Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756589Ab3HFUVw (ORCPT ); Tue, 6 Aug 2013 16:21:52 -0400 Received: from mail-pa0-f43.google.com ([209.85.220.43]:62091 "EHLO mail-pa0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756423Ab3HFUVv (ORCPT ); Tue, 6 Aug 2013 16:21:51 -0400 Message-ID: <52015ADB.30408@mit.edu> Date: Tue, 06 Aug 2013 13:21:47 -0700 From: Andy Lutomirski User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130625 Thunderbird/17.0.7 MIME-Version: 1.0 To: Chen Gang CC: Kees Cook , Al Viro , Oleg Nesterov , holt@sgi.com, Andrew Morton , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 1/2] kernel/sys.c: return the current gid when error occurs References: <5200AD26.8070701@asianux.com> <5200AD67.1030109@asianux.com> In-Reply-To: <5200AD67.1030109@asianux.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1486 Lines: 42 On 08/06/2013 01:01 AM, Chen Gang wrote: > According to the API definition, when error occurs, need return current > fsgid instead of the previous one. > > The related informations ("man setfsgid"): > > RETURN VALUE > On success, the previous value of fsgid is returned. On error, the current value of fsgid is returned. > > Signed-off-by: Chen Gang > --- > kernel/sys.c | 6 +++--- > 1 files changed, 3 insertions(+), 3 deletions(-) > > diff --git a/kernel/sys.c b/kernel/sys.c > index 771129b..9356dc8 100644 > --- a/kernel/sys.c > +++ b/kernel/sys.c > @@ -775,11 +775,11 @@ SYSCALL_DEFINE1(setfsgid, gid_t, gid) > > kgid = make_kgid(old->user_ns, gid); > if (!gid_valid(kgid)) > - return old_fsgid; > + return gid; Huh? So if 1234567 is not a valid gid, then setfsgid(1234567) is supposed to return 1234567? This makes no sense. I assume that what the man page means is that the return value is whatever fsgid was prior to the call. On error, fsgid isn't changed, so the return value is still "current". (FWIW, this behavior is awful and is probably the cause of a security bug or three, since success and failure are indistinguishable. But I think your patch is wrong.) --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/