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 lists1p.gnu.org (lists1p.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 526E9CD4F49 for ; Mon, 18 May 2026 16:18:52 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1wP0fh-0006j0-On; Mon, 18 May 2026 12:18:25 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1wP0fg-0006ib-N0 for qemu-trivial@nongnu.org; Mon, 18 May 2026 12:18:24 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1wP0ff-0005D9-20 for qemu-trivial@nongnu.org; Mon, 18 May 2026 12:18:24 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1779121102; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=OZy0OU1N8ft6zOxGnJCl27Tw09WA7Y41+QRsOSq/xQw=; b=T2sVQRvA7EhKsv95XS/nZHxOU1dtWhCT842Y7gCLjX+RLN7yj0hFr/hK24qAOpBSf2lBoD TMUz0o9X19hm+8E8WBtzdH9s9NpmdxyzCIruCtVGMkfZVhbXXfJzdqnVnsGKn3kiiNLUgb mq8rHRR7SiQQj4C1/USTU9fEGPhtpBQ= Received: from mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-427-NlPZboUhMGGSGxH2Dm7Wtw-1; Mon, 18 May 2026 12:18:18 -0400 X-MC-Unique: NlPZboUhMGGSGxH2Dm7Wtw-1 X-Mimecast-MFC-AGG-ID: NlPZboUhMGGSGxH2Dm7Wtw_1779121098 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id ED95D195608F; Mon, 18 May 2026 16:18:17 +0000 (UTC) Received: from redhat.com (unknown [10.44.32.79]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 7A3CE30002DD; Mon, 18 May 2026 16:18:16 +0000 (UTC) Date: Mon, 18 May 2026 17:18:12 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Thomas Huth , qemu-devel@nongnu.org, qemu-trivial@nongnu.org Subject: Re: [PATCH] system/rtc: Fix a possible year-2038 integer overflow problem Message-ID: References: <20260518160255.1844308-1-thuth@redhat.com> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/2.3.1 (2026-03-20) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 X-Mimecast-MFC-PROC-ID: YHWYu0YxjRJqcQnTYOh4bdLKtZVcMK5mtvYjTj7draA_1779121098 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.445, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-trivial@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-trivial-bounces+qemu-trivial=archiver.kernel.org@nongnu.org Sender: qemu-trivial-bounces+qemu-trivial=archiver.kernel.org@nongnu.org On Mon, May 18, 2026 at 05:10:36PM +0100, Daniel P. Berrangé wrote: > On Mon, May 18, 2026 at 06:02:55PM +0200, Thomas Huth wrote: > > From: Thomas Huth > > > > rtc_realtime_clock_offset is initialized with: > > > > rtc_realtime_clock_offset = qemu_clock_get_ms(QEMU_CLOCK_REALTIME) / 1000; > > > > And QEMU_CLOCK_REALTIME might be based on gettimeofday() in certain > > cases (see get_clock_realtime() in include/qemu/timer.h). So this > > counter will exceed 32 bits in the year 2038, thus we should not > > store this value in a normal integer variable. Change it to an int64_t > > to fix the problem. > > And while we're at it, also adjust the nearby rtc_host_datetime_offset > > variable to be on the safe side in the related code. > > > > Signed-off-by: Thomas Huth > > --- > > system/rtc.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > Reviewed-by: Daniel P. Berrangé Actually on second reading I think this patch is not quite right. The code which uses the value is: time_t value = qemu_clock_get_ms(clock) / 1000; switch (clock) { case QEMU_CLOCK_REALTIME: value -= rtc_realtime_clock_offset; On 64-bit platforms 'int' was 64-bit already and so was time_t so we have no bug to fix. On 32-bit platforms the patch fixes 'int' to 'int64' which is fine but that int64 value is then subtracted from time_t which is usually going to be 32-bit again, unless the OS was built with 64-bit time_t on 32-bit which almost no one does. IOW we only platform this fixes is 32-bit OS with 64-bit time_t. We can't do any better than that as the caller code paths need a time_t to pass into gmtime/localtime. So IMHO we should just declare it as time_t. With regards, Daniel -- |: https://berrange.com ~~ https://hachyderm.io/@berrange :| |: https://libvirt.org ~~ https://entangle-photo.org :| |: https://pixelfed.art/berrange ~~ https://fstop138.berrange.com :|