FAILED: patch "[PATCH] smb: client: hold server info until cifsd exits" failed to apply to 5.10-stable tree

index 73b49dcb5215..d3ca688b6aba 100644
@@ -16,6 +16,7 @@
 #include <linux/scatterlist.h>
 #include <linux/mm.h>
 #include <linux/mempool.h>
+#include <linux/refcount.h>
 #include <linux/workqueue.h>
 #include <linux/utsname.h>
 #include <linux/sched/mm.h>

@@ -681,6 +682,7 @@ struct TCP_Server_Info {
 	spinlock_t srv_lock;  /* protect anything here that is not protected */
 	__u64 conn_id; /* connection identifier (useful for debugging) */
 	int srv_count; /* reference counter */
+	refcount_t obj_refs; /* struct lifetime: srv_count users + cifsd */
 	int rfc1001_sessinit; /* whether to estasblish netbios session */
 	bool with_rfc1001; /* if netbios session is used */
 	/* 15 character server name + 0x20 16th byte indicating type = srv */

index c3614c077746..e68fffb2ab2e 100644
@@ -1083,6 +1083,19 @@ cifs_enable_signing(struct TCP_Server_Info *server, bool mnt_sign_required)
 	return 0;
 }
 
+static void cifs_tcp_server_put(struct TCP_Server_Info *server)
+{
+	if (!refcount_dec_and_test(&server->obj_refs))
+		return;
+
+	cifs_crypto_secmech_release(server);
+	kfree_sensitive(server->session_key.response);
+	put_net(cifs_net_ns(server));
+	kfree(server->leaf_fullpath);
+	kfree(server->hostname);
+	kfree_sensitive(server);
+}
+
 static noinline_for_stack void
 clean_demultiplex_info(struct TCP_Server_Info *server)
 {

@@ -1168,14 +1181,11 @@ clean_demultiplex_info(struct TCP_Server_Info *server)
 		 */
 	}
 
-	put_net(cifs_net_ns(server));
-	kfree(server->leaf_fullpath);
-	kfree(server->hostname);
-	kfree_sensitive(server);
-
 	length = atomic_dec_return(&tcpSesAllocCount);
 	if (length > 0)
 		mempool_resize(cifs_req_poolp, length + cifs_min_rcv);
+
+	cifs_tcp_server_put(server);
 }
 
 static int

@@ -1751,7 +1761,7 @@ cifs_put_tcp_session(struct TCP_Server_Info *server, int from_reconnect)
 	else
 		cancel_delayed_work_sync(&server->reconnect);
 
-	/* For secondary channels, we pick up ref-count on the primary server */
+	/* For secondary channels, drop the reference on the primary server */
 	if (SERVER_IS_CHAN(server))
 		cifs_put_tcp_session(server->primary_server, from_reconnect);
 

@@ -1759,15 +1769,11 @@ cifs_put_tcp_session(struct TCP_Server_Info *server, int from_reconnect)
 	server->tcpStatus = CifsExiting;
 	spin_unlock(&server->srv_lock);
 
-	cifs_crypto_secmech_release(server);
-
-	kfree_sensitive(server->session_key.response);
-	server->session_key.response = NULL;
-	server->session_key.len = 0;
-
 	task = xchg(&server->tsk, NULL);
 	if (task)
 		send_sig(SIGKILL, task, 1);
+
+	cifs_tcp_server_put(server);
 }
 
 struct TCP_Server_Info *

@@ -1789,6 +1795,7 @@ cifs_get_tcp_session(struct smb3_fs_context *ctx,
 		rc = -ENOMEM;
 		goto out_err;
 	}
+	refcount_set(&tcp_ses->obj_refs, 1);
 
 	tcp_ses->hostname = kstrdup(ctx->server_hostname, GFP_KERNEL);
 	if (!tcp_ses->hostname) {

