Merge tag '6.9-rc2-smb3-client-fixes' of git://git.samba.org/sfrench/cifs-2.6

Pull smb client fixes from Steve French:

 - fix to retry close to avoid potential handle leaks when server
   returns EBUSY

 - DFS fixes including a fix for potential use after free

 - fscache fix

 - minor strncpy cleanup

 - reconnect race fix

 - deal with various possible UAF race conditions tearing sessions down

* tag '6.9-rc2-smb3-client-fixes' of git://git.samba.org/sfrench/cifs-2.6:
  smb: client: fix potential UAF in cifs_signal_cifsd_for_reconnect()
  smb: client: fix potential UAF in smb2_is_network_name_deleted()
  smb: client: fix potential UAF in is_valid_oplock_break()
  smb: client: fix potential UAF in smb2_is_valid_oplock_break()
  smb: client: fix potential UAF in smb2_is_valid_lease_break()
  smb: client: fix potential UAF in cifs_stats_proc_show()
  smb: client: fix potential UAF in cifs_stats_proc_write()
  smb: client: fix potential UAF in cifs_dump_full_key()
  smb: client: fix potential UAF in cifs_debug_files_proc_show()
  smb3: retrying on failed server close
  smb: client: serialise cifs_construct_tcon() with cifs_mount_mutex
  smb: client: handle DFS tcons in cifs_construct_tcon()
  smb: client: refresh referral without acquiring refpath_lock
  smb: client: guarantee refcounted children from parent session
  cifs: Fix caching to try to do open O_WRONLY as rdwr on server
  smb: client: fix UAF in smb2_reconnect_server()
  smb: client: replace deprecated strncpy with strscpy

22 files changed, 369 insertions, 178 deletions

diff --git a/fs/smb/client/cached_dir.c b/fs/smb/client/cached_dir.c
index a0017724d52393..13a9d7acf8f8ec 100644
--- a/fs/smb/client/cached_dir.c
+++ b/fs/smb/client/cached_dir.c
@@ -417,6 +417,7 @@ smb2_close_cached_fid(struct kref *ref)
 {
 	struct cached_fid *cfid = container_of(ref, struct cached_fid,
 					       refcount);
+	int rc;
 
 	spin_lock(&cfid->cfids->cfid_list_lock);
 	if (cfid->on_list) {
@@ -430,9 +431,10 @@ smb2_close_cached_fid(struct kref *ref)
 	cfid->dentry = NULL;
 
 	if (cfid->is_open) {
-		SMB2_close(0, cfid->tcon, cfid->fid.persistent_fid,
+		rc = SMB2_close(0, cfid->tcon, cfid->fid.persistent_fid,
 			   cfid->fid.volatile_fid);
-		atomic_dec(&cfid->tcon->num_remote_opens);
+		if (rc != -EBUSY && rc != -EAGAIN)
+			atomic_dec(&cfid->tcon->num_remote_opens);
 	}
 
 	free_cached_dir(cfid);
diff --git a/fs/smb/client/cifs_debug.c b/fs/smb/client/cifs_debug.c
index 226d4835c92db8..c71ae5c043060e 100644
--- a/fs/smb/client/cifs_debug.c
+++ b/fs/smb/client/cifs_debug.c
@@ -250,6 +250,8 @@ static int cifs_debug_files_proc_show(struct seq_file *m, void *v)
 	spin_lock(&cifs_tcp_ses_lock);
 	list_for_each_entry(server, &cifs_tcp_ses_list, tcp_ses_list) {
 		list_for_each_entry(ses, &server->smb_ses_list, smb_ses_list) {
+			if (cifs_ses_exiting(ses))
+				continue;
 			list_for_each_entry(tcon, &ses->tcon_list, tcon_list) {
 				spin_lock(&tcon->open_file_lock);
 				list_for_each_entry(cfile, &tcon->openFileList, tlist) {
@@ -676,6 +678,8 @@ static ssize_t cifs_stats_proc_write(struct file *file,
 			}
 #endif /* CONFIG_CIFS_STATS2 */
 			list_for_each_entry(ses, &server->smb_ses_list, smb_ses_list) {
+				if (cifs_ses_exiting(ses))
+					continue;
 				list_for_each_entry(tcon, &ses->tcon_list, tcon_list) {
 					atomic_set(&tcon->num_smbs_sent, 0);
 					spin_lock(&tcon->stat_lock);
@@ -755,6 +759,8 @@ static int cifs_stats_proc_show(struct seq_file *m, void *v)
 			}
 #endif /* STATS2 */
 		list_for_each_entry(ses, &server->smb_ses_list, smb_ses_list) {
+			if (cifs_ses_exiting(ses))
+				continue;
 			list_for_each_entry(tcon, &ses->tcon_list, tcon_list) {
 				i++;
 				seq_printf(m, "\n%d) %s", i, tcon->tree_name);
diff --git a/fs/smb/client/cifsfs.c b/fs/smb/client/cifsfs.c
index aa6f1ecb7c0e8f..d41eedbff674ab 100644
--- a/fs/smb/client/cifsfs.c
+++ b/fs/smb/client/cifsfs.c
@@ -156,6 +156,7 @@ struct workqueue_struct	*decrypt_wq;
 struct workqueue_struct	*fileinfo_put_wq;
 struct workqueue_struct	*cifsoplockd_wq;
 struct workqueue_struct	*deferredclose_wq;
+struct workqueue_struct	*serverclose_wq;
 __u32 cifs_lock_secret;
 
 /*
@@ -1888,6 +1889,13 @@ init_cifs(void)
 		goto out_destroy_cifsoplockd_wq;
 	}
 
+	serverclose_wq = alloc_workqueue("serverclose",
+					   WQ_FREEZABLE|WQ_MEM_RECLAIM, 0);
+	if (!serverclose_wq) {
+		rc = -ENOMEM;
+		goto out_destroy_serverclose_wq;
+	}
+
 	rc = cifs_init_inodecache();
 	if (rc)
 		goto out_destroy_deferredclose_wq;
@@ -1962,6 +1970,8 @@ out_destroy_decrypt_wq:
 	destroy_workqueue(decrypt_wq);
 out_destroy_cifsiod_wq:
 	destroy_workqueue(cifsiod_wq);
+out_destroy_serverclose_wq:
+	destroy_workqueue(serverclose_wq);
 out_clean_proc:
 	cifs_proc_clean();
 	return rc;
@@ -1991,6 +2001,7 @@ exit_cifs(void)
 	destroy_workqueue(cifsoplockd_wq);
 	destroy_workqueue(decrypt_wq);
 	destroy_workqueue(fileinfo_put_wq);
+	destroy_workqueue(serverclose_wq);
 	destroy_workqueue(cifsiod_wq);
 	cifs_proc_clean();
 }
diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h
index 7ed9d05f6890b4..f6a302205f89c4 100644
--- a/fs/smb/client/cifsglob.h
+++ b/fs/smb/client/cifsglob.h
@@ -442,10 +442,10 @@ struct smb_version_operations {
 	/* set fid protocol-specific info */
 	void (*set_fid)(struct cifsFileInfo *, struct cifs_fid *, __u32);
 	/* close a file */
-	void (*close)(const unsigned int, struct cifs_tcon *,
+	int (*close)(const unsigned int, struct cifs_tcon *,
 		      struct cifs_fid *);
 	/* close a file, returning file attributes and timestamps */
-	void (*close_getattr)(const unsigned int xid, struct cifs_tcon *tcon,
+	int (*close_getattr)(const unsigned int xid, struct cifs_tcon *tcon,
 		      struct cifsFileInfo *pfile_info);
 	/* send a flush request to the server */
 	int (*flush)(const unsigned int, struct cifs_tcon *, struct cifs_fid *);
@@ -1281,7 +1281,6 @@ struct cifs_tcon {
 	struct cached_fids *cfids;
 	/* BB add field for back pointer to sb struct(s)? */
 #ifdef CONFIG_CIFS_DFS_UPCALL
-	struct list_head dfs_ses_list;
 	struct delayed_work dfs_cache_work;
 #endif
 	struct delayed_work	query_interfaces; /* query interfaces workqueue job */
@@ -1440,6 +1439,7 @@ struct cifsFileInfo {
 	bool swapfile:1;
 	bool oplock_break_cancelled:1;
 	bool status_file_deleted:1; /* file has been deleted */
+	bool offload:1; /* offload final part of _put to a wq */
 	unsigned int oplock_epoch; /* epoch from the lease break */
 	__u32 oplock_level; /* oplock/lease level from the lease break */
 	int count;
@@ -1448,6 +1448,7 @@ struct cifsFileInfo {
 	struct cifs_search_info srch_inf;
 	struct work_struct oplock_break; /* work for oplock breaks */
 	struct work_struct put; /* work for the final part of _put */
+	struct work_struct serverclose; /* work for serverclose */
 	struct delayed_work deferred;
 	bool deferred_close_scheduled; /* Flag to indicate close is scheduled */
 	char *symlink_target;
@@ -1804,7 +1805,6 @@ struct cifs_mount_ctx {
 	struct TCP_Server_Info *server;
 	struct cifs_ses *ses;
 	struct cifs_tcon *tcon;
-	struct list_head dfs_ses_list;
 };
 
