From nobody Fri Jul 24 05:21:55 2026 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass(p=quarantine dis=none) header.from=redhat.com ARC-Seal: i=1; a=rsa-sha256; t=1784810704; cv=none; d=zohomail.com; s=zohoarc; b=HL8DZr+cme3sDbvF0hcN9837WRjpQE+SNr6hpdLMOzAyaFDYoRtFvAH2DyhGBxbKUSq1ifziuvr8NRbKv4rgrR6rjnxjnlAyIyrGtBK5Szgc1P+6clA4+y+J7IhEu6Y0FSoqxieg9IeHg4/lSqeBBUEEAQl/qenBEuZPA6bSmcQ= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1784810704; h=Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:Sender:Subject:Subject:To:To:Message-Id:Reply-To; bh=PVEgGZD0a4bNOPMUtuuMmfqj8NAr+4M4g6idRABiZhY=; b=gIrlcVHMCO6f+JTwQuQSXpR2XTVg9/6RxplQIWk9Q3TtMu9IBdEpFeulkr5psNMRhxxvoahIGElK2WIB8ECKuKAEJoUhlqCwiyhS6Rkv/9MjNC5T74eyvbuDAjvGicXDb0uHHFk5IMy8vN/PuSRXz7yW0L6qy2tXje8lPKhVHXY= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass header.from= (p=quarantine dis=none) Return-Path: Received: from lists1p.gnu.org (lists1p.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1784810704202873.2952358162107; Thu, 23 Jul 2026 05:45:04 -0700 (PDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1wmsn7-0006wr-Nf; Thu, 23 Jul 2026 08:44:45 -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 1wmsn6-0006wI-7P for qemu-devel@nongnu.org; Thu, 23 Jul 2026 08:44:44 -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 1wmsn3-0000gM-Rz for qemu-devel@nongnu.org; Thu, 23 Jul 2026 08:44:43 -0400 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-156-dY4QxEl-MiumwqRmR_3NQA-1; Thu, 23 Jul 2026 08:44:38 -0400 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (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 9AEEF1945CB6; Thu, 23 Jul 2026 12:44:37 +0000 (UTC) Received: from thuth-p1g4.redhat.com (unknown [10.44.32.74]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 1AB721956053; Thu, 23 Jul 2026 12:44:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1784810680; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=PVEgGZD0a4bNOPMUtuuMmfqj8NAr+4M4g6idRABiZhY=; b=GDATL1jCecFttaOJGc/j+ckxcQIQi6l9GmB4GeMo3+aeX/VAvZV8QsLSHdJyP35lsXLeJj wbLEiBP8bp9+fyA+qfLsvaln3CrTMkNDm/jdBFOr5brmAiQlgHOQRiH3DcvmXoIdXbrR1f lOMXwF5/2p3rbaQRLnkVqWECWDQ+yIo= X-MC-Unique: dY4QxEl-MiumwqRmR_3NQA-1 X-Mimecast-MFC-AGG-ID: dY4QxEl-MiumwqRmR_3NQA_1784810677 From: Thomas Huth To: qemu-devel@nongnu.org, Dmitry Fleytman Cc: qemu-trivial@nongnu.org, qemu-stable@nongnu.org Subject: [PATCH v2] hw/display/vmware_vga: Don't allow guest to trigger long running loop in host Date: Thu, 23 Jul 2026 14:44:32 +0200 Message-ID: <20260723124432.353969-1-thuth@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists1p.gnu.org; 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: 3 X-Spam_score: 0.3 X-Spam_bar: / X-Spam_report: (0.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.951, 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=0.001, RCVD_IN_MSPIKE_WL=0.001, 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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1784810705358158500 Content-Type: text/plain; charset="utf-8" From: Thomas Huth The code in the SVGA_CMD_DEFINE_ALPHA_CURSOR handler in vmsvga_fifo_run() basically does: x =3D vmsvga_fifo_read(s); y =3D vmsvga_fifo_read(s); args =3D x * y; goto badcmd; ... badcmd: len -=3D args; if (len < 0) { goto rewind; } while (args--) { vmsvga_fifo_read(s); } Thus by supplying huge values for x and y that overflow the result of the multiplication, the guest can trigger a long-running loop here that burns the host's CPU cycles. Add some sanity checks so that this cannot happen anymore. Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3782 Reported-by: Feifan Qian Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/4026 Reported-by: Tristan Madani Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/4076 Reported-by: Sunday Jiang Signed-off-by: Thomas Huth Reviewed-by: Philippe Mathieu-Daud=C3=A9 --- v2: Use SVGA_MAX_WIDTH and SVGA_MAX_HEIGHT instead of an arbitrary value hw/display/vmware_vga.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/hw/display/vmware_vga.c b/hw/display/vmware_vga.c index f6f9edfd1d9..567806f0e47 100644 --- a/hw/display/vmware_vga.c +++ b/hw/display/vmware_vga.c @@ -737,6 +737,10 @@ static void vmsvga_fifo_run(struct vmsvga_state_s *s) vmsvga_fifo_read(s); x =3D vmsvga_fifo_read(s); y =3D vmsvga_fifo_read(s); + if (x < 0 || x >=3D SVGA_MAX_WIDTH || + y < 0 || y >=3D SVGA_MAX_HEIGHT) { + goto rewind; + } args =3D x * y; goto badcmd; case SVGA_CMD_RECT_ROP_FILL: @@ -776,7 +780,7 @@ static void vmsvga_fifo_run(struct vmsvga_state_s *s) if (len < 0) { goto rewind; } - while (args--) { + while (args-- > 0) { vmsvga_fifo_read(s); } printf("%s: Unknown command 0x%02x in SVGA command FIFO\n", --=20 2.55.0