From nobody Sat Jul 25 16:21:38 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=1784188587; cv=none; d=zohomail.com; s=zohoarc; b=H60JzdvTvCKCPBKysTrpPCyQMIMGFlY88qKXueMDTLkLExlC1x61NMOGH4y7Mx+aYpDxET8s9vEG0xhapipoBo/hIJjqM/E2I4E3jgua7dB1HTTJ1kNFPV7Fxk+zxfU53QRvygYVnVjjapaOJ8nGzjwNyQ5HvGov7mW0Y4p7e4A= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1784188587; h=Content-Type: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=HGA/S3rRc7S5CSXQLWGAi3tEFZeLtR8B6kZNbrWEQz8=; b=FLwzN2ENIX7rnqFAy5zRRTcfKP4yK6avfqAxLSQz5yU7FDBZzf6BogD8zZo4AcRwjkO5Np6QSnb1dtNA5F3+9FqiGw21qZpV+sUniHcsy5jAo1F2mmLuroRTz670hOvCVLHuE+T+8YqOfLuKF8aIBZExXFd9fJfYfOSWHiIplNc= 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 1784188587507506.10984807916077; Thu, 16 Jul 2026 00:56:27 -0700 (PDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1wkGwd-0007au-Eo; Thu, 16 Jul 2026 03:55:47 -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 1wkGwa-0007Ug-B0 for qemu-devel@nongnu.org; Thu, 16 Jul 2026 03:55:44 -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 1wkGwX-0003yo-Na for qemu-devel@nongnu.org; Thu, 16 Jul 2026 03:55:44 -0400 Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-138-AzynUMvtOa-2SNTAXnSv2w-1; Thu, 16 Jul 2026 03:55:36 -0400 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id E7B211800623; Thu, 16 Jul 2026 07:55:34 +0000 (UTC) Received: from localhost (unknown [10.44.22.17]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 5133C1800283; Thu, 16 Jul 2026 07:55:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1784188540; 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=HGA/S3rRc7S5CSXQLWGAi3tEFZeLtR8B6kZNbrWEQz8=; b=N0tayDmEhyW8i03Oc/pVNIQEWyyUt5StW82lmvAVZFwtioFYeBdF37OOxDIvMa9MTwrWcn xF4Nts1Pu5YisNtyXTXNA2KpQiWXyIGU65FOur4zzjNEKcicdSbnppmw2R5bPa1T8HoP+9 Po/6+4Czti4NxmRXy2ufrdWNlFUUWfE= X-MC-Unique: AzynUMvtOa-2SNTAXnSv2w-1 X-Mimecast-MFC-AGG-ID: AzynUMvtOa-2SNTAXnSv2w_1784188535 From: marcandre.lureau@redhat.com To: qemu-devel@nongnu.org Cc: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= , "Michael S. Tsirkin" , =?UTF-8?q?Alex=20Benn=C3=A9e?= , Akihiko Odaki , Dmitry Osipenko Subject: [PATCH] hw/display/virtio-gpu: cap submit_3d command buffer allocation Date: Thu, 16 Jul 2026 11:55:29 +0400 Message-ID: <20260716075529.3009491-1-marcandre.lureau@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 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=marcandre.lureau@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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, SPF_HELO_PASS=-0.001, T_SPF_PERMERROR=0.01 autolearn=ham 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: 1784188589856158500 From: Marc-Andr=C3=A9 Lureau Both virgl_cmd_submit_3d() and rutabaga_cmd_submit_3d() pass the guest-controlled cs.size directly to malloc() without bounds checking. A malicious guest can set cs.size to an arbitrarily large value, causing an OOM abort that crashes the QEMU process. Checking cs.size against the