 static inline void __free_dfs_info_param(struct dfs_info3_param *param)
@@ -2105,6 +2105,7 @@ extern struct workqueue_struct *decrypt_wq;
 extern struct workqueue_struct *fileinfo_put_wq;
 extern struct workqueue_struct *cifsoplockd_wq;
 extern struct workqueue_struct *deferredclose_wq;
+extern struct workqueue_struct *serverclose_wq;
 extern __u32 cifs_lock_secret;
 
 extern mempool_t *cifs_sm_req_poolp;
@@ -2324,4 +2325,14 @@ struct smb2_compound_vars {
 	struct kvec ea_iov;
 };
 
+static inline bool cifs_ses_exiting(struct cifs_ses *ses)
+{
+	bool ret;
+
+	spin_lock(&ses->ses_lock);
+	ret = ses->ses_status == SES_EXITING;
+	spin_unlock(&ses->ses_lock);
+	return ret;
+}
+
 #endif	/* _CIFS_GLOB_H */
diff --git a/fs/smb/client/cifsproto.h b/fs/smb/client/cifsproto.h
index 0723e1b57256b8..8e0a348f1f660e 100644
--- a/fs/smb/client/cifsproto.h
+++ b/fs/smb/client/cifsproto.h
@@ -725,31 +725,31 @@ struct super_block *cifs_get_tcon_super(struct cifs_tcon *tcon);
 void cifs_put_tcon_super(struct super_block *sb);
 int cifs_wait_for_server_reconnect(struct TCP_Server_Info *server, bool retry);
 
-/* Put references of @ses and @ses->dfs_root_ses */
+/* Put references of @ses and its children */
 static inline void cifs_put_smb_ses(struct cifs_ses *ses)
 {
-	struct cifs_ses *rses = ses->dfs_root_ses;
+	struct cifs_ses *next;
 
-	__cifs_put_smb_ses(ses);
-	if (rses)
-		__cifs_put_smb_ses(rses);
+	do {
+		next = ses->dfs_root_ses;
+		__cifs_put_smb_ses(ses);
+	} while ((ses = next));
 }
 
-/* Get an active reference of @ses and @ses->dfs_root_ses.
+/* Get an active reference of @ses and its children.
  *
  * NOTE: make sure to call this function when incrementing reference count of
  * @ses to ensure that any DFS root session attached to it (@ses->dfs_root_ses)
  * will also get its reference count incremented.
  *
- * cifs_put_smb_ses() will put both references, so call it when you're done.
+ * cifs_put_smb_ses() will put all references, so call it when you're done.
  */
 static inline void cifs_smb_ses_inc_refcount(struct cifs_ses *ses)
 {
 	lockdep_assert_held(&cifs_tcp_ses_lock);
 
-	ses->ses_count++;
-	if (ses->dfs_root_ses)
-		ses->dfs_root_ses->ses_count++;
+	for (; ses; ses = ses->dfs_root_ses)
+		ses->ses_count++;
 }
 
 static inline bool dfs_src_pathname_equal(const char *s1, const char *s2)
diff --git a/fs/smb/client/cifssmb.c b/fs/smb/client/cifssmb.c
index 5aee555515730d..23b5709ddc311c 100644
--- a/fs/smb/client/cifssmb.c
+++ b/fs/smb/client/cifssmb.c
@@ -5854,10 +5854,8 @@ SetEARetry:
 	parm_data->list.EA_flags = 0;
 	/* we checked above that name len is less than 255 */
 	parm_data->list.name_len = (__u8)name_len;
-	/* EA names are always ASCII */
-	if (ea_name)
-		strncpy(parm_data->list.name, ea_name, name_len);
-	parm_data->list.name[name_len] = '\0';
+	/* EA names are always ASCII and NUL-terminated */
+	strscpy(parm_data->list.name, ea_name ?: "", name_len + 1);
 	parm_data->list.value_len = cpu_to_le16(ea_value_len);
 	/* caller ensures that ea_value_len is less than 64K but
 	we need to ensure that it fits within the smb */
diff --git a/fs/smb/client/connect.c b/fs/smb/client/connect.c
index 9b85b5341822e7..85679ae106fd50 100644
--- a/fs/smb/client/connect.c
+++ b/fs/smb/client/connect.c
@@ -175,6 +175,8 @@ cifs_signal_cifsd_for_reconnect(struct TCP_Server_Info *server,
 
 	spin_lock(&cifs_tcp_ses_lock);
 	list_for_each_entry(ses, &pserver->smb_ses_list, smb_ses_list) {
+		if (cifs_ses_exiting(ses))
+			continue;
 		spin_lock(&ses->chan_lock);
 		for (i = 0; i < ses->chan_count; i++) {
 			if (!ses->chans[i].server)
@@ -232,7 +234,13 @@ cifs_mark_tcp_ses_conns_for_reconnect(struct TCP_Server_Info *server,
 
 	spin_lock(&cifs_tcp_ses_lock);
 	list_for_each_entry_safe(ses, nses, &pserver->smb_ses_list, smb_ses_list) {
-		/* check if iface is still active */
+		spin_lock(&ses->ses_lock);
+		if (ses->ses_status == SES_EXITING) {
+			spin_unlock(&ses->ses_lock);
+			continue;
+		}
+		spin_unlock(&ses->ses_lock);
+
 		spin_lock(&ses->chan_lock);
 		if (cifs_ses_get_chan_index(ses, server) ==
 		    CIFS_INVAL_CHAN_INDEX) {
@@ -1860,6 +1868,9 @@ static int match_session(struct cifs_ses *ses, struct smb3_fs_context *ctx)
 	    ctx->sectype != ses->sectype)
 		return 0;
 
+	if (ctx->dfs_root_ses != ses->dfs_root_ses)
+		return 0;
+
 	/*
 	 * If an existing session is limited to less channels than
 	 * requested, it should not be reused
@@ -1963,31 +1974,6 @@ out:
 	return rc;
 }
 
-/**
- * cifs_free_ipc - helper to release the session IPC tcon
- * @ses: smb session to unmount the IPC from
- *
- * Needs to be called everytime a session is destroyed.
- *
- * On session close, the IPC is closed and the server must release all tcons of the session.
- * No need to send a tree disconnect here.
- *
- * Besides, it will make the server to not close durable and resilient files on session close, as
- * specified in MS-SMB2 3.3.5.6 Receiving an SMB2 LOGOFF Request.
- */
-static int
-cifs_free_ipc(struct cifs_ses *ses)
-{
-	struct cifs_tcon *tcon = ses->tcon_ipc;
-
-	if (tcon == NULL)
-		return 0;
-
-	tconInfoFree(tcon);
-	ses->tcon_ipc = NULL;
-	return 0;
-}
-
 static struct cifs_ses *
 cifs_find_smb_ses(struct TCP_Server_Info *server, struct smb3_fs_context *ctx)
 {
@@ -2019,48 +2005,52 @@ cifs_find_smb_ses(struct TCP_Server_Info *server, struct smb3_fs_context *ctx)
 void __cifs_put_smb_ses(struct cifs_ses *ses)
 {
 	struct TCP_Server_Info *server = ses->server;
+	struct cifs_tcon *tcon;
 	unsigned int xid;
 	size_t i;
+	bool do_logoff;
 	int rc;
 
