[PATCH 15/16] nfsd4: close open-deleg/unlink/rename race

["J. Bruce Fields" <bfields-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

From: "J. Bruce Fields" <bfields-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>

If a file is unlinked or renamed between the time when we do the local
open and the time when we get the delegation, then we will return to the
client indicating that it holds a delegation even though the file no
longer exists under the name it was open under.

But a client performing an open-by-name, when it is returned a
delegation, must be able to assume that the file is still linked at the
name it was opened under.

So, pass the parent filehandle into the delegation and lease-setting
code, and use it to re-lookup the file after we get the lease.

Signed-off-by: J. Bruce Fields <bfields-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 fs/nfsd/nfs4proc.c  |    2 +-
 fs/nfsd/nfs4state.c |   52 +++++++++++++++++++++++++++++++++++++++++++--------
 fs/nfsd/xdr4.h      |    3 ++-
 3 files changed, 47 insertions(+), 10 deletions(-)

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 4c0cbeb..f44b29d 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -457,7 +457,7 @@ nfsd4_open(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	 * successful, it (1) truncates the file if open->op_truncate was
 	 * set, (2) sets open->op_stateid, (3) sets open->op_delegation.
 	 */
-	status = nfsd4_process_open2(rqstp, resfh, open);
+	status = nfsd4_process_open2(rqstp, resfh, open, &cstate->current_fh);
 	WARN_ON(status && open->op_created);
 out:
 	if (resfh && resfh != &cstate->current_fh) {
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 7c91b6c..193f2bb 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -3018,7 +3018,28 @@ static struct file_lock *nfs4_alloc_init_lease(struct nfs4_delegation *dp, int f
 	return fl;
 }
 
-static int nfs4_setlease(struct nfs4_delegation *dp)
+static bool nfsd4_name_still_same(struct svc_fh *parent, struct nfsd4_open *open, struct dentry *dentry)
+{
+	struct xdr_netobj *name = &open->op_fname;
+	struct dentry *res;
+	bool ret;
+
+	if (parent->fh_dentry == dentry)
+		/* This was an open by filehandle, we don't care: */
+		return true;
+	if (nfsd_mountpoint(dentry, parent->fh_export))
+		/* We assume those never change */
+		return true;
+	mutex_lock(&parent->fh_dentry->d_inode->i_mutex); /* XXX? */
+	res = lookup_one_len(name->data, parent->fh_dentry, name->len);
+	mutex_unlock(&parent->fh_dentry->d_inode->i_mutex);
+	ret = res == dentry;
+	if (!IS_ERR(res))
+		dput(res);
+	return ret;
+}
+
+static int nfs4_setlease(struct nfs4_delegation *dp, struct nfsd4_open *open, struct svc_fh *parent)
 {
 	struct nfs4_file *fp = dp->dl_file;
 	struct file_lock *fl;
@@ -3031,23 +3052,37 @@ static int nfs4_setlease(struct nfs4_delegation *dp)
 	status = vfs_setlease(fl->fl_file, fl->fl_type, &fl);
 	if (status)
 		goto out_free;
+	if (!nfsd4_name_still_same(parent, open, fl->fl_file->f_dentry))
+		goto out_unlease;
+	spin_lock(&recall_lock);
+	if (fp->fi_had_conflict)
+		/*
+		 * whoops, already broken, but before we got a chance to
+		 * install our delegation; never mind:
+		 */
+		 goto out_unlock;
+	list_add(&dp->dl_perfile, &fp->fi_delegations);
+	spin_unlock(&recall_lock);
 	list_add(&dp->dl_perclnt, &dp->dl_stid.sc_client->cl_delegations);
 	fp->fi_lease = fl;
 	fp->fi_deleg_file = get_file(fl->fl_file);
 	atomic_set(&fp->fi_delegees, 1);
-	list_add(&dp->dl_perfile, &fp->fi_delegations);
 	return 0;
+out_unlock:
+	spin_unlock(&recall_lock);
+out_unlease:
+	vfs_setlease(fl->fl_file, F_UNLCK, &fl);
 out_free:
 	locks_free_lock(fl);
 	return -ENOMEM;
 }
 
-static int nfs4_set_delegation(struct nfs4_delegation *dp)
+static int nfs4_set_delegation(struct nfs4_delegation *dp, struct nfsd4_open *open, struct svc_fh *parent)
 {
 	struct nfs4_file *fp = dp->dl_file;
 
 	if (!fp->fi_lease)
-		return nfs4_setlease(dp);
+		return nfs4_setlease(dp, open, parent);
 	spin_lock(&recall_lock);
 	if (fp->fi_had_conflict) {
 		spin_unlock(&recall_lock);
@@ -3089,7 +3124,8 @@ static void nfsd4_open_deleg_none_ext(struct nfsd4_open *open, int status)
  */
 static void
 nfs4_open_delegation(struct net *net, struct svc_fh *fh,
-		     struct nfsd4_open *open, struct nfs4_ol_stateid *stp)
+		     struct nfsd4_open *open, struct nfs4_ol_stateid *stp,
+		     struct svc_fh *parent)
 {
 	struct nfs4_delegation *dp;
 	struct nfs4_openowner *oo = container_of(stp->st_stateowner, struct nfs4_openowner, oo_owner);
@@ -3132,7 +3168,7 @@ nfs4_open_delegation(struct net *net, struct svc_fh *fh,
 	dp = alloc_init_deleg(oo->oo_owner.so_client, stp, fh);
 	if (dp == NULL)
 		goto out_no_deleg;
-	status = nfs4_set_delegation(dp);
+	status = nfs4_set_delegation(dp, open, parent);
 	if (status)
 		goto out_free;
 
@@ -3181,7 +3217,7 @@ static void nfsd4_deleg_xgrade_none_ext(struct nfsd4_open *open,
  * called with nfs4_lock_state() held.
  */
 __be32
-nfsd4_process_open2(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nfsd4_open *open)
+nfsd4_process_open2(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nfsd4_open *open, struct svc_fh *parent)
 {
 	struct nfsd4_compoundres *resp = rqstp->rq_resp;
 	struct nfs4_client *cl = open->op_openowner->oo_owner.so_client;
@@ -3250,7 +3286,7 @@ nfsd4_process_open2(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nf
 	* Attempt to hand out a delegation. No error return, because the
 	* OPEN succeeds even if we fail.
 	*/
-	nfs4_open_delegation(SVC_NET(rqstp), current_fh, open, stp);
+	nfs4_open_delegation(SVC_NET(rqstp), current_fh, open, stp, parent);
 nodeleg:
 	status = nfs_ok;
 
diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
index b3ed644..3058885 100644
--- a/fs/nfsd/xdr4.h
+++ b/fs/nfsd/xdr4.h
@@ -596,7 +596,8 @@ __be32 nfsd4_reclaim_complete(struct svc_rqst *, struct nfsd4_compound_state *,
 extern __be32 nfsd4_process_open1(struct nfsd4_compound_state *,
 		struct nfsd4_open *open, struct nfsd_net *nn);
 extern __be32 nfsd4_process_open2(struct svc_rqst *rqstp,
-		struct svc_fh *current_fh, struct nfsd4_open *open);
+		struct svc_fh *current_fh, struct nfsd4_open *open,
+		struct svc_fh *parent);
 extern void nfsd4_cleanup_open_state(struct nfsd4_open *open, __be32 status);
 extern __be32 nfsd4_open_confirm(struct svc_rqst *rqstp,
 		struct nfsd4_compound_state *, struct nfsd4_open_confirm *oc);
-- 
1.7.9.5

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