From: Christian Brauner <christian.brauner@ubuntu.com>
To: Sargun Dhillon <sargun@sargun.me>
Cc: linux-kernel@vger.kernel.org,
containers@lists.linux-foundation.org, linux-api@vger.kernel.org,
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 4/5] seccomp: Add SECCOMP_ADDFD_FLAG_MOVE flag to add fd ioctl
Date: Mon, 25 May 2020 16:20:43 +0200 [thread overview]
Message-ID: <20200525142043.jkdsfabntqusizxz@wittgenstein> (raw)
In-Reply-To: <20200524233942.8702-5-sargun@sargun.me>
On Sun, May 24, 2020 at 04:39:41PM -0700, Sargun Dhillon wrote:
> Certain files, when moved to another process have metadata changed, such
> as netprioidx, and classid. This is the default behaviour in sending
> sockets with SCM_RIGHTS over unix sockets. Depending on the usecase,
> this may or may not be desirable with the addfd ioctl. This allows
> the user to opt-in.
>
> Signed-off-by: Sargun Dhillon <sargun@sargun.me>
> Suggested-by: Tycho Andersen <tycho@tycho.ws>
> Cc: Matt Denton <mpdenton@google.com>
> Cc: Kees Cook <keescook@google.com>,
> Cc: Jann Horn <jannh@google.com>,
> Cc: Robert Sesek <rsesek@google.com>,
> Cc: Chris Palmer <palmer@google.com>
> Cc: Christian Brauner <christian.brauner@ubuntu.com>
> ---
> include/uapi/linux/seccomp.h | 8 ++++++++
> kernel/seccomp.c | 31 +++++++++++++++++++++++++++----
> 2 files changed, 35 insertions(+), 4 deletions(-)
>
> diff --git a/include/uapi/linux/seccomp.h b/include/uapi/linux/seccomp.h
> index 7d450a9e4c29..ccd1c960372a 100644
> --- a/include/uapi/linux/seccomp.h
> +++ b/include/uapi/linux/seccomp.h
> @@ -115,6 +115,14 @@ struct seccomp_notif_resp {
>
> /* valid flags for seccomp_notif_addfd */
> #define SECCOMP_ADDFD_FLAG_SETFD (1UL << 0) /* Specify remote fd */
> +/*
> + * Certain file descriptors are behave differently depending on the process
"do behave"?
> + * they are created in. Specifcally, sockets, and their interactions with the
> + * net_cls and net_prio cgroup v1 controllers. This "moves" the file descriptor
> + * so that it takes on the cgroup controller's configuration in the process
> + * that the file descriptor is being added to.
> + */
> +#define SECCOMP_ADDFD_FLAG_MOVE (1UL << 1)
I'm not happy about the name because "moving" has much more to do with
transferring ownership than what we are doing here. After a "move" the
fd shouldn't be valid anymore. But that might just be my thinking.
But why make this opt-in and not do it exactly like when you send around
fds and make this mandatory?
next prev parent reply other threads:[~2020-05-25 14:20 UTC|newest]
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
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 [this message]
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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