+	spin_lock(&cifs_tcp_ses_lock);
 	spin_lock(&ses->ses_lock);
-	if (ses->ses_status == SES_EXITING) {
+	cifs_dbg(FYI, "%s: id=0x%llx ses_count=%d ses_status=%u ipc=%s\n",
+		 __func__, ses->Suid, ses->ses_count, ses->ses_status,
+		 ses->tcon_ipc ? ses->tcon_ipc->tree_name : "none");
+	if (ses->ses_status == SES_EXITING || --ses->ses_count > 0) {
 		spin_unlock(&ses->ses_lock);
+		spin_unlock(&cifs_tcp_ses_lock);
 		return;
 	}
-	spin_unlock(&ses->ses_lock);
+	/* ses_count can never go negative */
+	WARN_ON(ses->ses_count < 0);
 
-	cifs_dbg(FYI, "%s: ses_count=%d\n", __func__, ses->ses_count);
-	cifs_dbg(FYI,
-		 "%s: ses ipc: %s\n", __func__, ses->tcon_ipc ? ses->tcon_ipc->tree_name : "NONE");
+	spin_lock(&ses->chan_lock);
+	cifs_chan_clear_need_reconnect(ses, server);
+	spin_unlock(&ses->chan_lock);
 
-	spin_lock(&cifs_tcp_ses_lock);
-	if (--ses->ses_count > 0) {
-		spin_unlock(&cifs_tcp_ses_lock);
-		return;
-	}
-	spin_lock(&ses->ses_lock);
-	if (ses->ses_status == SES_GOOD)
-		ses->ses_status = SES_EXITING;
+	do_logoff = ses->ses_status == SES_GOOD && server->ops->logoff;
+	ses->ses_status = SES_EXITING;
+	tcon = ses->tcon_ipc;
+	ses->tcon_ipc = NULL;
 	spin_unlock(&ses->ses_lock);
 	spin_unlock(&cifs_tcp_ses_lock);
 
-	/* ses_count can never go negative */
-	WARN_ON(ses->ses_count < 0);
-
-	spin_lock(&ses->ses_lock);
-	if (ses->ses_status == SES_EXITING && server->ops->logoff) {
-		spin_unlock(&ses->ses_lock);
-		cifs_free_ipc(ses);
+	/*
+	 * On session close, the IPC is closed and the server must release all
+	 * tcons of the session.  No need to send a tree disconnect here.
+	 *
+	 * Besides, it will make the server to not close durable and resilient
+	 * files on session close, as specified in MS-SMB2 3.3.5.6 Receiving an
+	 * SMB2 LOGOFF Request.
+	 */
+	tconInfoFree(tcon);
+	if (do_logoff) {
 		xid = get_xid();
 		rc = server->ops->logoff(xid, ses);
 		if (rc)
 			cifs_server_dbg(VFS, "%s: Session Logoff failure rc=%d\n",
 				__func__, rc);
 		_free_xid(xid);
-	} else {
-		spin_unlock(&ses->ses_lock);
-		cifs_free_ipc(ses);
 	}
 
 	spin_lock(&cifs_tcp_ses_lock);
@@ -2373,9 +2363,9 @@ cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb3_fs_context *ctx)
 	 * need to lock before changing something in the session.
 	 */
 	spin_lock(&cifs_tcp_ses_lock);
+	if (ctx->dfs_root_ses)
+		cifs_smb_ses_inc_refcount(ctx->dfs_root_ses);
 	ses->dfs_root_ses = ctx->dfs_root_ses;
-	if (ses->dfs_root_ses)
-		ses->dfs_root_ses->ses_count++;
 	list_add(&ses->smb_ses_list, &server->smb_ses_list);
 	spin_unlock(&cifs_tcp_ses_lock);
 
@@ -3326,6 +3316,9 @@ void cifs_mount_put_conns(struct cifs_mount_ctx *mnt_ctx)
 		cifs_put_smb_ses(mnt_ctx->ses);
 	else if (mnt_ctx->server)
 		cifs_put_tcp_session(mnt_ctx->server, 0);
+	mnt_ctx->ses = NULL;
+	mnt_ctx->tcon = NULL;
+	mnt_ctx->server = NULL;
 	mnt_ctx->cifs_sb->mnt_cifs_flags &= ~CIFS_MOUNT_POSIX_PATHS;
 	free_xid(mnt_ctx->xid);
 }
@@ -3604,8 +3597,6 @@ int cifs_mount(struct cifs_sb_info *cifs_sb, struct smb3_fs_context *ctx)
 	bool isdfs;
 	int rc;
 
-	INIT_LIST_HEAD(&mnt_ctx.dfs_ses_list);
-
 	rc = dfs_mount_share(&mnt_ctx, &isdfs);
 	if (rc)
 		goto error;
@@ -3636,7 +3627,6 @@ out:
 	return rc;
 
 error:
-	dfs_put_root_smb_sessions(&mnt_ctx.dfs_ses_list);
 	cifs_mount_put_conns(&mnt_ctx);
 	return rc;
 }
@@ -3651,6 +3641,18 @@ int cifs_mount(struct cifs_sb_info *cifs_sb, struct smb3_fs_context *ctx)
 		goto error;
 
 	rc = cifs_mount_get_tcon(&mnt_ctx);
+	if (!rc) {
+		/*
+		 * Prevent superblock from being created with any missing
+		 * connections.
+		 */
+		if (WARN_ON(!mnt_ctx.server))
+			rc = -EHOSTDOWN;
+		else if (WARN_ON(!mnt_ctx.ses))
+			rc = -EACCES;
+		else if (WARN_ON(!mnt_ctx.tcon))
+			rc = -ENOENT;
+	}
 	if (rc)
 		goto error;
 
@@ -3988,13 +3990,14 @@ cifs_set_vol_auth(struct smb3_fs_context *ctx, struct cifs_ses *ses)
 }
 
 static struct cifs_tcon *
-cifs_construct_tcon(struct cifs_sb_info *cifs_sb, kuid_t fsuid)
+__cifs_construct_tcon(struct cifs_sb_info *cifs_sb, kuid_t fsuid)
 {
 	int rc;
 	struct cifs_tcon *master_tcon = cifs_sb_master_tcon(cifs_sb);
 	struct cifs_ses *ses;
 	struct cifs_tcon *tcon = NULL;
 	struct smb3_fs_context *ctx;
+	char *origin_fullpath = NULL;
 
 	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
 	if (ctx == NULL)
@@ -4018,6 +4021,7 @@ cifs_construct_tcon(struct cifs_sb_info *cifs_sb, kuid_t fsuid)
 	ctx->sign = master_tcon->ses->sign;
 	ctx->seal = master_tcon->seal;
 	ctx->witness = master_tcon->use_witness;
+	ctx->dfs_root_ses = master_tcon->ses->dfs_root_ses;
 
 	rc = cifs_set_vol_auth(ctx, master_tcon->ses);
 	if (rc) {
@@ -4037,12 +4041,39 @@ cifs_construct_tcon(struct cifs_sb_info *cifs_sb, kuid_t fsuid)
 		goto out;
 	}
 
+#ifdef CONFIG_CIFS_DFS_UPCALL
+	spin_lock(&master_tcon->tc_lock);
+	if (master_tcon->origin_fullpath) {
+		spin_unlock(&master_tcon->tc_lock);
+		origin_fullpath = dfs_get_path(cifs_sb, cifs_sb->ctx->source);
+		if (IS_ERR(origin_fullpath)) {
+			tcon = ERR_CAST(origin_fullpath);
+			origin_fullpath = NULL;
+			cifs_put_smb_ses(ses);
+			goto out;
+		}
+	} else {
+		spin_unlock(&master_tcon->tc_lock);
+	}
+#endif
+
 	tcon = cifs_get_tcon(ses, ctx);
 	if (IS_ERR(tcon)) {
 		cifs_put_smb_ses(ses);
 		goto out;
 	}
 
