apparmor: Fix change_onexec when called from a confined task

Fix failure in aa_change_onexec api when the request is made from a confined
task.  This failure was caused by two problems

 The AA_MAY_ONEXEC perm was not being mapped correctly for this case.

 The executable name was being checked as second time instead of using the
 requested onexec profile name, which may not be the same as the exec
 profile name. This mistake can not be exploited to grant extra permission
 because of the above flaw where the ONEXEC permission was not being mapped
 so it will not be granted.

BugLink: http://bugs.launchpad.net/bugs/963756

Signed-off-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>

security/apparmor/domain.c

@@ -410,7 +410,8 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
 		 * exec\0change_profile
 		 */
 		state = aa_dfa_null_transition(profile->file.dfa, state);
-		cp = change_profile_perms(profile, cxt->onexec->ns, name,
+		cp = change_profile_perms(profile, cxt->onexec->ns,
+					  cxt->onexec->base.name,
 					  AA_MAY_ONEXEC, state);
 
 		if (!(cp.allow & AA_MAY_ONEXEC))

security/apparmor/file.c

@@ -215,6 +215,8 @@ static struct file_perms compute_perms(struct aa_dfa *dfa, unsigned int state,
 	/* change_profile wasn't determined by ownership in old mapping */
 	if (ACCEPT_TABLE(dfa)[state] & 0x80000000)
 		perms.allow |= AA_MAY_CHANGE_PROFILE;
+	if (ACCEPT_TABLE(dfa)[state] & 0x40000000)
+		perms.allow |= AA_MAY_ONEXEC;
 
 	return perms;
 }