[PATCH 06/10] LSM: SafeSetID: fix userns handling in securityfs

[Kees Cook]

On Wed, Apr 10, 2019 at 9:56 AM Micah Morton <mortonm at chromium.org> wrote:
>
> From: Jann Horn <jannh at google.com>
>
> Looking at current_cred() in write handlers is bad form, stop doing that.
>
> Also, let's just require that the write is coming from the initial user
> namespace. Especially SAFESETID_WHITELIST_FLUSH requires privilege over all
> namespaces, and SAFESETID_WHITELIST_ADD should probably require it as well.
>
> Signed-off-by: Jann Horn <jannh at google.com>
> Signed-off-by: Micah Morton <mortonm at chromium.org>

Reviewed-by: Kees Cook <keescook at chromium.org>

-Kees

> ---
>  security/safesetid/securityfs.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/security/safesetid/securityfs.c b/security/safesetid/securityfs.c
> index 87e42b7f3e33..76c1e8a6ab93 100644
> --- a/security/safesetid/securityfs.c
> +++ b/security/safesetid/securityfs.c
> @@ -59,8 +59,8 @@ static int parse_policy_line(
>         if (ret)
>                 return ret;
>
> -       *parent = make_kuid(current_user_ns(), parsed_parent);
> -       *child = make_kuid(current_user_ns(), parsed_child);
> +       *parent = make_kuid(file->f_cred->user_ns, parsed_parent);
> +       *child = make_kuid(file->f_cred->user_ns, parsed_child);
>         if (!uid_valid(*parent) || !uid_valid(*child))
>                 return -EINVAL;
>
> @@ -92,7 +92,7 @@ static ssize_t safesetid_file_write(struct file *file,
>         kuid_t child;
>         int ret;
>
> -       if (!ns_capable(current_user_ns(), CAP_MAC_ADMIN))
> +       if (!file_ns_capable(file, &init_user_ns, CAP_MAC_ADMIN))
>                 return -EPERM;
>
>         if (*ppos != 0)
> --
> 2.21.0.392.gf8f6787159e-goog
>


-- 
Kees Cook