[PATCH V3 05/10] capabilities: use intuitive names for id changes

[Richard Guy Briggs]

Introduce a number of inlines to make the use of the negation of
uid_eq() easier to read and analyse.

Signed-off-by: Richard Guy Briggs <rgb at redhat.com>
---
 security/commoncap.c |   26 +++++++++++++++++++++-----
 1 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/security/commoncap.c b/security/commoncap.c
index 36c38a1..1af7dec 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -483,6 +483,15 @@ static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_f
 
 static inline bool root_privileged(void) { return !issecure(SECURE_NOROOT); }
 
+static inline bool is_real(kuid_t uid, struct cred *cred)
+{ return uid_eq(cred->uid, uid); }
+
+static inline bool is_eff(kuid_t uid, struct cred *cred)
+{ return uid_eq(cred->euid, uid); }
+
+static inline bool is_suid(kuid_t uid, struct cred *cred)
+{ return !is_real(uid, cred) && is_eff(uid, cred); }
+
 void handle_privileged_root(struct linux_binprm *bprm, bool has_fcap, bool *effective, kuid_t root_uid)
 {
 	const struct cred *old = current_cred();
@@ -493,7 +502,7 @@ void handle_privileged_root(struct linux_binprm *bprm, bool has_fcap, bool *effe
 	 * for a setuid root binary run by a non-root user.  Do set it
 	 * for a root user just to cause least surprise to an admin.
 	 */
-	if (has_fcap && !uid_eq(new->uid, root_uid) && uid_eq(new->euid, root_uid)) {
+	if (has_fcap && is_suid(root_uid, new)) {
 		warn_setuid_and_fcaps_mixed(bprm->filename);
 		return;
 	}
@@ -504,12 +513,12 @@ void handle_privileged_root(struct linux_binprm *bprm, bool has_fcap, bool *effe
 	 *
 	 * If only the real uid is 0, we do not set the effective bit.
 	 */
-	if (uid_eq(new->euid, root_uid) || uid_eq(new->uid, root_uid)) {
+	if (is_eff(root_uid, new) || is_real(root_uid, new)) {
 		/* pP' = (cap_bset & ~0) | (pI & ~0) */
 		new->cap_permitted = cap_combine(old->cap_bset,
 						 old->cap_inheritable);
 	}
-	if (uid_eq(new->euid, root_uid))
+	if (is_eff(root_uid, new))
 		*effective = true;
 }
 
@@ -519,6 +528,13 @@ void handle_privileged_root(struct linux_binprm *bprm, bool has_fcap, bool *effe
 	!cap_issubset(cred->cap_##target, cred->cap_##source)
 #define cap_full(field, cred) \
 	cap_issubset(CAP_FULL_SET, cred->cap_##field)
+
+static inline bool is_setuid(struct cred *new, const struct cred *old)
+{ return !uid_eq(new->euid, old->uid); }
+
+static inline bool is_setgid(struct cred *new, const struct cred *old)
+{ return !gid_eq(new->egid, old->gid); }
+
 /**
  * cap_bprm_set_creds - Set up the proposed credentials for execve().
  * @bprm: The execution parameters, including the proposed creds
@@ -556,7 +572,7 @@ int cap_bprm_set_creds(struct linux_binprm *bprm)
 	 *
 	 * In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
 	 */
-	is_setid = !uid_eq(new->euid, old->uid) || !gid_eq(new->egid, old->gid);
+	is_setid = is_setuid(new, old) || is_setgid(new, old);
 
 	if ((is_setid || cap_gained(permitted, new, old)) &&
 	    ((bprm->unsafe & ~LSM_UNSAFE_PTRACE) ||
@@ -612,7 +628,7 @@ int cap_bprm_set_creds(struct linux_binprm *bprm)
 	 */
 	if (cap_grew(effective, ambient, new)) {
 		if (!cap_full(effective, new) ||
-		    !uid_eq(new->euid, root_uid) || !uid_eq(new->uid, root_uid) ||
+		    !is_eff(root_uid, new) || !is_real(root_uid, new) ||
 		    !root_privileged()) {
 			ret = audit_log_bprm_fcaps(bprm, new, old);
 			if (ret < 0)
-- 
1.7.1

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