+#ifdef CONFIG_CIFS_DFS_UPCALL
+	if (origin_fullpath) {
+		spin_lock(&tcon->tc_lock);
+		tcon->origin_fullpath = origin_fullpath;
+		spin_unlock(&tcon->tc_lock);
+		origin_fullpath = NULL;
+		queue_delayed_work(dfscache_wq, &tcon->dfs_cache_work,
+				   dfs_cache_get_ttl() * HZ);
+	}
+#endif
+
 #ifdef CONFIG_CIFS_ALLOW_INSECURE_LEGACY
 	if (cap_unix(ses))
 		reset_cifs_unix_caps(0, tcon, NULL, ctx);
@@ -4051,11 +4082,23 @@ cifs_construct_tcon(struct cifs_sb_info *cifs_sb, kuid_t fsuid)
 out:
 	kfree(ctx->username);
 	kfree_sensitive(ctx->password);
+	kfree(origin_fullpath);
 	kfree(ctx);
 
 	return tcon;
 }
 
+static struct cifs_tcon *
+cifs_construct_tcon(struct cifs_sb_info *cifs_sb, kuid_t fsuid)
+{
+	struct cifs_tcon *ret;
+
+	cifs_mount_lock();
+	ret = __cifs_construct_tcon(cifs_sb, fsuid);
+	cifs_mount_unlock();
+	return ret;
+}
+
 struct cifs_tcon *
 cifs_sb_master_tcon(struct cifs_sb_info *cifs_sb)
 {
diff --git a/fs/smb/client/dfs.c b/fs/smb/client/dfs.c
index 449c59830039bc..3ec965547e3d4d 100644
--- a/fs/smb/client/dfs.c
+++ b/fs/smb/client/dfs.c
@@ -66,33 +66,20 @@ static int get_session(struct cifs_mount_ctx *mnt_ctx, const char *full_path)
 }
 
 /*
- * Track individual DFS referral servers used by new DFS mount.
- *
- * On success, their lifetime will be shared by final tcon (dfs_ses_list).
- * Otherwise, they will be put by dfs_put_root_smb_sessions() in cifs_mount().
+ * Get an active reference of @ses so that next call to cifs_put_tcon() won't
+ * release it as any new DFS referrals must go through its IPC tcon.
  */
-static int add_root_smb_session(struct cifs_mount_ctx *mnt_ctx)
+static void add_root_smb_session(struct cifs_mount_ctx *mnt_ctx)
 {
 	struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
-	struct dfs_root_ses *root_ses;
 	struct cifs_ses *ses = mnt_ctx->ses;
 
 	if (ses) {
-		root_ses = kmalloc(sizeof(*root_ses), GFP_KERNEL);
-		if (!root_ses)
-			return -ENOMEM;
-
-		INIT_LIST_HEAD(&root_ses->list);
-
 		spin_lock(&cifs_tcp_ses_lock);
 		cifs_smb_ses_inc_refcount(ses);
 		spin_unlock(&cifs_tcp_ses_lock);
-		root_ses->ses = ses;
-		list_add_tail(&root_ses->list, &mnt_ctx->dfs_ses_list);
 	}
-	/* Select new DFS referral server so that new referrals go through it */
 	ctx->dfs_root_ses = ses;
-	return 0;
 }
 
 static inline int parse_dfs_target(struct smb3_fs_context *ctx,
@@ -185,11 +172,8 @@ again:
 					continue;
 			}
 
-			if (is_refsrv) {
-				rc = add_root_smb_session(mnt_ctx);
-				if (rc)
-					goto out;
-			}
+			if (is_refsrv)
+				add_root_smb_session(mnt_ctx);
 
 			rc = ref_walk_advance(rw);
 			if (!rc) {
@@ -232,6 +216,7 @@ static int __dfs_mount_share(struct cifs_mount_ctx *mnt_ctx)
 	struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
 	struct cifs_tcon *tcon;
 	char *origin_fullpath;
+	bool new_tcon = true;
 	int rc;
 
 	origin_fullpath = dfs_get_path(cifs_sb, ctx->source);
@@ -239,6 +224,18 @@ static int __dfs_mount_share(struct cifs_mount_ctx *mnt_ctx)
 		return PTR_ERR(origin_fullpath);
 
 	rc = dfs_referral_walk(mnt_ctx);
+	if (!rc) {
+		/*
+		 * Prevent superblock from being created with any missing
+		 * connections.
+		 */
+		if (WARN_ON(!mnt_ctx->server))
+			rc = -EHOSTDOWN;
+		else if (WARN_ON(!mnt_ctx->ses))
+			rc = -EACCES;
+		else if (WARN_ON(!mnt_ctx->tcon))
+			rc = -ENOENT;
+	}
 	if (rc)
 		goto out;
 
@@ -247,15 +244,14 @@ static int __dfs_mount_share(struct cifs_mount_ctx *mnt_ctx)
 	if (!tcon->origin_fullpath) {
 		tcon->origin_fullpath = origin_fullpath;
 		origin_fullpath = NULL;
+	} else {
+		new_tcon = false;
 	}
 	spin_unlock(&tcon->tc_lock);
 
-	if (list_empty(&tcon->dfs_ses_list)) {
-		list_replace_init(&mnt_ctx->dfs_ses_list, &tcon->dfs_ses_list);
+	if (new_tcon) {
 		queue_delayed_work(dfscache_wq, &tcon->dfs_cache_work,
 				   dfs_cache_get_ttl() * HZ);
-	} else {
-		dfs_put_root_smb_sessions(&mnt_ctx->dfs_ses_list);
 	}
 
 out:
@@ -298,7 +294,6 @@ int dfs_mount_share(struct cifs_mount_ctx *mnt_ctx, bool *isdfs)
 	if (rc)
 		return rc;
 
-	ctx->dfs_root_ses = mnt_ctx->ses;
 	/*
 	 * If called with 'nodfs' mount option, then skip DFS resolving.  Otherwise unconditionally
 	 * try to get an DFS referral (even cached) to determine whether it is an DFS mount.
@@ -324,7 +319,9 @@ int dfs_mount_share(struct cifs_mount_ctx *mnt_ctx, bool *isdfs)
 
 	*isdfs = true;
 	add_root_smb_session(mnt_ctx);
-	return __dfs_mount_share(mnt_ctx);
+	rc = __dfs_mount_share(mnt_ctx);
+	dfs_put_root_smb_sessions(mnt_ctx);
+	return rc;
 }
 
 /* Update dfs referral path of superblock */
diff --git a/fs/smb/client/dfs.h b/fs/smb/client/dfs.h
index 875ab7ae57fcdf..e5c4dcf837503a 100644
--- a/fs/smb/client/dfs.h
+++ b/fs/smb/client/dfs.h
@@ -7,7 +7,9 @@
 #define _CIFS_DFS_H
 
 #include "cifsglob.h"
+#include "cifsproto.h"
 #include "fs_context.h"
+#include "dfs_cache.h"
 #include "cifs_unicode.h"
 #include <linux/namei.h>
 
@@ -114,11 +116,6 @@ static inline void ref_walk_set_tgt_hint(struct dfs_ref_walk *rw)
 				       ref_walk_tit(rw));
 }
 
-struct dfs_root_ses {
-	struct list_head list;
-	struct cifs_ses *ses;
-};
-
 int dfs_parse_target_referral(const char *full_path, const struct dfs_info3_param *ref,
 			      struct smb3_fs_context *ctx);
 int dfs_mount_share(struct cifs_mount_ctx *mnt_ctx, bool *isdfs);
@@ -133,20 +130,32 @@ static inline int dfs_get_referral(struct cifs_mount_ctx *mnt_ctx, const char *p
 {
 	struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
 	struct cifs_sb_info *cifs_sb = mnt_ctx->cifs_sb;
+	struct cifs_ses *rses = ctx->dfs_root_ses ?: mnt_ctx->ses;
 
