NFSD: Return NFS4ERR_FILE_OPEN only when linking an open file

RFC 8881 Section 18.9.4 paragraphs 1 - 2 tell us that RENAME should
return NFS4ERR_FILE_OPEN only when the target object is a file that
is currently open. If the target is a directory, some other status
must be returned.

The VFS is unlikely to return -EBUSY, but NFSD has to ensure that
errno does not leak to clients as a status code that is not
permitted by spec.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index adf092406d79e102e1f0d31d90f4a6aed1f5d4ff..4021b047eb1804f0058f6fb511d3fdfc03a42bf3 100644 (file)
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1698,9 +1698,17 @@ out:
        return err;
 }
 
-/*
- * Create a hardlink
- * N.B. After this call _both_ ffhp and tfhp need an fh_put
+/**
+ * nfsd_link - create a link
+ * @rqstp: RPC transaction context
+ * @ffhp: the file handle of the directory where the new link is to be created
+ * @name: the filename of the new link
+ * @len: the length of @name in octets
+ * @tfhp: the file handle of an existing file object
+ *
+ * After this call _both_ ffhp and tfhp need an fh_put.
+ *
+ * Returns a generic NFS status code in network byte-order.
  */
 __be32
 nfsd_link(struct svc_rqst *rqstp, struct svc_fh *ffhp,
@@ -1708,6 +1716,7 @@ nfsd_link(struct svc_rqst *rqstp, struct svc_fh *ffhp,
 {
        struct dentry   *ddir, *dnew, *dold;
        struct inode    *dirp;
+       int             type;
        __be32          err;
        int             host_err;
 
@@ -1727,11 +1736,11 @@ nfsd_link(struct svc_rqst *rqstp, struct svc_fh *ffhp,
        if (isdotent(name, len))
                goto out;
 
+       err = nfs_ok;
+       type = d_inode(tfhp->fh_dentry)->i_mode & S_IFMT;
        host_err = fh_want_write(tfhp);
-       if (host_err) {
-               err = nfserrno(host_err);
+       if (host_err)
                goto out;
-       }
 
        ddir = ffhp->fh_dentry;
        dirp = d_inode(ddir);
@@ -1739,7 +1748,7 @@ nfsd_link(struct svc_rqst *rqstp, struct svc_fh *ffhp,
 
        dnew = lookup_one_len(name, ddir, len);
        if (IS_ERR(dnew)) {
-               err = nfserrno(PTR_ERR(dnew));
+               host_err = PTR_ERR(dnew);
                goto out_unlock;
        }
 
@@ -1755,17 +1764,26 @@ nfsd_link(struct svc_rqst *rqstp, struct svc_fh *ffhp,
        fh_fill_post_attrs(ffhp);
        inode_unlock(dirp);
        if (!host_err) {
-               err = nfserrno(commit_metadata(ffhp));
-               if (!err)
-                       err = nfserrno(commit_metadata(tfhp));
-       } else {
-               err = nfserrno(host_err);
+               host_err = commit_metadata(ffhp);
+               if (!host_err)
+                       host_err = commit_metadata(tfhp);
        }
+
        dput(dnew);
 out_drop_write:
        fh_drop_write(tfhp);
+       if (host_err == -EBUSY) {
+               /*
+                * See RFC 8881 Section 18.9.4 para 1-2: NFSv4 LINK
+                * wants a status unique to the object type.
+                */
+               if (type != S_IFDIR)
+                       err = nfserr_file_open;
+               else
+                       err = nfserr_acces;
+       }
 out:
-       return err;
+       return err != nfs_ok ? err : nfserrno(host_err);
 
 out_dput:
        dput(dnew);