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 1557BC433FE for ; Sun, 20 Nov 2022 01:40:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229520AbiKTBkJ (ORCPT ); Sat, 19 Nov 2022 20:40:09 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35956 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229499AbiKTBkI (ORCPT ); Sat, 19 Nov 2022 20:40:08 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1AFB0B94AD; Sat, 19 Nov 2022 17:40:08 -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 A402060BCB; Sun, 20 Nov 2022 01:40:07 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9F92EC433D6; Sun, 20 Nov 2022 01:40:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1668908406; bh=mB2/5SFy2jr4OJagL4mr8wczTaB3RfCbSmiQnv5noa4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=G5nq+us05sEucQ4RJRBz5n6pXnWIBxZo6AvKSt7WtLvvmxC2q8kgGEci49G0FEKMT R0cptdirpgBxNX303fr0yMWEkWQw4j1e42S21cywB1YXa9hGiDHaS65lvGeJX6KjMs Jyq30v5N2jWc2hmdwGXwQnoIiFRX9YR8dY8OyiGoMIg1Xm0QI32iXwilgwpTvLFGP3 tnmHb+371mqvMfXx0zl9lDXExjGT7NV9sorUk3JCI1ISrRMggtGpY22Dsu7t0VeaCl vVOdQTp5OmwjeP1qjPYYIbl7HnMJT89KpssX5Q7Z8du7uEPNmvxbjwIl9jzh7weVMf sstirvDV/4+1w== Date: Sat, 19 Nov 2022 17:40:04 -0800 From: Eric Biggers To: "Jason A. Donenfeld" 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=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org 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)); - Eric