-	return dfs_cache_find(mnt_ctx->xid, ctx->dfs_root_ses, cifs_sb->local_nls,
+	return dfs_cache_find(mnt_ctx->xid, rses, cifs_sb->local_nls,
 			      cifs_remap(cifs_sb), path, ref, tl);
 }
 
-static inline void dfs_put_root_smb_sessions(struct list_head *head)
+/*
+ * cifs_get_smb_ses() already guarantees an active reference of
+ * @ses->dfs_root_ses when a new session is created, so we need to put extra
+ * references of all DFS root sessions that were used across the mount process
+ * in dfs_mount_share().
+ */
+static inline void dfs_put_root_smb_sessions(struct cifs_mount_ctx *mnt_ctx)
 {
-	struct dfs_root_ses *root, *tmp;
+	const struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
+	struct cifs_ses *ses = ctx->dfs_root_ses;
+	struct cifs_ses *cur;
+
+	if (!ses)
+		return;
 
-	list_for_each_entry_safe(root, tmp, head, list) {
-		list_del_init(&root->list);
-		cifs_put_smb_ses(root->ses);
-		kfree(root);
+	for (cur = ses; cur; cur = cur->dfs_root_ses) {
+		if (cur->dfs_root_ses)
+			cifs_put_smb_ses(cur->dfs_root_ses);
 	}
+	cifs_put_smb_ses(ses);
 }
 
 #endif /* _CIFS_DFS_H */
diff --git a/fs/smb/client/dfs_cache.c b/fs/smb/client/dfs_cache.c
index 508d831fabe378..11c8efecf7aa12 100644
--- a/fs/smb/client/dfs_cache.c
+++ b/fs/smb/client/dfs_cache.c
@@ -1172,8 +1172,8 @@ static bool is_ses_good(struct cifs_ses *ses)
 	return ret;
 }
 
-/* Refresh dfs referral of tcon and mark it for reconnect if needed */
-static int __refresh_tcon(const char *path, struct cifs_ses *ses, bool force_refresh)
+/* Refresh dfs referral of @ses and mark it for reconnect if needed */
+static void __refresh_ses_referral(struct cifs_ses *ses, bool force_refresh)
 {
 	struct TCP_Server_Info *server = ses->server;
 	DFS_CACHE_TGT_LIST(old_tl);
@@ -1181,10 +1181,21 @@ static int __refresh_tcon(const char *path, struct cifs_ses *ses, bool force_ref
 	bool needs_refresh = false;
 	struct cache_entry *ce;
 	unsigned int xid;
+	char *path = NULL;
 	int rc = 0;
 
 	xid = get_xid();
 
+	mutex_lock(&server->refpath_lock);
+	if (server->leaf_fullpath) {
+		path = kstrdup(server->leaf_fullpath + 1, GFP_ATOMIC);
+		if (!path)
+			rc = -ENOMEM;
+	}
+	mutex_unlock(&server->refpath_lock);
+	if (!path)
+		goto out;
+
 	down_read(&htable_rw_lock);
 	ce = lookup_cache_entry(path);
 	needs_refresh = force_refresh || IS_ERR(ce) || cache_entry_expired(ce);
@@ -1218,19 +1229,17 @@ out:
 	free_xid(xid);
 	dfs_cache_free_tgts(&old_tl);
 	dfs_cache_free_tgts(&new_tl);
-	return rc;
+	kfree(path);
 }
 
-static int refresh_tcon(struct cifs_tcon *tcon, bool force_refresh)
+static inline void refresh_ses_referral(struct cifs_ses *ses)
 {
-	struct TCP_Server_Info *server = tcon->ses->server;
-	struct cifs_ses *ses = tcon->ses;
+	__refresh_ses_referral(ses, false);
+}
 
-	mutex_lock(&server->refpath_lock);
-	if (server->leaf_fullpath)
-		__refresh_tcon(server->leaf_fullpath + 1, ses, force_refresh);
-	mutex_unlock(&server->refpath_lock);
-	return 0;
+static inline void force_refresh_ses_referral(struct cifs_ses *ses)
+{
+	__refresh_ses_referral(ses, true);
 }
 
 /**
@@ -1271,34 +1280,20 @@ int dfs_cache_remount_fs(struct cifs_sb_info *cifs_sb)
 	 */
 	cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_USE_PREFIX_PATH;
 
-	return refresh_tcon(tcon, true);
+	force_refresh_ses_referral(tcon->ses);
+	return 0;
 }
 
 /* Refresh all DFS referrals related to DFS tcon */
 void dfs_cache_refresh(struct work_struct *work)
 {
-	struct TCP_Server_Info *server;
-	struct dfs_root_ses *rses;
 	struct cifs_tcon *tcon;
 	struct cifs_ses *ses;
 
 	tcon = container_of(work, struct cifs_tcon, dfs_cache_work.work);
-	ses = tcon->ses;
-	server = ses->server;
 
-	mutex_lock(&server->refpath_lock);
-	if (server->leaf_fullpath)
-		__refresh_tcon(server->leaf_fullpath + 1, ses, false);
-	mutex_unlock(&server->refpath_lock);
-
-	list_for_each_entry(rses, &tcon->dfs_ses_list, list) {
-		ses = rses->ses;
-		server = ses->server;
-		mutex_lock(&server->refpath_lock);
-		if (server->leaf_fullpath)
-			__refresh_tcon(server->leaf_fullpath + 1, ses, false);
-		mutex_unlock(&server->refpath_lock);
-	}
+	for (ses = tcon->ses; ses; ses = ses->dfs_root_ses)
+		refresh_ses_referral(ses);
 
 	queue_delayed_work(dfscache_wq, &tcon->dfs_cache_work,
 			   atomic_read(&dfs_cache_ttl) * HZ);
diff --git a/fs/smb/client/dir.c b/fs/smb/client/dir.c
index d11dc3aa458ba2..864b194dbaa0a0 100644
--- a/fs/smb/client/dir.c
+++ b/fs/smb/client/dir.c
@@ -189,6 +189,7 @@ static int cifs_do_create(struct inode *inode, struct dentry *direntry, unsigned
 	int disposition;
 	struct TCP_Server_Info *server = tcon->ses->server;
 	struct cifs_open_parms oparms;
+	int rdwr_for_fscache = 0;
 
 	*oplock = 0;
 	if (tcon->ses->server->oplocks)
@@ -200,6 +201,10 @@ static int cifs_do_create(struct inode *inode, struct dentry *direntry, unsigned
 		return PTR_ERR(full_path);
 	}
 
+	/* If we're caching, we need to be able to fill in around partial writes. */
+	if (cifs_fscache_enabled(inode) && (oflags & O_ACCMODE) == O_WRONLY)
+		rdwr_for_fscache = 1;
+
 #ifdef CONFIG_CIFS_ALLOW_INSECURE_LEGACY
 	if (tcon->unix_ext && cap_unix(tcon->ses) && !tcon->broken_posix_open &&
 	    (CIFS_UNIX_POSIX_PATH_OPS_CAP &
@@ -276,6 +281,8 @@ static int cifs_do_create(struct inode *inode, struct dentry *direntry, unsigned
 		desired_access |= GENERIC_READ; /* is this too little? */
 	if (OPEN_FMODE(oflags) & FMODE_WRITE)
 		desired_access |= GENERIC_WRITE;
+	if (rdwr_for_fscache == 1)
+		desired_access |= GENERIC_READ;
 
 	disposition = FILE_OVERWRITE_IF;
 	if ((oflags & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL))
@@ -304,6 +311,7 @@ static int cifs_do_create(struct inode *inode, struct dentry *direntry, unsigned
 	if (!tcon->unix_ext && (mode & S_IWUGO) == 0)
 		create_options |= CREATE_OPTION_READONLY;
 
