From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6B71EC433FE for ; Sun, 20 Nov 2022 01:45:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229514AbiKTBpp (ORCPT ); Sat, 19 Nov 2022 20:45:45 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37182 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229480AbiKTBpo (ORCPT ); Sat, 19 Nov 2022 20:45:44 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B5515B6B26; Sat, 19 Nov 2022 17:45:43 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 51E1660B8C; Sun, 20 Nov 2022 01:45:43 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C05BEC433D6; Sun, 20 Nov 2022 01:45:41 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="F76kpxsD" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1668908739; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=AO3FumHniHDYxypWhfcaQ48Un3bhenW0ecmpQ/0bPjI=; b=F76kpxsDPEDB62/aj2fUMTpZEYLD0x3o2jlPxMiQuLsVPn2PrDcc191NSzYK8HNgcknCoo tMl5eYvJHuDQ1doO8v2Nmm5bWgqldkgRNkNkdQ8MNnL03yNq7pwCCZ0nkcAqkq2KBXDdgG CRMJqsqeH0ZmXNYYeg4JYCPeUpKdojU= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id 28f55c2f (TLSv1.3:TLS_AES_256_GCM_SHA384:256:NO); Sun, 20 Nov 2022 01:45:39 +0000 (UTC) Date: Sun, 20 Nov 2022 02:45:37 +0100 From: "Jason A. Donenfeld" To: Eric Biggers Cc: linux-kernel@vger.kernel.org, patches@lists.linux.dev, linux-crypto@vger.kernel.org, x86@kernel.org, Thomas Gleixner , Greg Kroah-Hartman , Adhemerval Zanella Netto , Carlos O'Donell Subject: Re: [PATCH v5 1/3] random: add vgetrandom_alloc() syscall Message-ID: References: <20221119120929.2963813-1-Jason@zx2c4.com> <20221119120929.2963813-2-Jason@zx2c4.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org On Sat, Nov 19, 2022 at 05:40:04PM -0800, Eric Biggers wrote: > On Sun, Nov 20, 2022 at 12:59:07AM +0100, Jason A. Donenfeld wrote: > > Hi Eric, > > > > On Sat, Nov 19, 2022 at 12:39:26PM -0800, Eric Biggers wrote: > > > On Sat, Nov 19, 2022 at 01:09:27PM +0100, Jason A. Donenfeld wrote: > > > > +SYSCALL_DEFINE3(vgetrandom_alloc, unsigned long __user *, num, > > > > + unsigned long __user *, size_per_each, unsigned int, flags) > > > > +{ > > > > + unsigned long alloc_size; > > > > + unsigned long num_states; > > > > + unsigned long pages_addr; > > > > + int ret; > > > > + > > > > + if (flags) > > > > + return -EINVAL; > > > > + > > > > + if (get_user(num_states, num)) > > > > + return -EFAULT; > > > > + > > > > + alloc_size = size_mul(num_states, sizeof(struct vgetrandom_state)); > > > > + if (alloc_size == SIZE_MAX) > > > > + return -EOVERFLOW; > > > > + alloc_size = roundup(alloc_size, PAGE_SIZE); > > > > > > Small detail: the roundup to PAGE_SIZE can make alloc_size overflow to 0. > > > > > > Also, 'roundup(alloc_size, PAGE_SIZE)' could be 'PAGE_ALIGN(alloc_size)'. > > > > Good catch, thanks. So perhaps this? > > > > alloc_size = size_mul(num_states, sizeof(struct vgetrandom_state)); > > if (alloc_size > SIZE_MAX - PAGE_SIZE + 1) > > return -EOVERFLOW; > > alloc_size = PAGE_ALIGN(alloc_size); > > > > Does that look right? > > Yes. Maybe use 'SIZE_MAX & PAGE_MASK'? > > Another alternative is the following: > > if (num_states > > (SIZE_MAX & PAGE_MASK) / sizeof(struct vgetrandom_state)) > return -EOVERFLOW; > alloc_size = PAGE_ALIGN(num_states * sizeof(struct vgetrandom_state)); Thanks, that's much nicer. Jason