[PATCH V3 02/10] capabilities: intuitive names for cap gain status

[serge@hallyn.com (Serge E. Hallyn)]

Quoting Richard Guy Briggs (rgb at redhat.com):
> Introduce macros cap_gained, cap_grew, cap_full to make the use of the
> negation of is_subset() easier to read and analyse.
> 
> Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
> ---
>  security/commoncap.c |   16 ++++++++++------
>  1 files changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/security/commoncap.c b/security/commoncap.c
> index b7fbf77..6f05ec0 100644
> --- a/security/commoncap.c
> +++ b/security/commoncap.c
> @@ -513,6 +513,12 @@ void handle_privileged_root(struct linux_binprm *bprm, bool has_cap, bool *effec
>  		*effective = true;
>  }
>  

It's subjective and so might be just me, but I think I'd find it easier
to read if it was cap_gained(source, target, field) and cap_grew(cred, source, target)

This looks correct though, so either way

Reviewed-by: Serge Hallyn <serge@hallyn.com>

> +#define cap_gained(field, target, source) \
> +	!cap_issubset(target->cap_##field, source->cap_##field)
> +#define cap_grew(target, source, cred) \
> +	!cap_issubset(cred->cap_##target, cred->cap_##source)
> +#define cap_full(field, cred) \
> +	cap_issubset(CAP_FULL_SET, cred->cap_##field)
>  /**
>   * cap_bprm_set_creds - Set up the proposed credentials for execve().
>   * @bprm: The execution parameters, including the proposed creds
> @@ -541,10 +547,9 @@ int cap_bprm_set_creds(struct linux_binprm *bprm)
>  	handle_privileged_root(bprm, has_cap, &effective, root_uid);
>  
>  	/* if we have fs caps, clear dangerous personality flags */
> -	if (!cap_issubset(new->cap_permitted, old->cap_permitted))
> +	if (cap_gained(permitted, new, old))
>  		bprm->per_clear |= PER_CLEAR_ON_SETID;
>  
> -
>  	/* Don't let someone trace a set[ug]id/setpcap binary with the revised
>  	 * credentials unless they have the appropriate permit.
>  	 *
> @@ -552,8 +557,7 @@ int cap_bprm_set_creds(struct linux_binprm *bprm)
>  	 */
>  	is_setid = !uid_eq(new->euid, old->uid) || !gid_eq(new->egid, old->gid);
>  
> -	if ((is_setid ||
> -	     !cap_issubset(new->cap_permitted, old->cap_permitted)) &&
> +	if ((is_setid || cap_gained(permitted, new, old)) &&
>  	    ((bprm->unsafe & ~LSM_UNSAFE_PTRACE) ||
>  	     !ptracer_capable(current, new->user_ns))) {
>  		/* downgrade; they get no more than they had, and maybe less */
> @@ -605,8 +609,8 @@ int cap_bprm_set_creds(struct linux_binprm *bprm)
>  	 * Number 1 above might fail if you don't have a full bset, but I think
>  	 * that is interesting information to audit.
>  	 */
> -	if (!cap_issubset(new->cap_effective, new->cap_ambient)) {
> -		if (!cap_issubset(CAP_FULL_SET, new->cap_effective) ||
> +	if (cap_grew(effective, ambient, new)) {
> +		if (!cap_full(effective, new) ||
>  		    !uid_eq(new->euid, root_uid) || !uid_eq(new->uid, root_uid) ||
>  		    issecure(SECURE_NOROOT)) {
>  			ret = audit_log_bprm_fcaps(bprm, new, old);
> -- 
> 1.7.1
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