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 A1541C531CB for ; Thu, 23 Jul 2026 12:45:15 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1wmsn8-0006xQ-Jt; Thu, 23 Jul 2026 08:44:46 -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 1wmsn7-0006wZ-Bo for qemu-trivial@nongnu.org; Thu, 23 Jul 2026 08:44:45 -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 1wmsn4-0000gY-VQ for qemu-trivial@nongnu.org; Thu, 23 Jul 2026 08:44:45 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1784810682; 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; bh=PVEgGZD0a4bNOPMUtuuMmfqj8NAr+4M4g6idRABiZhY=; b=i8HEmuWH92uhU7HdR19Mxiwyaqx29ln/jxHN36eK8ZtyrFWLjWw4wAkYI1U6pPtTdoF3bd BvTezMJmH2fEbm4CaN6TLCRdgnPRC9TnHWOrK1rtG51kTEzee5XHxf3K9Pikb6ZO0SD5vF Ob7AfaxANFEvATtmFuhDat8f/QI6Izs= 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 X-MC-Unique: dY4QxEl-MiumwqRmR_3NQA-1 X-Mimecast-MFC-AGG-ID: dY4QxEl-MiumwqRmR_3NQA_1784810677 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) 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 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 X-Mimecast-MFC-PROC-ID: g4WIkkE4hnGxnuL1mpcG3uOsGajQNpgoLXwV_NgU1_0_1784810677 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true 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-trivial@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-trivial-bounces+qemu-trivial=archiver.kernel.org@nongnu.org Sender: qemu-trivial-bounces+qemu-trivial=archiver.kernel.org@nongnu.org From: Thomas Huth The code in the SVGA_CMD_DEFINE_ALPHA_CURSOR handler in vmsvga_fifo_run() basically does: x = vmsvga_fifo_read(s); y = vmsvga_fifo_read(s); args = x * y; goto badcmd; ... badcmd: len -= 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 --- 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 = vmsvga_fifo_read(s); y = vmsvga_fifo_read(s); + if (x < 0 || x >= SVGA_MAX_WIDTH || + y < 0 || y >= SVGA_MAX_HEIGHT) { + goto rewind; + } args = 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", -- 2.55.0