[PATCH] nfsd: Detect unhashed stids in nfsd4_verify_open_stid()

[Trond Myklebust <trond.myklebust@primarydata.com>]

The state of the stid is guaranteed by 2 locks:
- The nfs4_client 'cl_lock' spinlock
- The nfs4_ol_stateid 'st_mutex' mutex

so it is quite possible for the stid to be unhashed after lookup,
but before calling nfsd4_lock_ol_stateid(). So we do need to check
for a zero value for 'sc_type' in nfsd4_verify_open_stid().

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
---
 fs/nfsd/nfs4state.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 8d53d29161f5..b5bda115f6a9 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -3591,6 +3591,7 @@ nfsd4_verify_open_stid(struct nfs4_stid *s)
 	switch (s->sc_type) {
 	default:
 		break;
+	case 0:
 	case NFS4_CLOSED_STID:
 	case NFS4_CLOSED_DELEG_STID:
 		ret = nfserr_bad_stateid;
-- 
2.14.3