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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9BD9EC433EF for ; Thu, 11 Nov 2021 17:07:36 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 0895261211 for ; Thu, 11 Nov 2021 17:07:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 0895261211 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=nuviainc.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:54086 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mlDXy-00050H-OW for qemu-devel@archiver.kernel.org; Thu, 11 Nov 2021 12:07:34 -0500 Received: from eggs.gnu.org ([209.51.188.92]:37876) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mlDVV-0003Qh-OP for qemu-devel@nongnu.org; Thu, 11 Nov 2021 12:05:01 -0500 Received: from [2a00:1450:4864:20::534] (port=33343 helo=mail-ed1-x534.google.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1mlDVT-0001Lv-Dk for qemu-devel@nongnu.org; Thu, 11 Nov 2021 12:05:01 -0500 Received: by mail-ed1-x534.google.com with SMTP id m14so27099187edd.0 for ; Thu, 11 Nov 2021 09:04:58 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nuviainc-com.20210112.gappssmtp.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to; bh=yj8x04XlMGJcyZqCdVRk32Ff9/mIwqZahMzALG2V8j8=; b=ztd6W2fMaDQhLVsOCVcIHm4nvHEk4R7VDY79zYU/JRMWnxKnsIRGdfM6AZXHc4+ZMI xzgR5Av9mJLTR2BMGbhBzZp8C8WLx3ZVS75LdBkAoiTyohKEXAFUYeuC9aPyDh2YaHG2 xLGUr+JFFKVfCQcG50UYOKUNoIcUXiYFYjLiz/MjCSdCTv/GNmR3kk8/lm1tQam+LrT4 9nAnLfz19iCEWpECIv7HBKIHtIw7Tk4zsWlIDW5VMNgWYGRMf+nf/GrfGEAm63d0LXrR SAIsboAebx+3K4IbO/hZQfylC2qAVhoHqtMpy8446PB1a8zuAU1P24wxafBYPy7GJANq GQYg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to; bh=yj8x04XlMGJcyZqCdVRk32Ff9/mIwqZahMzALG2V8j8=; b=YeQ0vgHlYSjN0U7QXtFnT/LTvxFodKMbyDVd5ahWh+jKTtVWwNxsgYKfcEVm3Wx8/6 j46O598YPY4M/vAY6QZ902p1P6u3ojmrd/3U2GqjPrfTzo4mf0osMVVhfI1oEH4dKjTW CBVRfJZHaM1KzVxdC2gGLRfWSjzVYQuasEoh3n0DoTDZMHyjqdlYAqgrzPFqw0eT73ma lx8kFcboByt7VVRPQl2EVmp5uQaOtuinqjsK2rxXpCrO3qMAVfShR4AoJnGDzwzL2r51 o2ZwE41A/VO1NEnb7u32trkzf5F+HnYDWFa2FvE8HnTVOW6d/WusFly6dKfg981HHbkE Fv+w== X-Gm-Message-State: AOAM530sMMKT77oto1iDNL6f1MsZqruxjg1Mr0I8l9W1iDTtYxXs48DP TciBhgiar+Jbm7ZZVdbxQefoRg== X-Google-Smtp-Source: ABdhPJxV2V8nKe99CM7//KuAOngZroQA6KesL6jEQXAH3q8RgsX4ZpEFmRPZdZajsY5YnlUlB9CTEQ== X-Received: by 2002:aa7:d155:: with SMTP id r21mr11938026edo.341.1636650297298; Thu, 11 Nov 2021 09:04:57 -0800 (PST) Received: from localhost ([82.44.17.50]) by smtp.gmail.com with ESMTPSA id e19sm1881048edu.47.2021.11.11.09.04.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 11 Nov 2021 09:04:56 -0800 (PST) Date: Thu, 11 Nov 2021 17:04:56 +0000 From: Jamie Iles To: Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= Subject: Re: [PATCH 2/2] hw/core/loader: workaround read() size limit. Message-ID: References: <20211111141141.3295094-1-jamie@nuviainc.com> <20211111141141.3295094-3-jamie@nuviainc.com> <7e490883-b723-1ff6-9191-6ef0c91ccd25@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <7e490883-b723-1ff6-9191-6ef0c91ccd25@redhat.com> X-Host-Lookup-Failed: Reverse DNS lookup failed for 2a00:1450:4864:20::534 (failed) Received-SPF: pass client-ip=2a00:1450:4864:20::534; envelope-from=jamie@nuviainc.com; helo=mail-ed1-x534.google.com X-Spam_score_int: -10 X-Spam_score: -1.1 X-Spam_bar: - X-Spam_report: (-1.