NFSv4: nfs4_copy_delegation_stateid() must fail if the delegation is invalid

We must not allow the use of delegations that have been revoked or are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

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Fixes: 869f9dfa4d6d ("NFSv4: Fix races between nfs_remove_bad_delegation()...")
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Cc: stable@vger.kernel.org # v3.19+
Tested-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

1 files changed, 13 insertions, 4 deletions

diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
index 86d2c748140b..b9c65421ed81 100644
--- a/fs/nfs/delegation.c
+++ b/fs/nfs/delegation.c
@@ -41,6 +41,17 @@ void nfs_mark_delegation_referenced(struct nfs_delegation *delegation)
         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 *inode, fmode_t flags, bool mark)
         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 inode *inode, fmode_t flags,
         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);