_mode);
 		if (!host_err && unlikely(d_unhashed(dchild))) {
 			struct dentry *d;
 			d = lookup_one_len(dchild->d_name.name,
@@ -1288,7 +1288,8 @@ nfsd_create_locked(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	case S_IFBLK:
 	case S_IFIFO:
 	case S_IFSOCK:
-		host_err = vfs_mknod(dirp, dchild, iap->ia_mode, rdev);
+		host_err = vfs_mknod(&init_user_ns, dirp, dchild,
+				     iap->ia_mode, rdev);
 		break;
 	default:
 		printk(KERN_WARNING "nfsd: bad file type %o in nfsd_create\n",
@@ -1486,7 +1487,7 @@ do_nfsd_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	if (!IS_POSIXACL(dirp))
 		iap->ia_mode &= ~current_umask();
 
-	host_err = vfs_create(dirp, dchild, iap->ia_mode, true);
+	host_err = vfs_create(&init_user_ns, dirp, dchild, iap->ia_mode, true);
 	if (host_err < 0) {
 		fh_drop_write(fhp);
 		goto out_nfserr;
@@ -1610,7 +1611,7 @@ nfsd_symlink(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	if (IS_ERR(dnew))
 		goto out_nfserr;
 
-	host_err = vfs_symlink(d_inode(dentry), dnew, path);
+	host_err = vfs_symlink(&init_user_ns, d_inode(dentry), dnew, path);
 	err = nfserrno(host_err);
 	if (!err)
 		err = nfserrno(commit_metadata(fhp));
@@ -1678,7 +1679,7 @@ nfsd_link(struct svc_rqst *rqstp, struct svc_fh *ffhp,
 	err = nfserr_noent;
 	if (d_really_is_negative(dold))
 		goto out_dput;
-	host_err = vfs_link(dold, dirp, dnew, NULL);
+	host_err = vfs_link(dold, &init_user_ns, dirp, dnew, NULL);
 	if (!host_err) {
 		err = nfserrno(commit_metadata(ffhp));
 		if (!err)
@@ -1799,8 +1800,10 @@ retry:
 		goto out_dput_old;
 	} else {
 		struct renamedata rd = {
+			.old_mnt_userns	= &init_user_ns,
 			.old_dir	= fdir,
 			.old_dentry	= odentry,
+			.new_mnt_userns	= &init_user_ns,
 			.new_dir	= tdir,
 			.new_dentry	= ndentry,
 		};
@@ -1891,9 +1894,9 @@ nfsd_unlink(struct svc_rqst *rqstp, struct svc_fh *fhp, int type,
 	if (type != S_IFDIR) {
 		if (rdentry->d_sb->s_export_op->flags & EXPORT_OP_CLOSE_BEFORE_UNLINK)
 			nfsd_close_cached_files(rdentry);
-		host_err = vfs_unlink(dirp, rdentry, NULL);
+		host_err = vfs_unlink(&init_user_ns, dirp, rdentry, NULL);
 	} else {
-		host_err = vfs_rmdir(dirp, rdentry);
+		host_err = vfs_rmdir(&init_user_ns, dirp, rdentry);
 	}
 
 	if (!host_err)