linux-kernel - Re: [PATCH v1 1/3] landlock: Log the TGID of the domain creator

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Message-ID: <20250411.3c94c5c9e6bb@gnoack.org>
Date: Fri, 11 Apr 2025 10:35:31 +0200
From: Günther Noack <gnoack3000@...il.com>
To: Mickaël Salaün <mic@...ikod.net>
Cc: Günther Noack <gnoack@...gle.com>,
	linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org,
	Christian Brauner <brauner@...nel.org>,
	Paul Moore <paul@...l-moore.com>
Subject: Re: [PATCH v1 1/3] landlock: Log the TGID of the domain creator

On Thu, Apr 10, 2025 at 07:17:21PM +0200, Mickaël Salaün wrote:
> As for other Audit's "pid" fields, Landlock should use the task's TGID
> instead of its TID.  Fix this issue by keeping a reference to the TGID
> of the domain creator.
> 
> Existing tests already check for the PID but only with the thread group
> leader, so always the TGID.  A following patch adds dedicated tests for
> non-leader thread.
> 
> Remove the current_real_cred() check which does not make sense because
> we only reference a struct pid, whereas a previous version did reference
> a struct cred instead.
> 
> Cc: Christian Brauner <brauner@...nel.org>
> Cc: Günther Noack <gnoack@...gle.com>
> Cc: Paul Moore <paul@...l-moore.com>
> Signed-off-by: Mickaël Salaün <mic@...ikod.net>
> ---
>  security/landlock/domain.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/security/landlock/domain.c b/security/landlock/domain.c
> index bae2e9909013..a647b68e8d06 100644
> --- a/security/landlock/domain.c
> +++ b/security/landlock/domain.c
> @@ -16,6 +16,7 @@
>  #include <linux/path.h>
>  #include <linux/pid.h>
>  #include <linux/sched.h>
> +#include <linux/signal.h>
>  #include <linux/uidgid.h>
>  
>  #include "access.h"
> @@ -99,8 +100,7 @@ static struct landlock_details *get_current_details(void)
>  		return ERR_PTR(-ENOMEM);
>  
>  	memcpy(details->exe_path, path_str, path_size);
> -	WARN_ON_ONCE(current_cred() != current_real_cred());
> -	details->pid = get_pid(task_pid(current));
> +	details->pid = get_pid(task_tgid(current));
>  	details->uid = from_kuid(&init_user_ns, current_uid());
>  	get_task_comm(details->comm, current);
>  	return details;
> -- 
> 2.49.0
> 

Ah, a classic! Good catch finding this early enough for 6.15!

Reviewed-by: Günther Noack <gnoack3000@...il.com>