+retry_open:
 	oparms = (struct cifs_open_parms) {
 		.tcon = tcon,
 		.cifs_sb = cifs_sb,
@@ -317,8 +325,15 @@ static int cifs_do_create(struct inode *inode, struct dentry *direntry, unsigned
 	rc = server->ops->open(xid, &oparms, oplock, buf);
 	if (rc) {
 		cifs_dbg(FYI, "cifs_create returned 0x%x\n", rc);
+		if (rc == -EACCES && rdwr_for_fscache == 1) {
+			desired_access &= ~GENERIC_READ;
+			rdwr_for_fscache = 2;
+			goto retry_open;
+		}
 		goto out;
 	}
+	if (rdwr_for_fscache == 2)
+		cifs_invalidate_cache(inode, FSCACHE_INVAL_DIO_WRITE);
 
 #ifdef CONFIG_CIFS_ALLOW_INSECURE_LEGACY
 	/*
diff --git a/fs/smb/client/file.c b/fs/smb/client/file.c
index 16aadce492b2ec..9be37d0fe724e9 100644
--- a/fs/smb/client/file.c
+++ b/fs/smb/client/file.c
@@ -206,12 +206,12 @@ cifs_mark_open_files_invalid(struct cifs_tcon *tcon)
 	 */
 }
 
-static inline int cifs_convert_flags(unsigned int flags)
+static inline int cifs_convert_flags(unsigned int flags, int rdwr_for_fscache)
 {
 	if ((flags & O_ACCMODE) == O_RDONLY)
 		return GENERIC_READ;
 	else if ((flags & O_ACCMODE) == O_WRONLY)
-		return GENERIC_WRITE;
+		return rdwr_for_fscache == 1 ? (GENERIC_READ | GENERIC_WRITE) : GENERIC_WRITE;
 	else if ((flags & O_ACCMODE) == O_RDWR) {
 		/* GENERIC_ALL is too much permission to request
 		   can cause unnecessary access denied on create */
@@ -348,11 +348,16 @@ static int cifs_nt_open(const char *full_path, struct inode *inode, struct cifs_
 	int create_options = CREATE_NOT_DIR;
 	struct TCP_Server_Info *server = tcon->ses->server;
 	struct cifs_open_parms oparms;
+	int rdwr_for_fscache = 0;
 
 	if (!server->ops->open)
 		return -ENOSYS;
 
-	desired_access = cifs_convert_flags(f_flags);
+	/* If we're caching, we need to be able to fill in around partial writes. */
+	if (cifs_fscache_enabled(inode) && (f_flags & O_ACCMODE) == O_WRONLY)
+		rdwr_for_fscache = 1;
+
+	desired_access = cifs_convert_flags(f_flags, rdwr_for_fscache);
 
 /*********************************************************************
  *  open flag mapping table:
@@ -389,6 +394,7 @@ static int cifs_nt_open(const char *full_path, struct inode *inode, struct cifs_
 	if (f_flags & O_DIRECT)
 		create_options |= CREATE_NO_BUFFER;
 
+retry_open:
 	oparms = (struct cifs_open_parms) {
 		.tcon = tcon,
 		.cifs_sb = cifs_sb,
@@ -400,8 +406,16 @@ static int cifs_nt_open(const char *full_path, struct inode *inode, struct cifs_
 	};
 
 	rc = server->ops->open(xid, &oparms, oplock, buf);
-	if (rc)
+	if (rc) {
+		if (rc == -EACCES && rdwr_for_fscache == 1) {
+			desired_access = cifs_convert_flags(f_flags, 0);
+			rdwr_for_fscache = 2;
+			goto retry_open;
+		}
 		return rc;
+	}
+	if (rdwr_for_fscache == 2)
+		cifs_invalidate_cache(inode, FSCACHE_INVAL_DIO_WRITE);
 
 	/* TODO: Add support for calling posix query info but with passing in fid */
 	if (tcon->unix_ext)
@@ -445,6 +459,7 @@ cifs_down_write(struct rw_semaphore *sem)
 }
 
 static void cifsFileInfo_put_work(struct work_struct *work);
+void serverclose_work(struct work_struct *work);
 
 struct cifsFileInfo *cifs_new_fileinfo(struct cifs_fid *fid, struct file *file,
 				       struct tcon_link *tlink, __u32 oplock,
@@ -491,6 +506,7 @@ struct cifsFileInfo *cifs_new_fileinfo(struct cifs_fid *fid, struct file *file,
 	cfile->tlink = cifs_get_tlink(tlink);
 	INIT_WORK(&cfile->oplock_break, cifs_oplock_break);
 	INIT_WORK(&cfile->put, cifsFileInfo_put_work);
+	INIT_WORK(&cfile->serverclose, serverclose_work);
 	INIT_DELAYED_WORK(&cfile->deferred, smb2_deferred_work_close);
 	mutex_init(&cfile->fh_mutex);
 	spin_lock_init(&cfile->file_info_lock);
@@ -582,6 +598,40 @@ static void cifsFileInfo_put_work(struct work_struct *work)
 	cifsFileInfo_put_final(cifs_file);
 }
 
+void serverclose_work(struct work_struct *work)
+{
+	struct cifsFileInfo *cifs_file = container_of(work,
+			struct cifsFileInfo, serverclose);
+
+	struct cifs_tcon *tcon = tlink_tcon(cifs_file->tlink);
+
+	struct TCP_Server_Info *server = tcon->ses->server;
+	int rc = 0;
+	int retries = 0;
+	int MAX_RETRIES = 4;
+
+	do {
+		if (server->ops->close_getattr)
+			rc = server->ops->close_getattr(0, tcon, cifs_file);
+		else if (server->ops->close)
+			rc = server->ops->close(0, tcon, &cifs_file->fid);
+
+		if (rc == -EBUSY || rc == -EAGAIN) {
+			retries++;
+			msleep(250);
+		}
+	} while ((rc == -EBUSY || rc == -EAGAIN) && (retries < MAX_RETRIES)
+	);
+
+	if (retries == MAX_RETRIES)
+		pr_warn("Serverclose failed %d times, giving up\n", MAX_RETRIES);
+
+	if (cifs_file->offload)
+		queue_work(fileinfo_put_wq, &cifs_file->put);
+	else
+		cifsFileInfo_put_final(cifs_file);
+}
+
 /**
  * cifsFileInfo_put - release a reference of file priv data
  *
@@ -622,10 +672,13 @@ void _cifsFileInfo_put(struct cifsFileInfo *cifs_file,
 	struct cifs_fid fid = {};
 	struct cifs_pending_open open;
 	bool oplock_break_cancelled;
+	bool serverclose_offloaded = false;
 
 	spin_lock(&tcon->open_file_lock);
 	spin_lock(&cifsi->open_file_lock);
 	spin_lock(&cifs_file->file_info_lock);
+
+	cifs_file->offload = offload;
 	if (--cifs_file->count > 0) {
 		spin_unlock(&cifs_file->file_info_lock);
 		spin_unlock(&cifsi->open_file_lock);
@@ -667,13 +720,20 @@ void _cifsFileInfo_put(struct cifsFileInfo *cifs_file,
 	if (!tcon->need_reconnect && !cifs_file->invalidHandle) {
 		struct TCP_Server_Info *server = tcon->ses->server;
 		unsigned int xid;
+		int rc = 0;
 
 		xid = get_xid();
 		if (server->ops->close_getattr)
-			server->ops->close_getattr(xid, tcon, cifs_file);
+			rc = server->ops->close_getattr(xid, tcon, cifs_file);
 		else if (server->ops->close)
-			server->ops->close(xid, tcon, &cifs_file->fid);
+			rc = server->ops->close(xid, tcon, &cifs_file->fid);
 		_free_xid(xid);
+
+		if (rc == -EBUSY || rc == -EAGAIN) {
+			// Server close failed, hence offloading it as an async op
+			queue_work(serverclose_wq, &cifs_file->serverclose);
+			serverclose_offloaded = true;
+		}
 	}
 
 	if (oplock_break_cancelled)
@@ -681,10 +741,15 @@ void _cifsFileInfo_put(struct cifsFileInfo *cifs_file,
 
 	cifs_del_pending_open(&open);
 
