Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964908AbcDLQoc (ORCPT ); Tue, 12 Apr 2016 12:44:32 -0400 Received: from mail-pf0-f171.google.com ([209.85.192.171]:33877 "EHLO mail-pf0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756200AbcDLQob (ORCPT ); Tue, 12 Apr 2016 12:44:31 -0400 Date: Tue, 12 Apr 2016 09:44:28 -0700 From: Kees Cook To: Linus Torvalds Cc: David Howells , Serge Hallyn , Willy Tarreau , Alexander Viro , linux-kernel@vger.kernel.org Subject: [PATCH] exec: clarify reasoning for euid/egid reset Message-ID: <20160412164428.GA1972@www.outflux.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 933 Lines: 33 This section of code initially looks redundant, but is required. This improves the comment to explain more clearly why the reset is needed. Signed-off-by: Kees Cook --- fs/exec.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/fs/exec.c b/fs/exec.c index c4010b8207a1..889221bbfdb3 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1387,7 +1387,12 @@ static void bprm_fill_uid(struct linux_binprm *bprm) kuid_t uid; kgid_t gid; - /* clear any previous set[ug]id data from a previous binary */ + /* + * Since this can be called multiple times (via prepare_binprm), + * we must clear any previous work done when setting set[ug]id + * bits from any earlier bprm->file uses (for example when run + * first for a script then for its interpreter). + */ bprm->cred->euid = current_euid(); bprm->cred->egid = current_egid(); -- 2.6.3 -- Kees Cook Chrome OS & Brillo Security