nfsd: vfs_mkdir() might succeed leaving dentry negative unhashed

That can (and does, on some filesystems) happen - ->mkdir() (and thus
vfs_mkdir()) can legitimately leave its argument negative and just
unhash it, counting upon the lookup to pick the object we'd created
next time we try to look at that name.

Some vfs_mkdir() callers forget about that possibility...

Acked-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 22 insertions, 0 deletions

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 2410b093a2e6..b0555d7d8200 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1201,6 +1201,28 @@ nfsd_create_locked(struct svc_rqst *rqstp, struct svc_fh *fhp,
                 break;
         case S_IFDIR:
                 host_err = vfs_mkdir(dirp, dchild, iap->ia_mode);
+                if (!host_err && unlikely(d_unhashed(dchild))) {
+                        struct dentry *d;
+                        d = lookup_one_len(dchild->d_name.name,
+                                           dchild->d_parent,
+                                           dchild->d_name.len);
+                        if (IS_ERR(d)) {
+                                host_err = PTR_ERR(d);
+                                break;
+                        }
+                        if (unlikely(d_is_negative(d))) {
+                                dput(d);
+                                err = nfserr_serverfault;
+                                goto out;
+                        }
+                        dput(resfhp->fh_dentry);
+                        resfhp->fh_dentry = dget(d);
+                        err = fh_update(resfhp);
+                        dput(dchild);
+                        dchild = d;
+                        if (err)
+                                goto out;
+                }
                 break;
         case S_IFCHR:
         case S_IFBLK: