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 A968CC44527 for ; Mon, 20 Jul 2026 10:39:56 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1wllOl-0003m4-RZ; Mon, 20 Jul 2026 06:38:59 -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 1wllOc-0003kK-Cv for qemu-devel@nongnu.org; Mon, 20 Jul 2026 06:38:51 -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 1wllOa-0008Gg-Ps for qemu-devel@nongnu.org; Mon, 20 Jul 2026 06:38:50 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1784543928; 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=h9gHWXrpug65VRTeYXgdUAFcY9n2qUEl8WfpF47AYrQ=; b=c4CXDDVuIPAg6UUi2l4lBBdH3VLsTBWnhxLzlSC75QNRIF02rydFWpLLjpEYkoeDPABcdg rOSycGXBbooo4NMRDxZisY9Hr8b6uPQMWvkkcjz9S3NhK8M/cGkz875SkztrHVkJlXbz4X q6H+ITmLFYesMowzOqQrRiiIGMglmC8= 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-681-xRBc717gMwuvjdn5_m0gNA-1; Mon, 20 Jul 2026 06:38:46 -0400 X-MC-Unique: xRBc717gMwuvjdn5_m0gNA-1 X-Mimecast-MFC-AGG-ID: xRBc717gMwuvjdn5_m0gNA_1784543926 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 CF4921955F22; Mon, 20 Jul 2026 10:38:45 +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 32D4F158E; Mon, 20 Jul 2026 10:38:43 +0000 (UTC) From: Thomas Huth To: qemu-devel@nongnu.org, Stefan Hajnoczi Cc: Feifan Qian , =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= Subject: [PULL 4/7] usbredir: fix use-after-free on buffered bulk packet overflow Date: Mon, 20 Jul 2026 12:38:30 +0200 Message-ID: <20260720103833.364506-5-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=170.10.129.124; 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_H2=-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: Marc-André Lureau When usbredir_buffered_bulk_packet() splits a multi-fragment buffered bulk packet into max-packet-size chunks, only the final fragment owns the shared parser allocation (via free_on_destroy). If bufp_alloc() drops the final fragment due to queue overflow, it frees the backing buffer while earlier fragments already queued still hold interior pointers into it. Subsequent guest bulk-IN transfers then read from freed heap memory. Fix this by tracking how many fragments were queued during the current packet. When bufp_alloc() fails, remove all already-queued fragments from the tail of the endpoint queue before breaking out of the loop. If the dropped fragment was non-final, free the data buffer explicitly since no fragment took ownership. Fixes: CVE-2026-15705 Fixes: b2d1fe67d09d ("usbredir: Add support for buffered bulk input (v2)") Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3808 Reported-by: Feifan Qian Signed-off-by: Marc-André Lureau Message-ID: <20260714185717.1156157-1-marcandre.lureau@redhat.com> Signed-off-by: Thomas Huth --- hw/usb/redirect.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) diff --git a/hw/usb/redirect.c b/hw/usb/redirect.c index bde821e214b..284bcbdb34d 100644 --- a/hw/usb/redirect.c +++ b/hw/usb/redirect.c @@ -2138,7 +2138,7 @@ static void usbredir_buffered_bulk_packet(void *priv, uint64_t id, USBRedirDevice *dev = priv; uint8_t status, ep = buffered_bulk_packet->endpoint; void *free_on_destroy; - int i, len; + int i, len, queued = 0; DPRINTF("buffered-bulk-in status %d ep %02X len %d id %"PRIu64"\n", buffered_bulk_packet->status, ep, data_len, id); @@ -2169,8 +2169,24 @@ static void usbredir_buffered_bulk_packet(void *priv, uint64_t id, /* bufp_alloc also adds the packet to the ep queue */ r = bufp_alloc(dev, data + i, len, status, ep, free_on_destroy); if (r) { + /* + * Earlier fragments from this packet are in the queue + * with interior pointers into data. If the dropped + * fragment was the final one, bufp_alloc already freed + * data so those pointers are dangling. Remove them. + */ + while (queued > 0) { + struct buf_packet *bufp; + bufp = QTAILQ_LAST(&dev->endpoint[EP2I(ep)].bufpq); + bufp_free(dev, bufp, ep); + queued--; + } + if (!free_on_destroy) { + free(data); + } break; } + queued++; } if (dev->endpoint[EP2I(ep)].pending_async_packet) { -- 2.55.0