linux-kernel - Re: [PATCH v1 1/2] Landlock: Add signal control

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Message-ID: <CAG48ez3MNJ9QiULabERc-SWQLx4T80_UOvsqCVFXTi3yxeeMRg@mail.gmail.com>
Date: Mon, 22 Jul 2024 14:45:35 +0200
From: Jann Horn <jannh@...gle.com>
To: Tahera Fahimi <fahimitahera@...il.com>
Cc: mic@...ikod.net, gnoack@...gle.com, paul@...l-moore.com, jmorris@...ei.org, 
	serge@...lyn.com, linux-security-module@...r.kernel.org, 
	linux-kernel@...r.kernel.org, bjorn3_gh@...tonmail.com, 
	outreachy@...ts.linux.dev, netdev@...r.kernel.org
Subject: Re: [PATCH v1 1/2] Landlock: Add signal control

On Fri, Jul 5, 2024 at 11:22 PM Tahera Fahimi <fahimitahera@...il.com> wrote:
> Currently, a sandbox process is not restricted to send a signal
> (e.g. SIGKILL) to a process outside of the sandbox environment.
> Ability to sending a signal for a sandboxed process should be
> scoped the same way abstract unix sockets are scoped.
>
> The same way as abstract unix socket, we extend "scoped" field
> in a ruleset with "LANDLOCK_SCOPED_SIGNAL" to specify that a ruleset
> will deny sending any signal from within a sandbox process to its
> parent(i.e. any parent sandbox or non-sandboxed procsses).
>
> Signed-off-by: Tahera Fahimi <fahimitahera@...il.com>
[...]
> +static int hook_file_send_sigiotask(struct task_struct *tsk,
> +                                   struct fown_struct *fown, int signum)
> +{
> +       const struct task_struct *result =
> +               get_pid_task(fown->pid, fown->pid_type);

get_pid_task() returns a refcounted reference; you'll have to call
put_task_struct(result) to drop this reference at the end of the
function.

> +       const struct landlock_ruleset *const dom =
> +               landlock_get_task_domain(result);
> +       if (signal_is_scoped(dom, tsk))
> +               return 0;
> +       return EPERM;
> +}