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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAHC9VhSgbHx4NcMVjMMk0D332b0DTEQi6dD_wO1fvQne-JVisw@mail.gmail.com>
Date: Mon, 26 Jan 2026 17:52:03 -0500
From: Paul Moore <paul@...l-moore.com>
To: Ondrej Mosnacek <omosnace@...hat.com>
Cc: 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 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>

-- 
paul-moore.com