From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with SMTP id 534626B0069 for ; Mon, 31 Oct 2011 11:32:57 -0400 (EDT) Date: Mon, 31 Oct 2011 16:28:33 +0100 From: Oleg Nesterov Subject: Re: [PATCH] oom: fix integer overflow of points in oom_badness Message-ID: <20111031152833.GA31904@redhat.com> References: <1320048865-13175-1-git-send-email-fhrbata@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1320048865-13175-1-git-send-email-fhrbata@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: Frantisek Hrbata Cc: rientjes@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, kosaki.motohiro@jp.fujitsu.com, minchan.kim@gmail.com, stable@kernel.org, eteo@redhat.com, pmatouse@redhat.com On 10/31, Frantisek Hrbata wrote: > > My understanding is that we may just change the type of points variable from int > to long and keep the current imho clearer(better readable) computation. There > should not be an overflow on 32bit and there is a plenty of space for 64bit. > If you like this solution better I will post the patch as v2. Up to maintainer, but personally I think the simple s/int/long/ looks better. Everything like get_mm_*/nr_ptes returns long. Anyway good catch. Imho stable needs the fix too. Cosmetic nit, > - points = get_mm_rss(p->mm) + p->mm->nr_ptes; > - points += get_mm_counter(p->mm, MM_SWAPENTS); > + points = (int)((get_mm_rss(p->mm) + get_mm_counter(p->mm, MM_SWAPENTS) + ^^^^^ Why do we need the explicit typecast? It buys nothing and looks a bit confusing. And, if you prefer "int", perhaps something like - points *= 1000; - points /= totalpages; + /* avoid the possible overflow */ + points = points * 1000L / totalpages; looks a bit more readable with the same effect. But I won't insist, this is up to you and David. Oleg. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org