SMB3: Add missing locks to protect deferred close file list

cifs_del_deferred_close function has a critical section which modifies
the deferred close file list. We must acquire deferred_lock before
calling cifs_del_deferred_close function.

Fixes: ca08d0ea ("cifs: Fix memory leak on the deferred close")
Signed-off-by: Bharath SM <bharathsm@microsoft.com>
Acked-off-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Acked-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/misc.c

@@ -749,7 +749,9 @@ cifs_close_deferred_file(struct cifsInodeInfo *cifs_inode)
 	list_for_each_entry(cfile, &cifs_inode->openFileList, flist) {
 		if (delayed_work_pending(&cfile->deferred)) {
 			if (cancel_delayed_work(&cfile->deferred)) {
+				spin_lock(&cifs_inode->deferred_lock);
 				cifs_del_deferred_close(cfile);
+				spin_unlock(&cifs_inode->deferred_lock);
 
 				tmp_list = kmalloc(sizeof(struct file_list), GFP_ATOMIC);
 				if (tmp_list == NULL)
@@ -780,7 +782,9 @@ cifs_close_all_deferred_files(struct cifs_tcon *tcon)
 	list_for_each_entry(cfile, &tcon->openFileList, tlist) {
 		if (delayed_work_pending(&cfile->deferred)) {
 			if (cancel_delayed_work(&cfile->deferred)) {
+				spin_lock(&CIFS_I(d_inode(cfile->dentry))->deferred_lock);
 				cifs_del_deferred_close(cfile);
+				spin_unlock(&CIFS_I(d_inode(cfile->dentry))->deferred_lock);
 
 				tmp_list = kmalloc(sizeof(struct file_list), GFP_ATOMIC);
 				if (tmp_list == NULL)
@@ -815,7 +819,9 @@ cifs_close_deferred_file_under_dentry(struct cifs_tcon *tcon, const char *path)
 		if (strstr(full_path, path)) {
 			if (delayed_work_pending(&cfile->deferred)) {
 				if (cancel_delayed_work(&cfile->deferred)) {
+					spin_lock(&CIFS_I(d_inode(cfile->dentry))->deferred_lock);
 					cifs_del_deferred_close(cfile);
+					spin_unlock(&CIFS_I(d_inode(cfile->dentry))->deferred_lock);
 
 					tmp_list = kmalloc(sizeof(struct file_list), GFP_ATOMIC);
 					if (tmp_list == NULL)