From: Shyam Prasad N <sprasad@microsoft.com>
Date: Wed, 14 Jul 2021 23:00:00 -0500
Subject: [PATCH] cifs: added WARN_ON for all the count decrements
Git-commit: 16dd9b8c31aee7ae074fa3ee36a797e9ba9f7e4f
Patch-mainline: v5.14-rc2
References: bsc#1192606

We have a few ref counters srv_count, ses_count and
tc_count which we use for ref counting. Added a WARN_ON
during the decrement of each of these counters to make
sure that they don't go below their minimum values.

Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Acked-by: Enzo Matsumiya <ematsumiya@suse.de>
---
 fs/cifs/connect.c | 9 +++++++++
 fs/cifs/smb2ops.c | 2 ++
 2 files changed, 11 insertions(+)

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index a1e870232114..6b6c3e341b42 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -1295,6 +1295,9 @@ cifs_put_tcp_session(struct TCP_Server_Info *server, int from_reconnect)
 		return;
 	}
 
+	/* srv_count can never go negative */
+	WARN_ON(server->srv_count < 0);
+
 	put_net(cifs_net_ns(server));
 
 	list_del_init(&server->tcp_ses_list);
@@ -1654,6 +1657,9 @@ void cifs_put_smb_ses(struct cifs_ses *ses)
 	}
 	spin_unlock(&cifs_tcp_ses_lock);
 
+	/* ses_count can never go negative */
+	WARN_ON(ses->ses_count < 0);
+
 	spin_lock(&GlobalMid_Lock);
 	if (ses->status == CifsGood)
 		ses->status = CifsExiting;
@@ -2021,6 +2027,9 @@ cifs_put_tcon(struct cifs_tcon *tcon)
 		return;
 	}
 
+	/* tc_count can never go negative */
+	WARN_ON(tcon->tc_count < 0);
+
 	if (tcon->use_witness) {
 		int rc;
 
diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index 232d528df230..ba3c58e1f725 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -2910,6 +2910,8 @@ smb2_get_dfs_refer(const unsigned int xid, struct cifs_ses *ses,
 		/* ipc tcons are not refcounted */
 		spin_lock(&cifs_tcp_ses_lock);
 		tcon->tc_count--;
+		/* tc_count can never go negative */
+		WARN_ON(tcon->tc_count < 0);
 		spin_unlock(&cifs_tcp_ses_lock);
 	}
 	kfree(utf16_path);
-- 
2.33.1