Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261918AbVAHKIX (ORCPT ); Sat, 8 Jan 2005 05:08:23 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261858AbVAHKH5 (ORCPT ); Sat, 8 Jan 2005 05:07:57 -0500 Received: from parcelfarce.linux.theplanet.co.uk ([195.92.249.252]:29316 "EHLO www.linux.org.uk") by vger.kernel.org with ESMTP id S261918AbVAHKEl (ORCPT ); Sat, 8 Jan 2005 05:04:41 -0500 Date: Fri, 7 Jan 2005 20:12:55 -0200 From: Marcelo Tosatti To: Linus Torvalds Cc: Alan Cox , Lukasz Trabinski , Linux Kernel Mailing List Subject: Re: uselib() & 2.6.X? Message-ID: <20050107221255.GA8749@logos.cnet> References: <20050107170712.GK29176@logos.cnet> <1105136446.7628.11.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.5.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1785 Lines: 47 On Fri, Jan 07, 2005 at 04:15:28PM -0800, Linus Torvalds wrote: > > > On Fri, 7 Jan 2005, Alan Cox wrote: > > > > Please don't use that for mainline - do_brk_locked doesn't follow kernel > > convention > > I agree, I also find the "do_brk_locked()" naming confusing. To me it > implies that we already _are_ locked, not that we're going to lock. > > On the other hand, I think Alan's patch is equally confusing: the calling > rules for "do_brk()" and "do_mmap()" are the same, and they are "caller > takes mmap_sem". > > So I think you _both_ broke kernel conventions. > > So I'd personally much prefer to just first fix the bug minimally (by just > taking the lock in the two places that need it), and then _separately_ say > "we should warn if anybody ever calls 'do_brk()' without the lock". That's > how we tend to verify locking in other cases, ie we have things like > > if (!spin_is_locked(&t->sighand->siglock)) > BUG(); > > to verify the calling conventions. Same would go for mmap_sem (although we > don't seem to have any "sem_is_writelocked()" test - although you can fake > it with > > if (down_read_trylock(&mm->mmap_sem)) > BUG(); > > instead. > > Now _that_ is a non-silent failure mode. The machine doesn't just silently > deadlock: it tells you exactly what's wrong. Only problem is that current do_brk() callers dont take the lock - you would need a version of do_brk() that doesnt warn for them? But yes, the warning is better than silent failure or security problem for out-of-the tree users. - 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/