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, PDS_HP_HELO_NORDNS=0.001, RCVD_IN_DNSWL_NONE=-0.0001, RDNS_NONE=0.793, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jamie Iles , qemu-devel@nongnu.org, lmichel@kalray.eu Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Nov 11, 2021 at 04:55:35PM +0100, Philippe Mathieu-Daudé wrote: > On 11/11/21 16:43, Philippe Mathieu-Daudé wrote: > > On 11/11/21 16:36, Jamie Iles wrote: > >> Hi Philippe, > >> > >> On Thu, Nov 11, 2021 at 03:55:48PM +0100, Philippe Mathieu-Daudé wrote: > >>> Hi Jamie, > >>> > >>> On 11/11/21 15:11, Jamie Iles wrote: > >>>> On Linux, read() will only ever read a maximum of 0x7ffff000 bytes > >>>> regardless of what is asked. If the file is larger than 0x7ffff000 > >>>> bytes the read will need to be broken up into multiple chunks. > >>>> > >>>> Cc: Luc Michel > >>>> Signed-off-by: Jamie Iles > >>>> --- > >>>> hw/core/loader.c | 40 ++++++++++++++++++++++++++++++++++------ > >>>> 1 file changed, 34 insertions(+), 6 deletions(-) > >>>> > >>>> diff --git a/hw/core/loader.c b/hw/core/loader.c > >>>> index 348bbf535bd9..16ca9b99cf0f 100644 > >>>> --- a/hw/core/loader.c > >>>> +++ b/hw/core/loader.c > >>>> @@ -80,6 +80,34 @@ int64_t get_image_size(const char *filename) > >>>> return size; > >>>> } > >>>> > >>>> +static ssize_t read_large(int fd, void *dst, size_t len) > >>>> +{ > >>>> + /* > >>>> + * man 2 read says: > >>>> + * > >>>> + * On Linux, read() (and similar system calls) will transfer at most > >>>> + * 0x7ffff000 (2,147,479,552) bytes, returning the number of bytes > >>> > >>> Could you mention MAX_RW_COUNT from linux/fs.h? > >>> > >>>> + * actually transferred. (This is true on both 32-bit and 64-bit > >>>> + * systems.) > >>> > >>> Maybe "This is true for both ILP32 and LP64 data models used by Linux"? > >>> (because that would not be the case for the ILP64 model). > >>> > >>> Otherwise s/systems/Linux variants/? > >>> > >>>> + * > >>>> + * So read in chunks no larger than 0x7ffff000 bytes. > >>>> + */ > >>>> + size_t max_chunk_size = 0x7ffff000; > >>> > >>> We can declare it static const. > >> > >> Ack, can fix all of those up. > >> > >>>> + size_t offset = 0; > >>>> + > >>>> + while (offset < len) { > >>>> + size_t chunk_len = MIN(max_chunk_size, len - offset); > >>>> + ssize_t br = read(fd, dst + offset, chunk_len); > >>>> + > >>>> + if (br < 0) { > >>>> + return br; > >>>> + } > >>>> + offset += br; > >>>> + } > >>>> + > >>>> + return (ssize_t)len; > >>>> +} > >>> > >>> I see other read()/pread() calls: > >>> > >>> hw/9pfs/9p-local.c:472: tsize = read(fd, (void *)buf, bufsz); > >>> hw/vfio/common.c:269: if (pread(vbasedev->fd, &buf, size, > >>> region->fd_offset + addr) != size) { > >>> ... > >>> > >>> Maybe the read_large() belongs to "sysemu/os-xxx.h"? > >> > >> I think util/osdep.c would be a good fit for this. To make sure we're > > > > Yes. > > > >> on the same page though are you proposing converting all pread/read > >> calls to a qemu variant or auditing for ones that could potentially take > >> a larger size? > > > > Yes, I took some time wondering beside loading blob in guest memory, > > what would be the other issues you might encounter. I couldn't find > > many cases. Eventually hw/vfio/. I haven't audit much, only noticed > > hw/9pfs/9p-local.c and qga/commands-*.c (not sure if relevant), but > > since we want to fix this, I'd rather try to fix it globally. > > Actually what you suggest is simpler, add qemu_read() / qemu_pread() > in util/osdep.c, convert all uses without caring about any audit. Okay, this hasn't worked out too badly - I'll do the same for write/pwrite too and then switch all of the callers over with a coccinelle patch so it'll be a fairly large diff but simple. We could elect to keep any calls with a compile-time constant length with the unwrapped variants but I think that's probably more confusing in the long-run. Thanks, Jamie