[PATCH 4.15 103/202] nfsd: Detect unhashed stids in nfsd4_verify_open_stid()

[Greg Kroah-Hartman]

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

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

From: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>

commit 4f1764172a0aa7395d12b96cae640ca1438c5085 upstream.

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@xxxxxxxxxxxxxxx>
Tested-by: Checuk Lever <chuck.lever@xxxxxxxxxx>
Fixes: 659aefb68eca "nfsd: Ensure we don't recognise lock stateids..."
Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/nfsd/nfs4state.c |    1 +
 1 file changed, 1 insertion(+)

--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -3590,6 +3590,7 @@ nfsd4_verify_open_stid(struct nfs4_stid
 	switch (s->sc_type) {
 	default:
 		break;
+	case 0:
 	case NFS4_CLOSED_STID:
 	case NFS4_CLOSED_DELEG_STID:
 		ret = nfserr_bad_stateid;