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capabilities: intuitive names for cap gain status 

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>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Acked-by: James Morris <james.l.morris@oracle.com>
Acked-by: Kees Cook <keescook@chromium.org>
Okay-ished-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>
This commit is contained in:
Richard Guy Briggs 2017-10-11 20:57:06 -04:00 committed by James Morris
parent db1a8922cf
commit 4c7e715fc8
1 changed files with 11 additions and 7 deletions
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18
security/commoncap.c
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@ -741,6 +741,12 @@ static void handle_privileged_root(struct linux_binprm *bprm, bool has_cap,
*effective = true;
}
#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
@ -769,10 +775,9 @@ 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.
*
@ -780,8 +785,7 @@ 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 */
@ -831,8 +835,8 @@ 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);
@ -852,7 +856,7 @@ int cap_bprm_set_creds(struct linux_binprm *bprm)
bprm->cap_elevated = 1;
} else if (!uid_eq(new->uid, root_uid)) {
if (effective ||
!cap_issubset(new->cap_permitted, new->cap_ambient))
__cap_grew(permitted, ambient, new))
bprm->cap_elevated = 1;
}