-	if (offload)
-		queue_work(fileinfo_put_wq, &cifs_file->put);
-	else
-		cifsFileInfo_put_final(cifs_file);
+	// if serverclose has been offloaded to wq (on failure), it will
+	// handle offloading put as well. If serverclose not offloaded,
+	// we need to handle offloading put here.
+	if (!serverclose_offloaded) {
+		if (offload)
+			queue_work(fileinfo_put_wq, &cifs_file->put);
+		else
+			cifsFileInfo_put_final(cifs_file);
+	}
 }
 
 int cifs_open(struct inode *inode, struct file *file)
@@ -834,11 +899,11 @@ int cifs_open(struct inode *inode, struct file *file)
 use_cache:
 	fscache_use_cookie(cifs_inode_cookie(file_inode(file)),
 			   file->f_mode & FMODE_WRITE);
-	if (file->f_flags & O_DIRECT &&
-	    (!((file->f_flags & O_ACCMODE) != O_RDONLY) ||
-	     file->f_flags & O_APPEND))
-		cifs_invalidate_cache(file_inode(file),
-				      FSCACHE_INVAL_DIO_WRITE);
+	if (!(file->f_flags & O_DIRECT))
+		goto out;
+	if ((file->f_flags & (O_ACCMODE | O_APPEND)) == O_RDONLY)
+		goto out;
+	cifs_invalidate_cache(file_inode(file), FSCACHE_INVAL_DIO_WRITE);
 
 out:
 	free_dentry_path(page);
@@ -903,6 +968,7 @@ cifs_reopen_file(struct cifsFileInfo *cfile, bool can_flush)
 	int disposition = FILE_OPEN;
 	int create_options = CREATE_NOT_DIR;
 	struct cifs_open_parms oparms;
+	int rdwr_for_fscache = 0;
 
 	xid = get_xid();
 	mutex_lock(&cfile->fh_mutex);
@@ -966,7 +1032,11 @@ cifs_reopen_file(struct cifsFileInfo *cfile, bool can_flush)
 	}
 #endif /* CONFIG_CIFS_ALLOW_INSECURE_LEGACY */
 
-	desired_access = cifs_convert_flags(cfile->f_flags);
+	/* If we're caching, we need to be able to fill in around partial writes. */
+	if (cifs_fscache_enabled(inode) && (cfile->f_flags & O_ACCMODE) == O_WRONLY)
+		rdwr_for_fscache = 1;
+
+	desired_access = cifs_convert_flags(cfile->f_flags, rdwr_for_fscache);
 
 	/* O_SYNC also has bit for O_DSYNC so following check picks up either */
 	if (cfile->f_flags & O_SYNC)
@@ -978,6 +1048,7 @@ cifs_reopen_file(struct cifsFileInfo *cfile, bool can_flush)
 	if (server->ops->get_lease_key)
 		server->ops->get_lease_key(inode, &cfile->fid);
 
+retry_open:
 	oparms = (struct cifs_open_parms) {
 		.tcon = tcon,
 		.cifs_sb = cifs_sb,
@@ -1003,6 +1074,11 @@ cifs_reopen_file(struct cifsFileInfo *cfile, bool can_flush)
 		/* indicate that we need to relock the file */
 		oparms.reconnect = true;
 	}
+	if (rc == -EACCES && rdwr_for_fscache == 1) {
+		desired_access = cifs_convert_flags(cfile->f_flags, 0);
+		rdwr_for_fscache = 2;
+		goto retry_open;
+	}
 
 	if (rc) {
 		mutex_unlock(&cfile->fh_mutex);
@@ -1011,6 +1087,9 @@ cifs_reopen_file(struct cifsFileInfo *cfile, bool can_flush)
 		goto reopen_error_exit;
 	}
 
+	if (rdwr_for_fscache == 2)
+		cifs_invalidate_cache(inode, FSCACHE_INVAL_DIO_WRITE);
+
 #ifdef CONFIG_CIFS_ALLOW_INSECURE_LEGACY
 reopen_success:
 #endif /* CONFIG_CIFS_ALLOW_INSECURE_LEGACY */
diff --git a/fs/smb/client/fs_context.c b/fs/smb/client/fs_context.c
index bdcbe6ff2739ab..b7bfe705b2c498 100644
--- a/fs/smb/client/fs_context.c
+++ b/fs/smb/client/fs_context.c
@@ -37,7 +37,7 @@
 #include "rfc1002pdu.h"
 #include "fs_context.h"
 
-static DEFINE_MUTEX(cifs_mount_mutex);
+DEFINE_MUTEX(cifs_mount_mutex);
 
 static const match_table_t cifs_smb_version_tokens = {
 	{ Smb_1, SMB1_VERSION_STRING },
@@ -783,9 +783,9 @@ static int smb3_get_tree(struct fs_context *fc)
 
 	if (err)
 		return err;
-	mutex_lock(&cifs_mount_mutex);
+	cifs_mount_lock();
 	ret = smb3_get_tree_common(fc);
-	mutex_unlock(&cifs_mount_mutex);
+	cifs_mount_unlock();
 	return ret;
 }
 
diff --git a/fs/smb/client/fs_context.h b/fs/smb/client/fs_context.h
index 7863f2248c4df8..8a35645e0b65b2 100644
--- a/fs/smb/client/fs_context.h
+++ b/fs/smb/client/fs_context.h
@@ -304,4 +304,16 @@ extern void smb3_update_mnt_flags(struct cifs_sb_info *cifs_sb);
 #define MAX_CACHED_FIDS 16
 extern char *cifs_sanitize_prepath(char *prepath, gfp_t gfp);
 
+extern struct mutex cifs_mount_mutex;
+
+static inline void cifs_mount_lock(void)
+{
+	mutex_lock(&cifs_mount_mutex);
+}
+
+static inline void cifs_mount_unlock(void)
+{
+	mutex_unlock(&cifs_mount_mutex);
+}
+
 #endif
diff --git a/fs/smb/client/fscache.h b/fs/smb/client/fscache.h
index a3d73720914f88..1f2ea9f5cc9a8a 100644
--- a/fs/smb/client/fscache.h
+++ b/fs/smb/client/fscache.h
@@ -109,6 +109,11 @@ static inline void cifs_readahead_to_fscache(struct inode *inode,
 		__cifs_readahead_to_fscache(inode, pos, len);
 }
 
+static inline bool cifs_fscache_enabled(struct inode *inode)
+{
+	return fscache_cookie_enabled(cifs_inode_cookie(inode));
+}
+
 #else /* CONFIG_CIFS_FSCACHE */
 static inline
 void cifs_fscache_fill_coherency(struct inode *inode,
@@ -124,6 +129,7 @@ static inline void cifs_fscache_release_inode_cookie(struct inode *inode) {}
 static inline void cifs_fscache_unuse_inode_cookie(struct inode *inode, bool update) {}
 static inline struct fscache_cookie *cifs_inode_cookie(struct inode *inode) { return NULL; }
 static inline void cifs_invalidate_cache(struct inode *inode, unsigned int flags) {}
+static inline bool cifs_fscache_enabled(struct inode *inode) { return false; }
 
 static inline int cifs_fscache_query_occupancy(struct inode *inode,
 					       pgoff_t first, unsigned int nr_pages,
diff --git a/fs/smb/client/ioctl.c b/fs/smb/client/ioctl.c
index c012dfdba80d45..855ac5a62edfaa 100644
--- a/fs/smb/client/ioctl.c
+++ b/fs/smb/client/ioctl.c
@@ -247,7 +247,9 @@ static int cifs_dump_full_key(struct cifs_tcon *tcon, struct smb3_full_key_debug
 		spin_lock(&cifs_tcp_ses_lock);
 		list_for_each_entry(server_it, &cifs_tcp_ses_list, tcp_ses_list) {
 			list_for_each_entry(ses_it, &server_it->smb_ses_list, smb_ses_list) {
-				if (ses_it->Suid == out.session_id) {
+				spin_lock(&ses_it->ses_lock);
+				if (ses_it->ses_status != SES_EXITING &&
+				    ses_it->Suid == out.session_id) {
 					ses = ses_it;
 					/*
 					 * since we are using the session outside the crit
@@ -255,9 +257,11 @@ static int cifs_dump_full_key(struct cifs_tcon *tcon, struct smb3_full_key_debug
 					 * so increment its refcount
 					 */
 					cifs_smb_ses_inc_refcount(ses);
+					spin_unlock(&ses_it->ses_lock);
 					found = true;
 					goto search_end;
 				}
+				spin_unlock(&ses_it->ses_lock);
 			}
 		}
 search_end:
diff --git a/fs/smb/client/misc.c b/fs/smb/client/misc.c
index c3771fc81328ff..33ac4f8f5050c4 100644
--- a/fs/smb/client/misc.c
+++ b/fs/smb/client/misc.c
@@ -138,9 +138,6 @@ tcon_info_alloc(bool dir_leases_enabled)
 	atomic_set(&ret_buf->num_local_opens, 0);
 	atomic_set(&ret_buf->num_remote_opens, 0);
 	ret_buf->stats_from_time = ktime_get_real_seconds();
-#ifdef CONFIG_CIFS_DFS_UPCALL
-	INIT_LIST_HEAD(&ret_buf->dfs_ses_list);
-#endif
 
