exec: Consolidate dumpability logic

Since it's already valid to set dumpability in the early part of
setup_new_exec(), we can consolidate the logic into a single place.
The BINPRM_FLAGS_ENFORCE_NONDUMP is set during would_dump() calls
before setup_new_exec(), so its test is safe to move as well.
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Serge Hallyn <serge@hallyn.com>
Reviewed-by: James Morris <james.l.morris@oracle.com>

fs/exec.c

@@ -1354,10 +1354,12 @@ void setup_new_exec(struct linux_binprm * bprm)
 
 	current->sas_ss_sp = current->sas_ss_size = 0;
 
-	if (!bprm->secureexec)
-		set_dumpable(current->mm, SUID_DUMP_USER);
-	else
+	/* Figure out dumpability. */
+	if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP ||
+	    bprm->secureexec)
 		set_dumpable(current->mm, suid_dumpable);
+	else
+		set_dumpable(current->mm, SUID_DUMP_USER);
 
 	arch_setup_new_exec();
 	perf_event_exec();
@@ -1371,9 +1373,6 @@ void setup_new_exec(struct linux_binprm * bprm)
 
 	if (bprm->secureexec) {
 		current->pdeath_signal = 0;
-	} else {
-		if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)
-			set_dumpable(current->mm, suid_dumpable);
 	}
 
 	/* An exec changes our domain. We are no longer part of the thread