@@ -1927,6 +1934,8 @@ smbd_connected:
 		module_put(THIS_MODULE);
 		goto out_err_crypto_release;
 	}
+	/* Keep the server alive until the demultiplex thread has exited */
+	refcount_inc(&tcp_ses->obj_refs);
 	/* thread created, put it on the list */
 	spin_lock(&cifs_tcp_ses_lock);
 	list_add(&tcp_ses->tcp_ses_list, &cifs_tcp_ses_list);

index 8a5cdf4ba0ae6..05f68bf0a4a68 100644
@@ -25,6 +25,7 @@
 #include <linux/scatterlist.h>
 #include <linux/mm.h>
 #include <linux/mempool.h>
+#include <linux/refcount.h>
 #include <linux/workqueue.h>
 #include <linux/fcntl.h>
 #include "cifs_fs_sb.h"

@@ -674,6 +675,7 @@ struct TCP_Server_Info {
 	struct list_head tcp_ses_list;
 	struct list_head smb_ses_list;
 	int srv_count; /* reference counter */
+	refcount_t obj_refs; /* struct lifetime: srv_count users + cifsd */
 	/* 15 character server name + 0x20 16th byte indicating type = srv */
 	char server_RFC1001_name[RFC1001_NAME_LEN_WITH_NULL];
 	struct smb_version_operations	*ops;

index db54cbbe8cc5e..dedcc00e3b675 100644
@@ -880,6 +880,18 @@ handle_mid(struct mid_q_entry *mid, struct TCP_Server_Info *server,
 	dequeue_mid(mid, malformed);
 }
 
+static void cifs_tcp_server_put(struct TCP_Server_Info *server)
+{
+	if (!refcount_dec_and_test(&server->obj_refs))
+		return;
+
+	cifs_crypto_secmech_release(server);
+	kfree_sensitive(server->session_key.response);
+	put_net(cifs_net_ns(server));
+	kfree(server->hostname);
+	kfree_sensitive(server);
+}
+
 static void clean_demultiplex_info(struct TCP_Server_Info *server)
 {
 	int length;

@@ -964,12 +976,11 @@ static void clean_demultiplex_info(struct TCP_Server_Info *server)
 		 */
 	}
 
-	kfree(server->hostname);
-	kfree(server);
-
 	length = atomic_dec_return(&tcpSesAllocCount);
 	if (length > 0)
 		mempool_resize(cifs_req_poolp, length + cifs_min_rcv);
+
+	cifs_tcp_server_put(server);
 }
 
 static int

@@ -2496,8 +2507,6 @@ cifs_put_tcp_session(struct TCP_Server_Info *server, int from_reconnect)
 		return;
 	}
 
-	put_net(cifs_net_ns(server));
-
 	list_del_init(&server->tcp_ses_list);
 	spin_unlock(&cifs_tcp_ses_lock);
 

@@ -2518,16 +2527,13 @@ cifs_put_tcp_session(struct TCP_Server_Info *server, int from_reconnect)
 	server->tcpStatus = CifsExiting;
 	spin_unlock(&GlobalMid_Lock);
 
-	cifs_crypto_secmech_release(server);
 	cifs_fscache_release_client_cookie(server);
 
-	kfree(server->session_key.response);
-	server->session_key.response = NULL;
-	server->session_key.len = 0;
-
 	task = xchg(&server->tsk, NULL);
 	if (task)
 		send_sig(SIGKILL, task, 1);
+
+	cifs_tcp_server_put(server);
 }
 
 struct TCP_Server_Info *

@@ -2548,6 +2554,7 @@ cifs_get_tcp_session(struct smb_vol *volume_info)
 		rc = -ENOMEM;
 		goto out_err;
 	}
+	refcount_set(&tcp_ses->obj_refs, 1);
 
 	tcp_ses->ops = volume_info->ops;
 	tcp_ses->vals = volume_info->vals;

@@ -2635,6 +2642,8 @@ cifs_get_tcp_session(struct smb_vol *volume_info)
 	 * this will succeed. No need for try_module_get().
 	 */
 	__module_get(THIS_MODULE);
+	/* Keep the server alive until the demultiplex thread has exited */
+	refcount_inc(&tcp_ses->obj_refs);
 	tcp_ses->tsk = kthread_run(cifs_demultiplex_thread,
 				  tcp_ses, "cifsd");
 	if (IS_ERR(tcp_ses->tsk)) {