From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933372AbdIYHUR (ORCPT ); Mon, 25 Sep 2017 03:20:17 -0400 Received: from mail-pg0-f68.google.com ([74.125.83.68]:37690 "EHLO mail-pg0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933073AbdIYHUO (ORCPT ); Mon, 25 Sep 2017 03:20:14 -0400 X-Google-Smtp-Source: AOwi7QAIUsyQ2x7EsgVXsqxMVKNzUfNdI3d7h+CrArpMCdhDkHO+HyWPXzfeEzNb7HMtOHvBZ/YKaQ== Date: Mon, 25 Sep 2017 00:20:10 -0700 From: Eric Biggers To: Ingo Molnar Cc: linux-kernel@vger.kernel.org, Andrew Morton , Andy Lutomirski , Borislav Petkov , Dave Hansen , Fenghua Yu , "H . Peter Anvin" , Linus Torvalds , Oleg Nesterov , Peter Zijlstra , Rik van Riel , Thomas Gleixner , Yu-cheng Yu Subject: Re: [PATCH 03/10] x86/fpu: Use validate_xstate_header() to validate the xstate_header in sanitize_restored_xstate() Message-ID: <20170925072010.GA25510@zzz.localdomain> References: <20170924105913.9157-1-mingo@kernel.org> <20170924105913.9157-4-mingo@kernel.org> <20170924185147.GA26260@zzz.localdomain> <20170924190242.hsbs7tqhvcalnczt@gmail.com> <20170924200853.GB26260@zzz.localdomain> <20170925061445.uzt5phqebwnvbhcb@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170925061445.uzt5phqebwnvbhcb@gmail.com> User-Agent: Mutt/1.9.0 (2017-09-02) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 25, 2017 at 08:14:45AM +0200, Ingo Molnar wrote: > > > > > > Could you please just send the delta patch against the whole tree to fix the bug? > > > I'll worry about the patch dependencies and back-merge it to the proper place. > > > > > > > The following diff against tip/master fixes the bug. Note: we *could* check > > 'use_xsave()' instead of 'state_size > offsetof(struct xregs_state, header)', > > but that might be confusing in the case where we couldn't find the xstate > > information in the memory layout and only copy the fxregs_state, since then we'd > > actually be validating the xsave_header which was already there, which shouldn't > > ever fail. > > > > diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c > > index afe54247cf27..fb639e70048f 100644 > > --- a/arch/x86/kernel/fpu/signal.c > > +++ b/arch/x86/kernel/fpu/signal.c > > @@ -331,7 +331,8 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size) > > err = copy_user_to_xstate(&fpu->state.xsave, buf_fx); > > } else { > > err = __copy_from_user(&fpu->state.xsave, buf_fx, state_size); > > - if (!err) > > + > > + if (!err && state_size > offsetof(struct xregs_state, header)) > > err = validate_xstate_header(&fpu->state.xsave.header); > > } > > I.e. a better check would be to check that the whole header can be accessed: > > state_size >= offsetof(struct xregs_state, header) + sizeof(struct xstate_header) > > Not that there should ever be a 'state_size' that points inside the header - so in > the end I back-merged your original (and tested ...) version. > Well, actually we'd need to validate the header if userspace overwrote any part of it. But more importantly, I think the state_size check needs to go into the first patch (the one that's Cc'ed to stable as it fixes the real bug), since ->xcomp_bv is part of the xstate_header. So *before* we switch to validate_xstate_header() in this patch, the code should already be: if (using_compacted_format()) { err = copy_user_to_xstate(&fpu->state.xsave, buf_fx); } else { err = __copy_from_user(&fpu->state.xsave, buf_fx, state_size); /* xcomp_bv must be 0 when using uncompacted format */ if (!err && state_size > offsetof(struct xregs_state, header) && fpu->state.xsave.header.xcomp_bv) err = -EINVAL; } Also can you please fix the commit title and message of this patch? It should say "__fpu__restore_sig()", not "sanitize_restored_xstate()". Thanks, Eric