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From: Al Viro <viro@zeniv.linux.org.uk>
To: Sargun Dhillon <sargun@sargun.me>
Cc: linux-kernel@vger.kernel.org,
	containers@lists.linux-foundation.org, linux-api@vger.kernel.org,
	christian.brauner@ubuntu.com, tycho@tycho.ws,
	keescook@chromium.org, cyphar@cyphar.com,
	Jeffrey Vander Stoep <jeffv@google.com>,
	jannh@google.com, rsesek@google.com, palmer@google.com,
	Matt Denton <mpdenton@google.com>,
	Kees Cook <keescook@google.com>
Subject: Re: [PATCH 2/5] seccomp: Introduce addfd ioctl to seccomp user notifier
Date: Mon, 25 May 2020 01:05:37 +0100
Message-ID: <20200525000537.GB23230@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20200524233942.8702-3-sargun@sargun.me>

On Sun, May 24, 2020 at 04:39:39PM -0700, Sargun Dhillon wrote:
> +static void seccomp_handle_addfd(struct seccomp_kaddfd *addfd)
> +{
> +	int ret;
> +
> +	/*
> +	 * Remove the notification, and reset the list pointers, indicating
> +	 * that it has been handled.
> +	 */
> +	list_del_init(&addfd->list);
> +
> +	ret = security_file_receive(addfd->file);
> +	if (ret)
> +		goto out;
> +
> +	if (addfd->fd >= 0) {
> +		ret = replace_fd(addfd->fd, addfd->file, addfd->flags);
> +		if (ret >= 0)
> +			fput(addfd->file);
> +	} else {
> +		ret = get_unused_fd_flags(addfd->flags);
> +		if (ret >= 0)
> +			fd_install(ret, addfd->file);

Bad refcounting rules.  *IF* we go with anything of that sort (and I'm not
convinced that the entire series makes sense), it's better to have more
uniform rules re reference consumption/disposal.

Make the destructor of addfd *ALWAYS* drop its reference.  And have this
function go

	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));
	}


  parent reply index

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-24 23:39 [PATCH 0/5] Add seccomp notifier ioctl that enables adding fds Sargun Dhillon
2020-05-24 23:39 ` [PATCH 1/5] seccomp: Add find_notification helper Sargun Dhillon
2020-05-24 23:55   ` Tycho Andersen
2020-05-25 13:26   ` Christian Brauner
2020-05-24 23:39 ` [PATCH 2/5] seccomp: Introduce addfd ioctl to seccomp user notifier Sargun Dhillon
2020-05-24 23:57   ` Tycho Andersen
2020-05-24 23:58     ` Tycho Andersen
2020-05-25  0:05   ` Al Viro [this message]
2020-05-25  0:27     ` Sargun Dhillon
2020-05-25  0:39       ` Al Viro
2020-05-25 13:50   ` Christian Brauner
2020-05-26  6:59     ` Sargun Dhillon
2020-05-26  8:22       ` Christian Brauner
2020-05-24 23:39 ` [PATCH 3/5] selftests/seccomp: Test SECCOMP_IOCTL_NOTIF_ADDFD Sargun Dhillon
2020-05-24 23:39 ` [PATCH 4/5] seccomp: Add SECCOMP_ADDFD_FLAG_MOVE flag to add fd ioctl Sargun Dhillon
2020-05-25 14:20   ` Christian Brauner
2020-05-26  6:08     ` Sargun Dhillon
2020-05-24 23:39 ` [PATCH 5/5] selftests/seccomp: Add test for addfd move semantics Sargun Dhillon

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