 	return ret_buf;
 }
@@ -156,9 +153,6 @@ tconInfoFree(struct cifs_tcon *tcon)
 	atomic_dec(&tconInfoAllocCount);
 	kfree(tcon->nativeFileSystem);
 	kfree_sensitive(tcon->password);
-#ifdef CONFIG_CIFS_DFS_UPCALL
-	dfs_put_root_smb_sessions(&tcon->dfs_ses_list);
-#endif
 	kfree(tcon->origin_fullpath);
 	kfree(tcon);
 }
@@ -487,6 +481,8 @@ is_valid_oplock_break(char *buffer, struct TCP_Server_Info *srv)
 	/* look up tcon based on tid & uid */
 	spin_lock(&cifs_tcp_ses_lock);
 	list_for_each_entry(ses, &pserver->smb_ses_list, smb_ses_list) {
+		if (cifs_ses_exiting(ses))
+			continue;
 		list_for_each_entry(tcon, &ses->tcon_list, tcon_list) {
 			if (tcon->tid != buf->Tid)
 				continue;
diff --git a/fs/smb/client/smb1ops.c b/fs/smb/client/smb1ops.c
index a9eaba8083b0d6..212ec6f66ec65b 100644
--- a/fs/smb/client/smb1ops.c
+++ b/fs/smb/client/smb1ops.c
@@ -753,11 +753,11 @@ cifs_set_fid(struct cifsFileInfo *cfile, struct cifs_fid *fid, __u32 oplock)
 	cinode->can_cache_brlcks = CIFS_CACHE_WRITE(cinode);
 }
 
-static void
+static int
 cifs_close_file(const unsigned int xid, struct cifs_tcon *tcon,
 		struct cifs_fid *fid)
 {
-	CIFSSMBClose(xid, tcon, fid->netfid);
+	return CIFSSMBClose(xid, tcon, fid->netfid);
 }
 
 static int
diff --git a/fs/smb/client/smb2misc.c b/fs/smb/client/smb2misc.c
index 82b84a4941dd2f..cc72be5a93a933 100644
--- a/fs/smb/client/smb2misc.c
+++ b/fs/smb/client/smb2misc.c
@@ -622,6 +622,8 @@ smb2_is_valid_lease_break(char *buffer, struct TCP_Server_Info *server)
 	/* look up tcon based on tid & uid */
 	spin_lock(&cifs_tcp_ses_lock);
 	list_for_each_entry(ses, &pserver->smb_ses_list, smb_ses_list) {
+		if (cifs_ses_exiting(ses))
+			continue;
 		list_for_each_entry(tcon, &ses->tcon_list, tcon_list) {
 			spin_lock(&tcon->open_file_lock);
 			cifs_stats_inc(
@@ -697,6 +699,8 @@ smb2_is_valid_oplock_break(char *buffer, struct TCP_Server_Info *server)
 	/* look up tcon based on tid & uid */
 	spin_lock(&cifs_tcp_ses_lock);
 	list_for_each_entry(ses, &pserver->smb_ses_list, smb_ses_list) {
+		if (cifs_ses_exiting(ses))
+			continue;
 		list_for_each_entry(tcon, &ses->tcon_list, tcon_list) {
 
 			spin_lock(&tcon->open_file_lock);
diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
index 2ed456948f34ca..b156eefa75d7cb 100644
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -1412,14 +1412,14 @@ smb2_set_fid(struct cifsFileInfo *cfile, struct cifs_fid *fid, __u32 oplock)
 	memcpy(cfile->fid.create_guid, fid->create_guid, 16);
 }
 
-static void
+static int
 smb2_close_file(const unsigned int xid, struct cifs_tcon *tcon,
 		struct cifs_fid *fid)
 {
-	SMB2_close(xid, tcon, fid->persistent_fid, fid->volatile_fid);
+	return SMB2_close(xid, tcon, fid->persistent_fid, fid->volatile_fid);
 }
 
-static void
+static int
 smb2_close_getattr(const unsigned int xid, struct cifs_tcon *tcon,
 		   struct cifsFileInfo *cfile)
 {
@@ -1430,7 +1430,7 @@ smb2_close_getattr(const unsigned int xid, struct cifs_tcon *tcon,
 	rc = __SMB2_close(xid, tcon, cfile->fid.persistent_fid,
 		   cfile->fid.volatile_fid, &file_inf);
 	if (rc)
-		return;
+		return rc;
 
 	inode = d_inode(cfile->dentry);
 
@@ -1459,6 +1459,7 @@ smb2_close_getattr(const unsigned int xid, struct cifs_tcon *tcon,
 
 	/* End of file and Attributes should not have to be updated on close */
 	spin_unlock(&inode->i_lock);
+	return rc;
 }
 
 static int
@@ -2480,6 +2481,8 @@ smb2_is_network_name_deleted(char *buf, struct TCP_Server_Info *server)
 
 	spin_lock(&cifs_tcp_ses_lock);
 	list_for_each_entry(ses, &pserver->smb_ses_list, smb_ses_list) {
+		if (cifs_ses_exiting(ses))
+			continue;
 		list_for_each_entry(tcon, &ses->tcon_list, tcon_list) {
 			if (tcon->tid == le32_to_cpu(shdr->Id.SyncId.TreeId)) {
 				spin_lock(&tcon->tc_lock);
@@ -3913,7 +3916,7 @@ smb21_set_oplock_level(struct cifsInodeInfo *cinode, __u32 oplock,
 		strcat(message, "W");
 	}
 	if (!new_oplock)
-		strncpy(message, "None", sizeof(message));
+		strscpy(message, "None");
 
 	cinode->oplock = new_oplock;
 	cifs_dbg(FYI, "%s Lease granted on inode %p\n", message,
diff --git a/fs/smb/client/smb2pdu.c b/fs/smb/client/smb2pdu.c
index 3ea688558e6c9b..c0c4933af5fc38 100644
--- a/fs/smb/client/smb2pdu.c
+++ b/fs/smb/client/smb2pdu.c
@@ -3628,9 +3628,9 @@ replay_again:
 			memcpy(&pbuf->network_open_info,
 			       &rsp->network_open_info,
 			       sizeof(pbuf->network_open_info));
+		atomic_dec(&tcon->num_remote_opens);
 	}
 
-	atomic_dec(&tcon->num_remote_opens);
 close_exit:
 	SMB2_close_free(&rqst);
 	free_rsp_buf(resp_buftype, rsp);
diff --git a/fs/smb/client/smb2transport.c b/fs/smb/client/smb2transport.c
index 5a3ca62d2f07f7..1d6e54f7879e6a 100644
--- a/fs/smb/client/smb2transport.c
+++ b/fs/smb/client/smb2transport.c
@@ -659,7 +659,7 @@ smb2_sign_rqst(struct smb_rqst *rqst, struct TCP_Server_Info *server)
 	}
 	spin_unlock(&server->srv_lock);
 	if (!is_binding && !server->session_estab) {
-		strncpy(shdr->Signature, "BSRSPYL", 8);
+		strscpy(shdr->Signature, "BSRSPYL");
 		return 0;
 	}