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 76F92C44527 for ; Mon, 20 Jul 2026 10:39:20 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1wllOb-0003jX-DS; Mon, 20 Jul 2026 06:38:49 -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 1wllOW-0003jE-Ep for qemu-devel@nongnu.org; Mon, 20 Jul 2026 06:38:44 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1wllOU-0008Fp-6C for qemu-devel@nongnu.org; Mon, 20 Jul 2026 06:38:44 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1784543921; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=M1mbDPGNDDYLtz3dAfvpGEwZlm9V4lrrlmh7VeV1lw8=; b=OomYSHDdj0o0Ph82TkeM8wnuFeN7wuYSIUQHUlKwCa3ZX47uuMubJVSpiC/2LZlzTqsc8/ P50wj2opToswE4No0KhvRCE4FhAb/0T5a0n2wSkZMqZ0HV+mL1UAMKorZtxUUZTkrgA5Du 1mWin88yvrzAJDQVaLWn7S4AKgYgF+M= Received: from mx-prod-mc-03.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-554-3kCAbUIlPj-JDA4t0J-OAA-1; Mon, 20 Jul 2026 06:38:39 -0400 X-MC-Unique: 3kCAbUIlPj-JDA4t0J-OAA-1 X-Mimecast-MFC-AGG-ID: 3kCAbUIlPj-JDA4t0J-OAA_1784543919 Received: from mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.95]) (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-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 08F341944D39; Mon, 20 Jul 2026 10:38:39 +0000 (UTC) Received: from thuth-p1g4.redhat.com (unknown [10.44.34.82]) by mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 886C0158E; Mon, 20 Jul 2026 10:38:37 +0000 (UTC) From: Thomas Huth To: qemu-devel@nongnu.org, Stefan Hajnoczi Cc: Feifan Qian Subject: [PULL 1/7] hw/usb/xhci: clamp interval exponent to avoid UB shift in xhci_init_epctx() Date: Mon, 20 Jul 2026 12:38:27 +0200 Message-ID: <20260720103833.364506-2-thuth@redhat.com> In-Reply-To: <20260720103833.364506-1-thuth@redhat.com> References: <20260720103833.364506-1-thuth@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.6 on 10.30.177.95 Received-SPF: permerror client-ip=170.10.133.124; envelope-from=thuth@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 12 X-Spam_score: 1.2 X-Spam_bar: + X-Spam_report: (1.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, RCVD_IN_SBL_CSS=3.335, SPF_HELO_PASS=-0.001, T_SPF_PERMERROR=0.01 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: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org From: Feifan Qian The xHCI endpoint context dword 0 bits 23:16 ("Interval") are written by the guest and passed directly as the shift amount in: epctx->interval = 1 << ((ctx[0] >> 16) & 0xff); The shift amount can be 0-255. Shifting a 32-bit `int` left by >= 32 is undefined behaviour under C11 ยง6.5.7p4. With UBSan (halt_on_error=1) this causes QEMU to abort; with aggressive compiler optimisations that assume UB is unreachable the result is unpredictable. Clamp the exponent to [0, 18] with MIN() before the shift, and use `1u` (unsigned) to avoid shifting a signed integer. The xHCI specification defines a maximum meaningful Interval value of 18 for most endpoint types; thus clamping to 18 is a safe fix that preserves the full unsigned 32-bit range for any compliant value. Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3703 Reported-by: Feifan Qian Signed-off-by: Feifan Qian [thuth: Clamp to 18 instead of 31] Signed-off-by: Thomas Huth --- hw/usb/hcd-xhci.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/hw/usb/hcd-xhci.c b/hw/usb/hcd-xhci.c index c7e050e38fd..47b7484d533 100644 --- a/hw/usb/hcd-xhci.c +++ b/hw/usb/hcd-xhci.c @@ -1121,7 +1121,7 @@ static void xhci_init_epctx(XHCIEPContext *epctx, epctx->ring.ccs = ctx[2] & 1; } - epctx->interval = 1 << ((ctx[0] >> 16) & 0xff); + epctx->interval = 1u << MIN((ctx[0] >> 16) & 0xffu, 18u); } static TRBCCode xhci_enable_ep(XHCIState *xhci, unsigned int slotid, -- 2.55.0