From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761921AbZEOKQr (ORCPT ); Fri, 15 May 2009 06:16:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756447AbZEOKQi (ORCPT ); Fri, 15 May 2009 06:16:38 -0400 Received: from e5.ny.us.ibm.com ([32.97.182.145]:54420 "EHLO e5.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755243AbZEOKQh (ORCPT ); Fri, 15 May 2009 06:16:37 -0400 Subject: Re: [PATCH] Fix Warnining in arch/x86/kernel/signal.c From: Subrata Modak Reply-To: subrata@linux.vnet.ibm.com To: Hiroshi Shimamoto Cc: "H. Peter Anvin" , Balbir Singh , Andi Kleen , Ingo Molnar , x86@kernel.org, Linux Kernel , Thomas Gleixner , Sachin P Sant , Andi Kleen , Ingo Molnar In-Reply-To: <4A0CE250.9050703@ct.jp.nec.com> References: <20090514091247.32082.38639.sendpatchset@subratamodak.linux.ibm.com> <4A0CE250.9050703@ct.jp.nec.com> Content-Type: text/plain Organization: IBM Date: Fri, 15 May 2009 15:46:31 +0530 Message-Id: <1242382591.7224.40.camel@subratamodak.linux.ibm.com> Mime-Version: 1.0 X-Mailer: Evolution 2.12.3 (2.12.3-8.el5_2.2) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2009-05-15 at 12:32 +0900, Hiroshi Shimamoto wrote: > Subrata Modak wrote: > > Hello Hiroshi-san, > > > > On Thu, 2009-05-14 at 09:24 +0900, Hiroshi Shimamoto wrote: > > H. Peter Anvin wrote: > >>> Ingo Molnar wrote: > >>>>>>> > >>>>>>> if (!access_ok(VERIFY_READ, frame, sizeof(*frame))) > >>>>>>> goto badframe; > >>>>>>> - if (__get_user(set.sig[0], &frame->sc.oldmask) || (_NSIG_WORDS > 1 > >>>>>>> - && __copy_from_user(&set.sig[1], &frame->extramask, > >>>>>>> - sizeof(frame->extramask)))) > >>>>>>> + > >>>>>>> + if ( (__copy_from_user(&set.sig[1], &frame->extramask, > >>>>>>> + sizeof(frame->extramask)) && _NSIG_WORDS > 1) || > >>>>>>> + __get_user(set.sig[0], &frame->sc.oldmask)) > >>>>>>> goto badframe; > >>>>>> I'm not sure why this eliminates that warning. > >>>>>> set.sig[0] may not be initialized too, if __copy_from_user() failed. > >>>>> True, but only when either or both of __copy_from_user() and > >>>>> (_NSIG_WORDS > 1) fails. But in all instances set.sig[1] gets > >>>>> initialized. > >>>>> > >>>>>> I don't have enough time to look at this right now, sorry. > >>>>>> > >>>>>> Another question, __copy_from_user() will be called even if > >>>>>> _NSIG_WORDS is less than 2, perhaps it never occurs. > >>>>>> I think, to check _NSIG_WORDS > 1 before calling __copy_from_user() > >>>>>> is better. > >>>>> Fine. Let Ingo/Thomas/Peter decide whether they would like this fix or > >>>>> drop it. > >>>> If you get the Acked-by from Hiroshi-san it looks good to me. He > >>>> modified this code last. > >>>> > >>> This seriously looks wrong to me. If _NSIG_WORDS == 1, then calling > >>> __copy_from_user here is a serious error. > >> Right. If _NSIG_WORDS is 1, sigset_t set has only sig[0], writing to > >> set.sig[1] means stack corruption. > >> > >> Subrata, could you try like this? > >> if ((_NSIG_WORDS > 1 && __copy_from_user(&set.sig[1], ...) || > >> __get_user(set.sig[0], ...)) > >> > >> > > > > How about now ? Thanks for pointing that out. My mistake ;-) > > Hi Subrata, I have a question. > Have you tried to compile on x86_64 whether the compiler claims the > similar code in sys32_sigreturn() in arch/x86/ia32/ia32_signal.c? Oops. No, the compiler does not complain here. It simply compiles fine. So, do you want to take a different view for the patch against arch/x86/kernel/signal.c, or, i would resend it with the following things fixed: > looks good to me. > BTW who writes the description? > > Acked-by: Hiroshi Shimamoto > Regards-- Subrata > > Thanks, > Hiroshi