linux-kernel - [PATCH 4.8 079/140] NFSv4: nfs4_copy_delegation_stateid() must fail if the delegation is invalid

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Date:   Wed, 26 Oct 2016 14:22:19 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Trond Myklebust <trond.myklebust@...marydata.com>,
        Oleg Drokin <green@...uxhacker.ru>,
        Anna Schumaker <Anna.Schumaker@...app.com>
Subject: [PATCH 4.8 079/140] NFSv4: nfs4_copy_delegation_stateid() must fail if the delegation is invalid

4.8-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Trond Myklebust <trond.myklebust@...marydata.com>

commit aa05c87f23efe417adc7ff9b4193b7201ec0dd79 upstream.

We must not allow the use of delegations that have been revoked or are
being returned.

Signed-off-by: Trond Myklebust <trond.myklebust@...marydata.com>
Fixes: 869f9dfa4d6d ("NFSv4: Fix races between nfs_remove_bad_delegation()...")
Signed-off-by: Trond Myklebust <trond.myklebust@...marydata.com>
Tested-by: Oleg Drokin <green@...uxhacker.ru>
Signed-off-by: Anna Schumaker <Anna.Schumaker@...app.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/nfs/delegation.c |   17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

--- a/fs/nfs/delegation.c
+++ b/fs/nfs/delegation.c
@@ -41,6 +41,17 @@ void nfs_mark_delegation_referenced(stru
 	set_bit(NFS_DELEGATION_REFERENCED, &delegation->flags);
 }
 
+static bool
+nfs4_is_valid_delegation(const struct nfs_delegation *delegation,
+		fmode_t flags)
+{
+	if (delegation != NULL && (delegation->type & flags) == flags &&
+	    !test_bit(NFS_DELEGATION_REVOKED, &delegation->flags) &&
+	    !test_bit(NFS_DELEGATION_RETURNING, &delegation->flags))
+		return true;
+	return false;
+}
+
 static int
 nfs4_do_check_delegation(struct inode *inode, fmode_t flags, bool mark)
 {
@@ -50,9 +61,7 @@ nfs4_do_check_delegation(struct inode *i
 	flags &= FMODE_READ|FMODE_WRITE;
 	rcu_read_lock();
 	delegation = rcu_dereference(NFS_I(inode)->delegation);
-	if (delegation != NULL && (delegation->type & flags) == flags &&
-	    !test_bit(NFS_DELEGATION_REVOKED, &delegation->flags) &&
-	    !test_bit(NFS_DELEGATION_RETURNING, &delegation->flags)) {
+	if (nfs4_is_valid_delegation(delegation, flags)) {
 		if (mark)
 			nfs_mark_delegation_referenced(delegation);
 		ret = 1;
@@ -894,7 +903,7 @@ bool nfs4_copy_delegation_stateid(struct
 	flags &= FMODE_READ|FMODE_WRITE;
 	rcu_read_lock();
 	delegation = rcu_dereference(nfsi->delegation);
-	ret = (delegation != NULL && (delegation->type & flags) == flags);
+	ret = nfs4_is_valid_delegation(delegation, flags);
 	if (ret) {
 		nfs4_stateid_copy(dst, &delegation->stateid);
 		nfs_mark_delegation_referenced(delegation);