descriptor payload length (iov_size) is not sufficient: indirect descriptor tables can repeat entries aliasing the same guest-physical range, inflating iov_size() to nearly 4 GiB while referring to only a small amount of unique memory. Instead, cap cs.size at 4 MiB. With 4 KiB pages and QEMU's VIRTQUEUE_MAX_SIZE (1024) mapped-iov limit, the Linux virtio driver cannot carry more than ~4 MiB of inline command data, so legitimate submissions are unaffected. Fixes: 9d9e152136bd ("virtio-gpu: add 3d mode and virgl rendering support.") Fixes: 1dcc6adbc168 ("gfxstream + rutabaga: add initial support for gfxstre= am") Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3776 Reported-by: admin@fluentlogic.org Signed-off-by: Marc-Andr=C3=A9 Lureau --- include/hw/virtio/virtio-gpu.h | 8 ++++++++ hw/display/virtio-gpu-rutabaga.c | 8 ++++++++ hw/display/virtio-gpu-virgl.c | 8 ++++++++ 3 files changed, 24 insertions(+) diff --git a/include/hw/virtio/virtio-gpu.h b/include/hw/virtio/virtio-gpu.h index f69fc194627..c10bfbd596f 100644 --- a/include/hw/virtio/virtio-gpu.h +++ b/include/hw/virtio/virtio-gpu.h @@ -299,6 +299,14 @@ struct VirtIOGPURutabaga { struct rutabaga *rutabaga; }; =20 +/* + * With 4 KiB pages and QEMU's VIRTQUEUE_MAX_SIZE (1024) mapped-iov + * limit, the largest inline command is ~4 MiB. Cap submit_3d + * allocations to this value to prevent a malicious guest from + * triggering an OOM abort via an inflated cs.size field. + */ +#define VIRTIO_GPU_MAX_CMD_SUBMIT_SIZE (4 * 1024 * 1024) + #define VIRTIO_GPU_FILL_CMD(out) do { \ size_t virtiogpufillcmd_s_ =3D \ iov_to_buf(cmd->elem.out_sg, cmd->elem.out_num, 0, \ diff --git a/hw/display/virtio-gpu-rutabaga.c b/hw/display/virtio-gpu-rutab= aga.c index 6ff12639012..4d7d7b24592 100644 --- a/hw/display/virtio-gpu-rutabaga.c +++ b/hw/display/virtio-gpu-rutabaga.c @@ -351,6 +351,14 @@ rutabaga_cmd_submit_3d(VirtIOGPU *g, VIRTIO_GPU_FILL_CMD(cs); trace_virtio_gpu_cmd_ctx_submit(cs.hdr.ctx_id, cs.size); =20 + if (cs.size > VIRTIO_GPU_MAX_CMD_SUBMIT_SIZE) { + qemu_log_mask(LOG_GUEST_ERROR, + "%s: command buffer too large (%u)\n", + __func__, cs.size); + cmd->error =3D VIRTIO_GPU_RESP_ERR_INVALID_PARAMETER; + return; + } + buf =3D g_new0(uint8_t, cs.size); s =3D iov_to_buf(cmd->elem.out_sg, cmd->elem.out_num, sizeof(cs), buf, cs.size); diff --git a/hw/display/virtio-gpu-virgl.c b/hw/display/virtio-gpu-virgl.c index 60c78af06a4..d9e5b011049 100644 --- a/hw/display/virtio-gpu-virgl.c +++ b/hw/display/virtio-gpu-virgl.c @@ -607,6 +607,14 @@ static void virgl_cmd_submit_3d(VirtIOGPU *g, VIRTIO_GPU_FILL_CMD(cs); trace_virtio_gpu_cmd_ctx_submit(cs.hdr.ctx_id, cs.size); =20 + if (cs.size > VIRTIO_GPU_MAX_CMD_SUBMIT_SIZE) { + qemu_log_mask(LOG_GUEST_ERROR, + "%s: command buffer too large (%u)\n", + __func__, cs.size); + cmd->error =3D VIRTIO_GPU_RESP_ERR_INVALID_PARAMETER; + return; + } + buf =3D g_malloc(cs.size); s =3D iov_to_buf(cmd->elem.out_sg, cmd->elem.out_num, sizeof(cs), buf, cs.size); --=20 2.55.0