1 files changed, 128 insertions, 65 deletions

diff --git a/security/commoncap.c b/security/commoncap.c
index fc46f5b85251..4f8e09340956 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -536,7 +536,7 @@ int cap_convert_nscap(struct dentry *dentry, void **ivalue, size_t size)
 static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
 					  struct linux_binprm *bprm,
 					  bool *effective,
-					  bool *has_cap)
+					  bool *has_fcap)
 {
 	struct cred *new = bprm->cred;
 	unsigned i;
@@ -546,7 +546,7 @@ static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
 		*effective = true;
 
 	if (caps->magic_etc & VFS_CAP_REVISION_MASK)
-		*has_cap = true;
+		*has_fcap = true;
 
 	CAP_FOR_EACH_U32(i) {
 		__u32 permitted = caps->permitted.cap[i];
@@ -653,7 +653,7 @@ int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data
  * its xattrs and, if present, apply them to the proposed credentials being
  * constructed by execve().
  */
-static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_cap)
+static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_fcap)
 {
 	int rc = 0;
 	struct cpu_vfs_cap_data vcaps;
@@ -684,7 +684,7 @@ static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_c
 		goto out;
 	}
 
-	rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_cap);
+	rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_fcap);
 	if (rc == -EINVAL)
 		printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n",
 		       __func__, rc, bprm->filename);
@@ -696,6 +696,115 @@ out:
 	return rc;
 }
 
+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); }
+
+/*
+ * handle_privileged_root - Handle case of privileged root
+ * @bprm: The execution parameters, including the proposed creds
+ * @has_fcap: Are any file capabilities set?
+ * @effective: Do we have effective root privilege?
+ * @root_uid: This namespace' root UID WRT initial USER namespace
+ *
+ * Handle the case where root is privileged and hasn't been neutered by
+ * SECURE_NOROOT.  If file capabilities are set, they won't be combined with
+ * set UID root and nothing is changed.  If we are root, cap_permitted is
+ * updated.  If we have become set UID root, the effective bit is set.
+ */
+static void handle_privileged_root(struct linux_binprm *bprm, bool has_fcap,
+				   bool *effective, kuid_t root_uid)
+{
+	const struct cred *old = current_cred();
+	struct cred *new = bprm->cred;
+
+	if (!root_privileged())
+		return;
+	/*
+	 * If the legacy file capability is set, then don't set privs
+	 * 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 && __is_suid(root_uid, new)) {
+		warn_setuid_and_fcaps_mixed(bprm->filename);
+		return;
+	}
+	/*
+	 * To support inheritance of root-permissions and suid-root
+	 * executables under compatibility mode, we override the
+	 * capability sets for the file.
+	 */
+	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 only the real uid is 0, we do not set the effective bit.
+	 */
+	if (__is_eff(root_uid, new))
+		*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)
+
+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); }
+
+/*
+ * 1) Audit candidate if current->cap_effective is set
+ *
+ * We do not bother to audit if 3 things are true:
+ *   1) cap_effective has all caps
+ *   2) we became root *OR* are were already root
+ *   3) root is supposed to have all caps (SECURE_NOROOT)
+ * Since this is just a normal root execing a process.
+ *
+ * Number 1 above might fail if you don't have a full bset, but I think
+ * that is interesting information to audit.
+ *
+ * A number of other conditions require logging:
+ * 2) something prevented setuid root getting all caps
+ * 3) non-setuid root gets fcaps
+ * 4) non-setuid root gets ambient
+ */
+static inline bool nonroot_raised_pE(struct cred *new, const struct cred *old,
+				     kuid_t root, bool has_fcap)
+{
+	bool ret = false;
+
+	if ((__cap_grew(effective, ambient, new) &&
+	     !(__cap_full(effective, new) &&
+	       (__is_eff(root, new) || __is_real(root, new)) &&
+	       root_privileged())) ||
+	    (root_privileged() &&
+	     __is_suid(root, new) &&
+	     !__cap_full(effective, new)) ||
+	    (!__is_setuid(new, old) &&
+	     ((has_fcap &&
+	       __cap_gained(permitted, new, old)) ||
+	      __cap_gained(ambient, new, old))))
+
+		ret = true;
+
+	return ret;
+}
+
 /**
  * cap_bprm_set_creds - Set up the proposed credentials for execve().
  * @bprm: The execution parameters, including the proposed creds
@@ -708,61 +817,33 @@ int cap_bprm_set_creds(struct linux_binprm *bprm)
 {
 	const struct cred *old = current_cred();
 	struct cred *new = bprm->cred;
-	bool effective, has_cap = false, is_setid;
+	bool effective = false, has_fcap = false, is_setid;
 	int ret;
 	kuid_t root_uid;
 
