linux-kernel - Re: [PATCH v2 08/11] ipv4: reorder capability check last

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Message-ID: <CANn89iLDDfWJqtxnC463t5aM_p4-4iUjVNfvuxZs=_DXeThGww@mail.gmail.com>
Date: Sun, 2 Mar 2025 19:24:00 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: cgzones@...glemail.com
Cc: Serge Hallyn <serge@...lyn.com>, Jan Kara <jack@...e.com>, 
	Julia Lawall <Julia.Lawall@...ia.fr>, Nicolas Palix <nicolas.palix@...g.fr>, 
	linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org, 
	cocci@...ia.fr, Neal Cardwell <ncardwell@...gle.com>, 
	Kuniyuki Iwashima <kuniyu@...zon.com>, "David S. Miller" <davem@...emloft.net>, 
	David Ahern <dsahern@...nel.org>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Simon Horman <horms@...nel.org>, netdev@...r.kernel.org
Subject: Re: [PATCH v2 08/11] ipv4: reorder capability check last

On Sun, Mar 2, 2025 at 5:07 PM Christian Göttsche
<cgoettsche@...tendoof.de> wrote:
>
> From: Christian Göttsche <cgzones@...glemail.com>
>
> capable() calls refer to enabled LSMs whether to permit or deny the
> request.  This is relevant in connection with SELinux, where a
> capability check results in a policy decision and by default a denial
> message on insufficient permission is issued.
> It can lead to three undesired cases:
>   1. A denial message is generated, even in case the operation was an
>      unprivileged one and thus the syscall succeeded, creating noise.
>   2. To avoid the noise from 1. the policy writer adds a rule to ignore
>      those denial messages, hiding future syscalls, where the task
>      performs an actual privileged operation, leading to hidden limited
>      functionality of that task.
>   3. To avoid the noise from 1. the policy writer adds a rule to permit
>      the task the requested capability, while it does not need it,
>      violating the principle of least privilege.
>
> Signed-off-by: Christian Göttsche <cgzones@...glemail.com>
> Reviewed-by: Serge Hallyn <serge@...lyn.com>

Reviewed-by: Eric Dumazet <edumazet@...gle.com>