From 22b464f8f7fff4d366e057bf5e5a51b12ce48bda Mon Sep 17 00:00:00 2001
From: Rohith Surabattula <rohiths@microsoft.com>
Date: Mon, 9 Aug 2021 09:32:46 +0000
Subject: [PATCH 2/2] cifs: Call close synchronously during unlink/rename/lease
 break.

During unlink/rename/lease break, deferred work for close is
scheduled immediately but in asynchronous manner which might
lead to race with actual(unlink/rename) commands.

This change will schedule close synchronously which will avoid
the race conditions with other commands.

Signed-off-by: Rohith Surabattula <rohiths@microsoft.com>
---
 fs/cifs/cifsglob.h |  5 +++++
 fs/cifs/file.c     | 35 +++++++++++++++++------------------
 fs/cifs/misc.c     | 46 ++++++++++++++++++++++++++++++++++------------
 3 files changed, 56 insertions(+), 30 deletions(-)

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index c0bfc2f01030..c6a9542ca281 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -1611,6 +1611,11 @@ struct dfs_info3_param {
 	int ttl;
 };
 
+struct file_list {
+	struct list_head list;
+	struct cifsFileInfo *cfile;
+};
+
 /*
  * common struct for holding inode info when searching for or updating an
  * inode with new info
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 0a72840a88f1..bb98fbdd22a9 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -4847,17 +4847,6 @@ void cifs_oplock_break(struct work_struct *work)
 		cifs_dbg(VFS, "Push locks rc = %d\n", rc);
 
 oplock_break_ack:
-	/*
-	 * releasing stale oplock after recent reconnect of smb session using
-	 * a now incorrect file handle is not a data integrity issue but do
-	 * not bother sending an oplock release if session to server still is
-	 * disconnected since oplock already released by the server
-	 */
-	if (!cfile->oplock_break_cancelled) {
-		rc = tcon->ses->server->ops->oplock_response(tcon, &cfile->fid,
-							     cinode);
-		cifs_dbg(FYI, "Oplock release rc = %d\n", rc);
-	}
 	/*
 	 * When oplock break is received and there are no active
 	 * file handles but cached, then schedule deferred close immediately.
@@ -4865,17 +4854,27 @@ void cifs_oplock_break(struct work_struct *work)
 	 */
 	spin_lock(&CIFS_I(inode)->deferred_lock);
 	is_deferred = cifs_is_deferred_close(cfile, &dclose);
+	spin_unlock(&CIFS_I(inode)->deferred_lock);
 	if (is_deferred &&
 	    cfile->deferred_close_scheduled &&
 	    delayed_work_pending(&cfile->deferred)) {
-		/*
-		 * If there is no pending work, mod_delayed_work queues new work.
-		 * So, Increase the ref count to avoid use-after-free.
-		 */
-		if (!mod_delayed_work(deferredclose_wq, &cfile->deferred, 0))
-			cifsFileInfo_get(cfile);
+		if (cancel_delayed_work(&cfile->deferred)) {
+			_cifsFileInfo_put(cfile, false, false);
+			goto oplock_break_done;
+		}
 	}
-	spin_unlock(&CIFS_I(inode)->deferred_lock);
+	/*
+	 * releasing stale oplock after recent reconnect of smb session using
+	 * a now incorrect file handle is not a data integrity issue but do
+	 * not bother sending an oplock release if session to server still is
+	 * disconnected since oplock already released by the server
+	 */
+	if (!cfile->oplock_break_cancelled) {
+		rc = tcon->ses->server->ops->oplock_response(tcon, &cfile->fid,
+							     cinode);
+		cifs_dbg(FYI, "Oplock release rc = %d\n", rc);
+	}
+oplock_break_done:
 	_cifsFileInfo_put(cfile, false /* do not wait for ourself */, false);
 	cifs_done_oplock_break(cinode);
 }
diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
index cdb1ec1461de..9469f1cf0b46 100644
--- a/fs/cifs/misc.c
+++ b/fs/cifs/misc.c
@@ -723,20 +723,32 @@ void
 cifs_close_deferred_file(struct cifsInodeInfo *cifs_inode)
 {
 	struct cifsFileInfo *cfile = NULL;
+	struct file_list *tmp_list, *tmp_next_list;
+	struct list_head file_head;
 
 	if (cifs_inode == NULL)
 		return;
 
+	INIT_LIST_HEAD(&file_head);
+	spin_lock(&cifs_inode->open_file_lock);
 	list_for_each_entry(cfile, &cifs_inode->openFileList, flist) {
 		if (delayed_work_pending(&cfile->deferred)) {
-			/*
-			 * If there is no pending work, mod_delayed_work queues new work.
-			 * So, Increase the ref count to avoid use-after-free.
-			 */
-			if (!mod_delayed_work(deferredclose_wq, &cfile->deferred, 0))
-				cifsFileInfo_get(cfile);
+			if (cancel_delayed_work(&cfile->deferred)) {
+				tmp_list = kmalloc(sizeof(struct file_list), GFP_ATOMIC);
+				if (tmp_list == NULL)
+					continue;
+				tmp_list->cfile = cfile;
+				list_add_tail(&tmp_list->list, &file_head);
+			}
 		}
 	}
+	spin_unlock(&cifs_inode->open_file_lock);
+
+	list_for_each_entry_safe(tmp_list, tmp_next_list, &file_head, list) {
+		_cifsFileInfo_put(tmp_list->cfile, true, false);
+		list_del(&tmp_list->list);
+		kfree(tmp_list);
+	}
 }
 
 void
@@ -744,20 +756,30 @@ cifs_close_all_deferred_files(struct cifs_tcon *tcon)
 {
 	struct cifsFileInfo *cfile;
 	struct list_head *tmp;
+	struct file_list *tmp_list, *tmp_next_list;
+	struct list_head file_head;
 
+	INIT_LIST_HEAD(&file_head);
 	spin_lock(&tcon->open_file_lock);
 	list_for_each(tmp, &tcon->openFileList) {
 		cfile = list_entry(tmp, struct cifsFileInfo, tlist);
 		if (delayed_work_pending(&cfile->deferred)) {
-			/*
-			 * If there is no pending work, mod_delayed_work queues new work.
-			 * So, Increase the ref count to avoid use-after-free.
-			 */
-			if (!mod_delayed_work(deferredclose_wq, &cfile->deferred, 0))
-				cifsFileInfo_get(cfile);
+			if (cancel_delayed_work(&cfile->deferred)) {
+				tmp_list = kmalloc(sizeof(struct file_list), GFP_ATOMIC);
+				if (tmp_list == NULL)
+					continue;
+				tmp_list->cfile = cfile;
+				list_add_tail(&tmp_list->list, &file_head);
+			}
 		}
 	}
 	spin_unlock(&tcon->open_file_lock);
+
+	list_for_each_entry_safe(tmp_list, tmp_next_list, &file_head, list) {
+		_cifsFileInfo_put(tmp_list->cfile, true, false);
+		list_del(&tmp_list->list);
+		kfree(tmp_list);
+	}
 }
 
 /* parses DFS refferal V3 structure
-- 
2.33.0.rc1

