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 X-Spam-Level: X-Spam-Status: No, score=-9.7 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C30EBC43441 for ; Wed, 14 Nov 2018 22:27:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 872FA20868 for ; Wed, 14 Nov 2018 22:27:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="Xx4QDobf" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 872FA20868 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389470AbeKOIcj (ORCPT ); Thu, 15 Nov 2018 03:32:39 -0500 Received: from mail.kernel.org ([198.145.29.99]:39396 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388803AbeKOIci (ORCPT ); Thu, 15 Nov 2018 03:32:38 -0500 Received: from ebiggers.mtv.corp.google.com (unknown [104.132.1.85]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id AED582243E; Wed, 14 Nov 2018 21:55:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1542232523; bh=OduJZ9R4wmCmaBxmHLPNRLiEHmmTlTEyLuPRaDRtCRo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Xx4QDobf7tdgquyHkJUHNggzvyTd8a9t3fppnN3z9ukhvL6SYsGJk+10Kh6nGjX/j uRcx20zErH0XK03DA00Gjwst093VUQz3IRIDeRb10WrdN2To6w1YH70nBwyfPYerKy kGJKPMJrYbmPCBPWQBk3WhK94msislsvWiY0WEXA= From: Eric Biggers To: David Herrmann , Jiri Kosina , Benjamin Tissoires , linux-input@vger.kernel.org Cc: linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, Dmitry Vyukov , Dmitry Torokhov , syzbot+72473edc9bf4eb1c6556@syzkaller.appspotmail.com, stable@vger.kernel.org, Jann Horn , Andy Lutomirski Subject: [PATCH v2] HID: uhid: forbid UHID_CREATE under KERNEL_DS or elevated privileges Date: Wed, 14 Nov 2018 13:55:09 -0800 Message-Id: <20181114215509.163600-1-ebiggers@kernel.org> X-Mailer: git-send-email 2.19.1.930.g4563a0d9d0-goog In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Eric Biggers When a UHID_CREATE command is written to the uhid char device, a copy_from_user() is done from a user pointer embedded in the command. When the address limit is KERNEL_DS, e.g. as is the case during sys_sendfile(), this can read from kernel memory. Alternatively, information can be leaked from a setuid binary that is tricked to write to the file descriptor. Therefore, forbid UHID_CREATE in these cases. No other commands in uhid_char_write() are affected by this bug and UHID_CREATE is marked as "obsolete", so apply the restriction to UHID_CREATE only rather than to uhid_char_write() entirely. Thanks to Dmitry Vyukov for adding uhid definitions to syzkaller and to Jann Horn for commit 9da3f2b740544 ("x86/fault: BUG() when uaccess helpers fault on kernel addresses"), allowing this bug to be found. Reported-by: syzbot+72473edc9bf4eb1c6556@syzkaller.appspotmail.com Fixes: d365c6cfd337 ("HID: uhid: add UHID_CREATE and UHID_DESTROY events") Cc: # v3.6+ Cc: Jann Horn Cc: Andy Lutomirski Signed-off-by: Eric Biggers --- drivers/hid/uhid.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/drivers/hid/uhid.c b/drivers/hid/uhid.c index 3c55073136064..051639c09f728 100644 --- a/drivers/hid/uhid.c +++ b/drivers/hid/uhid.c @@ -12,6 +12,7 @@ #include #include +#include #include #include #include @@ -722,6 +723,17 @@ static ssize_t uhid_char_write(struct file *file, const char __user *buffer, switch (uhid->input_buf.type) { case UHID_CREATE: + /* + * 'struct uhid_create_req' contains a __user pointer which is + * copied from, so it's unsafe to allow this with elevated + * privileges (e.g. from a setuid binary) or via kernel_write(). + */ + if (file->f_cred != current_cred() || uaccess_kernel()) { + pr_err_once("UHID_CREATE from different security context by process %d (%s), this is not allowed.\n", + task_tgid_vnr(current), current->comm); + ret = -EACCES; + goto unlock; + } ret = uhid_dev_create(uhid, &uhid->input_buf); break; case UHID_CREATE2: -- 2.19.1.930.g4563a0d9d0-goog