Deleting files on SMB with read-only rights does not notify that delete is not possible

Steps to reproduce

1. Having an SMB mount with a folder containing big files. eg +2GB (video camera files)
2. Backend share is set to read-only for the user used
3. Try to delete a big file

Expected behaviour

Notification about delete is not possible.

Actual behaviour

The spinner turns, but nothing gets deleted, even waiting for a long time.

Note I:

There is read SMB traffic I can monitor on the backend, but I cant identify a location if/where it gets written to the local server.

Note II:

After looking around, I identified the problem. The SMB share (which I setup long time ago) is set to read-only on the backend for the used user (it is not a readonly mount!). It would be good to get a notification if the delete action has been triggered but is not possible instead of trying forever.

Note III:

There are NO log entries related to this action, not in nginx or ownCloud.

Server configuration

Operating system: Ubuntu 18.04

Web server: nginx

Database: MariaDB

PHP version: 7.3

ownCloud version: (10.4)

Updated from an older ownCloud or fresh install: updated

Where did you install ownCloud from: tar

Signing status (ownCloud 9.0 and above):
all green

The content of config/config.php:

{
    "system": {
        "instanceid": "ocbdscdhwdo8",
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "trusted_domains": [
            "xxxx"
        ],
        "datadirectory": "xxxx\/data",
        "overwrite.cli.url": "https:\/\/xxxx",
        "dbtype": "mysql",
        "version": "10.4.0.4",
        "dbname": "xxxx",
        "dbhost": "localhost",
        "dbtableprefix": "oc_",
        "mysql.utf8mb4": true,
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "logtimezone": "UTC",
        "installed": true,
        "filelocking.enabled": "true",
        "memcache.local": "\\OC\\Memcache\\Redis",
        "memcache.locking": "\\OC\\Memcache\\Redis",
        "memcache.distributed": "\\OC\\Memcache\\Redis",
        "redis": {
            "host": "\/var\/run\/redis\/redis-server.sock",
            "port": 0,
            "timeout": 0,
            "dbindex": 0
        },
        "filesystem_check_changes": 1,
        "excluded_directories": [
            ".snapshot",
            "~snapshot"
        ],
        "upgrade.automatic-app-update": true,
        "quota_include_external_storage": false,
        "mail_smtpmode": "smtp",
        "mail_from_address": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpsecure": "tls",
        "mail_domain": "***REMOVED SENSITIVE VALUE***",
        "mail_smtphost": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpport": "587",
        "mail_smtpauthtype": "LOGIN",
        "apps_paths": [
            {
                "path": "xxxx\/apps",
                "url": "\/apps",
                "writable": false
            },
            {
                "path": "xxxx\/apps-external",
                "url": "\/apps-external",
                "writable": true
            }
        ],
        "maintenance": false,
        "loglevel": 2,
        "theme": "",
        "show_server_hostname": false,
        "log_rotate_size": "20971520"
    }
}

List of activated apps:

Enabled:
  - activity: 2.5.3
  - comments: 0.3.0
  - configreport: 0.2.0
  - dav: 0.5.0
  - federatedfilesharing: 0.5.0
  - federation: 0.1.0
  - files: 1.5.2
  - files_clipboard: 1.0.2
  - files_external: 0.7.1
  - files_external_dropbox: 1.2.0
  - files_external_ftp: 0.2.1
  - files_mediaviewer: 1.0.2
  - files_pdfviewer: 0.11.1
  - files_sharing: 0.12.0
  - files_texteditor: 2.3.0
  - files_trashbin: 0.9.1
  - files_versions: 1.3.0
  - firstrunwizard: 1.2.0
  - market: 0.5.0
  - notifications: 0.5.0
  - provisioning_api: 0.5.0
  - systemtags: 0.3.0
  - updatenotification: 0.2.1
Disabled:
  - encryption
  - external
  - user_external

Are you using external storage, if yes which one: local/smb/ftp/gd/dp

Are you using encryption: no

Are you using an external user-backend, if yes which one: no

Client configuration

Browser: Opera

Operating system: W10x64

Logs

Web server error log

nothing relevant

ownCloud log (data/owncloud.log)

nothing relevant

Start by reproducing the delete action against the read-only SMB external storage described in the issue, then inspect the files app's delete handling and the resulting ownCloud and web-server logs. Trace where the request waits without an error response. Done means an attempted delete on an unwritable SMB share promptly shows a notification that deletion is not possible.