linux-kernel - Re: [PATCH 3/3] capabilities: add cap userns sysctl mask

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Date: Mon, 20 May 2024 12:25:27 -0700
From: Jonathan Calmels <jcalmels@...0.net>
To: Tycho Andersen <tycho@...ho.pizza>
Cc: brauner@...nel.org, ebiederm@...ssion.com, 
	Luis Chamberlain <mcgrof@...nel.org>, Kees Cook <keescook@...omium.org>, 
	Joel Granados <j.granados@...sung.com>, Serge Hallyn <serge@...lyn.com>, 
	Paul Moore <paul@...l-moore.com>, James Morris <jmorris@...ei.org>, 
	David Howells <dhowells@...hat.com>, Jarkko Sakkinen <jarkko@...nel.org>, containers@...ts.linux.dev, 
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org, 
	linux-security-module@...r.kernel.org, keyrings@...r.kernel.org
Subject: Re: [PATCH 3/3] capabilities: add cap userns sysctl mask

On Mon, May 20, 2024 at 07:30:14AM GMT, Tycho Andersen wrote:
> there is an ongoing effort (started at [0]) to constify the first arg
> here, since you're not supposed to write to it. Your usage looks
> correct to me, so I think all it needs is a literal "const" here.

Will do, along with the suggestions from Jarkko

> > +	struct ctl_table t;
> > +	unsigned long mask_array[2];
> > +	kernel_cap_t new_mask, *mask;
> > +	int err;
> > +
> > +	if (write && (!capable(CAP_SETPCAP) ||
> > +		      !capable(CAP_SYS_ADMIN)))
> > +		return -EPERM;
> 
> ...why CAP_SYS_ADMIN? You mention it in the changelog, but don't
> explain why.

No reason really, I was hoping we could decide what we want here.
UMH uses CAP_SYS_MODULE, Serge mentioned adding a new cap maybe.