FAILED: patch "[PATCH] cifs: fix kref underflow in close_shroot()" failed to apply to 4.19-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 2f94a3125b8742b05a011d62b16f52eb8f9ebe1c Mon Sep 17 00:00:00 2001
From: Ronnie Sahlberg <lsahlber@redhat.com>
Date: Thu, 28 Mar 2019 11:20:02 +1000
Subject: [PATCH] cifs: fix kref underflow in close_shroot()

Fix a bug where we used to not initialize the cached fid structure at all
in open_shroot() if the open was successful but we did not get a lease.
This would leave the structure uninitialized and later when we close the handle
we would in close_shroot() try to kref_put() an uninitialized refcount.

Fix this by always initializing this structure if the open was successful
but only do the extra get() if we got a lease.
This extra get() is only used to hold the structure until we get a lease
break from the server at which point we will kref_put() it during lease
processing.

Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
CC: Stable <stable@vger.kernel.org>

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index 1022a3771e14..7cfafac255aa 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -717,20 +717,18 @@ int open_shroot(unsigned int xid, struct cifs_tcon *tcon, struct cifs_fid *pfid)
 	oparms.fid->mid = le64_to_cpu(o_rsp->sync_hdr.MessageId);
 #endif /* CIFS_DEBUG2 */
 
-	if (o_rsp->OplockLevel == SMB2_OPLOCK_LEVEL_LEASE)
-		oplock = smb2_parse_lease_state(server, o_rsp,
-						&oparms.fid->epoch,
-						oparms.fid->lease_key);
-	else
-		goto oshr_exit;
-
-
 	memcpy(tcon->crfid.fid, pfid, sizeof(struct cifs_fid));
 	tcon->crfid.tcon = tcon;
 	tcon->crfid.is_valid = true;
 	kref_init(&tcon->crfid.refcount);
-	kref_get(&tcon->crfid.refcount);
 
+	if (o_rsp->OplockLevel == SMB2_OPLOCK_LEVEL_LEASE) {
+		kref_get(&tcon->crfid.refcount);
+		oplock = smb2_parse_lease_state(server, o_rsp,
+						&oparms.fid->epoch,
+						oparms.fid->lease_key);
+	} else
+		goto oshr_exit;
 
 	qi_rsp = (struct smb2_query_info_rsp *)rsp_iov[1].iov_base;
 	if (le32_to_cpu(qi_rsp->OutputBufferLength) < sizeof(struct smb2_file_all_info))