From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 28F246FA0 for ; Mon, 16 Jan 2023 16:37:28 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A2A68C433F0; Mon, 16 Jan 2023 16:37:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1673887048; bh=Cr3RkvpqM8xdSvd2CeNYGesZsm0JkZPODMzCZtruBWE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bZRTfQvlPmAzI04QzERuKX4W5MFNoy6jCu0zcp96PIdDqZ3uxphFE610UTp1x3ljK 1t5oMZRiR9klpTSvnUyg1UbqVdXcz6GbFkSnhFkQOdR9Wom8m7BQ7k9GVYaFd80/29 PPP3mVxVuWAU9XBYLIuWTSX4H1nRtOqw73mN57C4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Rob Clark , Chia-I Wu , Dmitry Osipenko , Sasha Levin Subject: [PATCH 5.4 646/658] drm/virtio: Fix GEM handle creation UAF Date: Mon, 16 Jan 2023 16:52:14 +0100 Message-Id: <20230116154939.040980498@linuxfoundation.org> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230116154909.645460653@linuxfoundation.org> References: <20230116154909.645460653@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Rob Clark [ Upstream commit 52531258318ed59a2dc5a43df2eaf0eb1d65438e ] Userspace can guess the handle value and try to race GEM object creation with handle close, resulting in a use-after-free if we dereference the object after dropping the handle's reference. For that reason, dropping the handle's reference must be done *after* we are done dereferencing the object. Signed-off-by: Rob Clark Reviewed-by: Chia-I Wu Fixes: 62fb7a5e1096 ("virtio-gpu: add 3d/virgl support") Cc: stable@vger.kernel.org Signed-off-by: Dmitry Osipenko Link: https://patchwork.freedesktop.org/patch/msgid/20221216233355.542197-2-robdclark@gmail.com Signed-off-by: Sasha Levin --- drivers/gpu/drm/virtio/virtgpu_ioctl.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c index 0a88ef11b9d3..5ae132e37277 100644 --- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c +++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c @@ -327,10 +327,18 @@ static int virtio_gpu_resource_create_ioctl(struct drm_device *dev, void *data, drm_gem_object_release(obj); return ret; } - drm_gem_object_put_unlocked(obj); rc->res_handle = qobj->hw_res_handle; /* similiar to a VM address */ rc->bo_handle = handle; + + /* + * The handle owns the reference now. But we must drop our + * remaining reference *after* we no longer need to dereference + * the obj. Otherwise userspace could guess the handle and + * race closing it from another thread. + */ + drm_gem_object_put_unlocked(obj); + return 0; } -- 2.35.1