linux-kernel - Re: [PATCH -next] cred: conditionally declare groups-related functions

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Date:   Thu, 21 Jun 2018 17:17:24 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     omosnace@...hat.com
Cc:     akpm@...ux-foundation.org, rdunlap@...radead.org,
        sfr@...b.auug.org.au, Eric Paris <eparis@...hat.com>,
        linux-kernel@...r.kernel.org, linux-next@...r.kernel.org,
        linux-audit@...hat.com
Subject: Re: [PATCH -next] cred: conditionally declare groups-related functions

On Thu, Jun 21, 2018 at 4:33 AM Ondrej Mosnacek <omosnace@...hat.com> wrote:
>
> The groups-related functions declared in include/linux/cred.h are
> defined in kernel/groups.c, which is compiled only when
> CONFIG_MULTIUSER=y. Move all these function declarations under #ifdef
> CONFIG_MULTIUSER to help avoid accidental usage in contexts where
> CONFIG_MULTIUSER might be disabled.
>
> This patch also adds a fallback for groups_search(). Currently this
> function is only called from kernel/groups.c itself and
> keys/permissions.c, which depends on CONFIG_MULTIUSER. However, the
> audit subsystem (which does not depend on CONFIG_MULTIUSER) calls this
> function in -next, so the fallback will be needed to avoid compilation
> errors or ugly workarounds.
>
> See also:
> https://lkml.org/lkml/2018/6/20/670
> https://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/audit.git/commit/?h=next&id=af85d1772e31fed34165a1b3decef340cf4080c0
>
> Reported-by: Randy Dunlap <rdunlap@...radead.org>
> Signed-off-by: Ondrej Mosnacek <omosnace@...hat.com>
> ---
>  include/linux/cred.h | 16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/cred.h b/include/linux/cred.h
> index 631286535d0f..8917768453cc 100644
> --- a/include/linux/cred.h
> +++ b/include/linux/cred.h
> @@ -65,6 +65,12 @@ extern void groups_free(struct group_info *);
>
>  extern int in_group_p(kgid_t);
>  extern int in_egroup_p(kgid_t);
> +
> +extern int set_current_groups(struct group_info *);
> +extern void set_groups(struct cred *, struct group_info *);
> +extern int groups_search(const struct group_info *, kgid_t);
> +extern bool may_setgroups(void);
> +extern void groups_sort(struct group_info *);
>  #else
>  static inline void groups_free(struct group_info *group_info)
>  {
> @@ -78,12 +84,12 @@ static inline int in_egroup_p(kgid_t grp)
>  {
>          return 1;
>  }
> +
> +static inline int groups_search(const struct group_info *group_info, kgid_t grp)
> +{
> +       return 0;

Is this the right fallback value?  If CONFIG_MULTIUSER is disabled,
wouldn't we always want to indicate a group match?  The in_group_p()
and in_egroup_p() dummy functions would seem to indicate that is the
correct behavior ...

> +}
>  #endif
> -extern int set_current_groups(struct group_info *);
> -extern void set_groups(struct cred *, struct group_info *);
> -extern int groups_search(const struct group_info *, kgid_t);
> -extern bool may_setgroups(void);
> -extern void groups_sort(struct group_info *);
>
>  /*
>   * The security context of a task
> --
> 2.17.1
>


-- 
paul moore
www.paul-moore.com