 	if (WARN_ON(!cap_ambient_invariant_ok(old)))
 		return -EPERM;
 
-	effective = false;
-	ret = get_file_caps(bprm, &effective, &has_cap);
+	ret = get_file_caps(bprm, &effective, &has_fcap);
 	if (ret < 0)
 		return ret;
 
 	root_uid = make_kuid(new->user_ns, 0);
 
-	if (!issecure(SECURE_NOROOT)) {
-		/*
-		 * If the legacy file capability is set, then don't set privs
-		 * 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_cap && !uid_eq(new->uid, root_uid) && uid_eq(new->euid, root_uid)) {
-			warn_setuid_and_fcaps_mixed(bprm->filename);
-			goto skip;
-		}
-		/*
-		 * To support inheritance of root-permissions and suid-root
-		 * executables under compatibility mode, we override the
-		 * capability sets for the file.
-		 *
-		 * 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)) {
-			/* pP' = (cap_bset & ~0) | (pI & ~0) */
-			new->cap_permitted = cap_combine(old->cap_bset,
-							 old->cap_inheritable);
-		}
-		if (uid_eq(new->euid, root_uid))
-			effective = true;
-	}
-skip:
+	handle_privileged_root(bprm, has_fcap, &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.
 	 *
 	 * 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_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 */
@@ -779,7 +860,7 @@ skip:
 	new->sgid = new->fsgid = new->egid;
 
 	/* File caps or setid cancels ambient. */
-	if (has_cap || is_setid)
+	if (has_fcap || is_setid)
 		cap_clear(new->cap_ambient);
 
 	/*
@@ -800,26 +881,10 @@ skip:
 	if (WARN_ON(!cap_ambient_invariant_ok(new)))
 		return -EPERM;
 
-	/*
-	 * Audit candidate if current->cap_effective is set
-	 *
-	 * We do not bother to audit if 3 things are true:
-	 *   1) cap_effective has all caps
-	 *   2) we are root
-	 *   3) root is supposed to have all caps (SECURE_NOROOT)
-	 * Since this is just a normal root execing a process.
-	 *
-	 * 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) ||
-		    !uid_eq(new->euid, root_uid) || !uid_eq(new->uid, root_uid) ||
-		    issecure(SECURE_NOROOT)) {
-			ret = audit_log_bprm_fcaps(bprm, new, old);
-			if (ret < 0)
-				return ret;
-		}
+	if (nonroot_raised_pE(new, old, root_uid, has_fcap)) {
+		ret = audit_log_bprm_fcaps(bprm, new, old);
+		if (ret < 0)
+			return ret;
 	}
 
 	new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
@@ -829,13 +894,11 @@ skip:
 
 	/* Check for privilege-elevated exec. */
 	bprm->cap_elevated = 0;
-	if (is_setid) {
+	if (is_setid ||
+	    (!__is_real(root_uid, new) &&
+	     (effective ||
+	      __cap_grew(permitted, ambient, new))))
 		bprm->cap_elevated = 1;
-	} else if (!uid_eq(new->uid, root_uid)) {
-		if (effective ||
-		    !cap_issubset(new->cap_permitted, new->cap_ambient))
-			bprm->cap_elevated = 1;
-	}
 
 	return 0;
 }