nfsd: Ensure nfsv4 calls the underlying filesystem on LOCKT

Since nfsv4 allows LOCKT without an open, but the ->lock() method is a
file method, we fake up a struct file in the nfsv4 code with just the
fields we need initialized.  But we forgot to initialize the file
operations, with the result that LOCKT never results in a call to the
filesystem's ->lock() method (if it exists).

We could just add that one more initialization.  But this hack of faking
up a struct file with only some fields initialized seems the kind of
thing that might cause more problems in the future.  We should either do
an open and get a real struct file, or make lock-testing an inode (not a
file) method.

This patch does the former.

Reported-by: Marc Eshel <eshel@almaden.ibm.com>
Tested-by: Marc Eshel <eshel@almaden.ibm.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

1 files changed, 20 insertions, 10 deletions

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 06b89df92218..e62d0e3df8b3 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -2782,6 +2782,25 @@ out:
 }
 
 /*
+ * The NFSv4 spec allows a client to do a LOCKT without holding an OPEN,
+ * so we do a temporary open here just to get an open file to pass to
+ * vfs_test_lock.  (Arguably perhaps test_lock should be done with an
+ * inode operation.)
+ */
+static int nfsd_test_lock(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file_lock *lock)
+{
+        struct file *file;
+        int err;
+
+        err = nfsd_open(rqstp, fhp, S_IFREG, NFSD_MAY_READ, &file);
+        if (err)
+                return err;
+        err = vfs_test_lock(file, lock);
+        nfsd_close(file);
+        return err;
+}
+
+/*
  * LOCKT operation
  */
 __be32
@@ -2789,7 +2808,6 @@ nfsd4_lockt(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
             struct nfsd4_lockt *lockt)
 {
         struct inode *inode;
-        struct file file;
         struct file_lock file_lock;
         int error;
         __be32 status;
@@ -2847,16 +2865,8 @@ nfsd4_lockt(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 
         nfs4_transform_lock_offset(&file_lock);
 
-        /* vfs_test_lock uses the struct file _only_ to resolve the inode.
-         * since LOCKT doesn't require an OPEN, and therefore a struct
-         * file may not exist, pass vfs_test_lock a struct file with
-         * only the dentry:inode set.
-         */
-        memset(&file, 0, sizeof (struct file));
-        file.f_path.dentry = cstate->current_fh.fh_dentry;
-
         status = nfs_ok;
-        error = vfs_test_lock(&file, &file_lock);
+        error = nfsd_test_lock(rqstp, &cstate->current_fh, &file_lock);
         if (error) {
                 status = nfserrno(error);
                 goto out;