linux-kernel - Re: [PATCH 2/5] seccomp: Introduce addfd ioctl to seccomp user notifier

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Date:   Mon, 25 May 2020 01:39:19 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Sargun Dhillon <sargun@...gun.me>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux Containers <containers@...ts.linux-foundation.org>,
        Linux API <linux-api@...r.kernel.org>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Tycho Andersen <tycho@...ho.ws>,
        Kees Cook <keescook@...omium.org>,
        Aleksa Sarai <cyphar@...har.com>,
        Jeffrey Vander Stoep <jeffv@...gle.com>,
        Jann Horn <jannh@...gle.com>, Robert Sesek <rsesek@...gle.com>,
        Chris Palmer <palmer@...gle.com>,
        Matt Denton <mpdenton@...gle.com>,
        Kees Cook <keescook@...gle.com>
Subject: Re: [PATCH 2/5] seccomp: Introduce addfd ioctl to seccomp user
 notifier

On Sun, May 24, 2020 at 05:27:58PM -0700, Sargun Dhillon wrote:

> >         if (addfd->fd >= 0) {
> >                 ret = replace_fd(addfd->fd, addfd->file, addfd->flags);
> >         } else {
> >                 ret = get_unused_fd_flags(addfd->flags);
> >                 if (ret >= 0)
> >                         fd_install(ret, get_file(addfd->file));
					    ^^^^^^^^

> Wouldn't this result in consumption of reference in one case (fd_install),
> and the fd still having a reference in the replace_fd case?