On Fri, May 29, 2020 at 6:31 AM Christian Brauner
[off-list ref] wrote:

quoted

quoted

+           /* Check if we were woken up by a addfd message */
+           addfd = list_first_entry_or_null(&n.addfd,
+                                            struct seccomp_kaddfd, list);
+           if (addfd && n.state != SECCOMP_NOTIFY_REPLIED) {
+                   seccomp_handle_addfd(addfd);
+                   mutex_unlock(&match->notify_lock);
+                   goto wait;
+           }
            ret = n.val;
            err = n.error;
            flags = n.flags;
    }

+   /* If there were any pending addfd calls, clear them out */
+   list_for_each_entry_safe(addfd, tmp, &n.addfd, list) {
+           /* The process went away before we got a chance to handle it */
+           addfd->ret = -ESRCH;
+           list_del_init(&addfd->list);
+           complete(&addfd->completion);
+   }

I forgot to ask this in my first review before, don't you need a
complete(&addfd->completion) call in seccomp_notify_release() before
freeing it?

When complete(&knotif->ready) is called in seccomp_notify_release,
subsequently the notifier (seccomp_do_user_notification) will be woken up and
it'll fail this check:
if (addfd && n.state != SECCOMP_NOTIFY_REPLIED)

Falling through to:
/* If there were any pending addfd calls, clear them out */
list_for_each_entry_safe(addfd, tmp, &n.addfd, list) {
    /* The process went away before we got a chance to handle it */
    addfd->ret = -ESRCH;
    list_del_init(&addfd->list);
    complete(&addfd->completion);
}

Although ESRCH isn't the "right" response, this fall through behaviour
should work.