linux-kernel - Re: [PATCH] ucount: check for CAP_SYS_RESOURCE using ns_capable

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Message-ID: <aXgZI1td0Hremulj@mail.hallyn.com>
Date: Mon, 26 Jan 2026 19:47:15 -0600
From: "Serge E. Hallyn" <serge@...lyn.com>
To: Paul Moore <paul@...l-moore.com>
Cc: Ondrej Mosnacek <omosnace@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Eric W . Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org,
	selinux@...r.kernel.org
Subject: Re: [PATCH] ucount: check for CAP_SYS_RESOURCE using
 ns_capable_noaudit()

On Mon, Jan 26, 2026 at 05:52:03PM -0500, Paul Moore wrote:
> On Thu, Jan 22, 2026 at 9:25 AM Ondrej Mosnacek <omosnace@...hat.com> wrote:
> >
> > The user.* sysctls implement the ctl_table_root::permissions hook and
> > they override the file access mode based on the CAP_SYS_RESOURCE
> > capability (at most rwx if capable, at most r-- if not). The capability
> > is being checked unconditionally, so if an LSM denies the capability, an
> > audit record may be logged even when access is in fact granted.
> >
> > Given the logic in the set_permissions() function in kernel/ucount.c and
> > the unfortunate way the permission checking is implemented, it doesn't
> > seem viable to avoid false positive denials by deferring the capability
> > check. Thus, do the same as in net_ctl_permissions() (net/sysctl_net.c)
> > - switch from ns_capable() to ns_capable_noaudit(), so that the check
> > never logs an audit record.
> >
> > Fixes: dbec28460a89 ("userns: Add per user namespace sysctls.")
> > Signed-off-by: Ondrej Mosnacek <omosnace@...hat.com>
> > ---
> >  kernel/ucount.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Reviewed-by: Paul Moore <paul@...l-moore.com>

Acked-by: Serge Hallyn <serge@...lyn.com>

Looks good to me.  What tree should this go through?  Network?