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

[Richard Guy Briggs]

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 at 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;
 }
 
+#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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