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=-6.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED 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 8E099C43441 for ; Thu, 15 Nov 2018 12:10:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 485B62245E for ; Thu, 15 Nov 2018 12:10:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="rm9ed8Ep" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 485B62245E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com 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 S2388012AbeKOWRm (ORCPT ); Thu, 15 Nov 2018 17:17:42 -0500 Received: from mail-it1-f196.google.com ([209.85.166.196]:35588 "EHLO mail-it1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728859AbeKOWRm (ORCPT ); Thu, 15 Nov 2018 17:17:42 -0500 Received: by mail-it1-f196.google.com with SMTP id v11so28908818itj.0; Thu, 15 Nov 2018 04:10:06 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=is3h91peBzNy9h+Q6qm60zHf7MaxLumfMUHhTejcg/s=; b=rm9ed8Ept0t8NH3vLefqOTD4O0S65Ld/rcmZLlUQ0FecS9eGHtBi+8i0lldI2L4y5z AD9GtGSdXcRRQS0LoWWeG1jcyjrX9lDvE5FgJygDxrBnRbm9u5r6N9AJDjY/0U1spHgh HHZJcMEm81cw8SOXb7nJaDUHlFGbp6pw2d5QRq2C1XlEvp+LRq5FT9B3I7yLXPbcxee7 qbiO5PTj7+nNGrFGFjVFpu7G8UOSVqdpuJdKUXsip5YbdhVjit/tjkU8qbQ981s/bqWx ZgLCvQ8/umfEvYq9xj9HcMLOxA4Ee6C477FCOH+zu6BIMk6dtQR+s0HmELLSVNCzvQPc fdtw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=is3h91peBzNy9h+Q6qm60zHf7MaxLumfMUHhTejcg/s=; b=lYYUqYU8HffDLTsr3nMHpgw4ylUg1RFQ0nuPaG3vx+onMfBMagaJSK/SS16Mb4UrOx NuAZ9uQCzV2kOMr5X6TxhOF/ralrWXnTx3mW5/5SX4MntO8pqD1hpKCLrvVIQNgS8NXZ GEaUCxqHgDA9EUVulSytQmHhRDJisDW8v5yL/Ps6t3x0RnWdBr0GfNNYIDJXWiFcznoW LZ6pPmBev8w/YAJuYq6DiVAwH0Qp5k8OZpVid33fNPet4pjWxnhDQeRhECFcMnW1JslJ Fl8SHQ5vIZC4hFqog9CJF2Ze2dmawcpcN6OlhmKjUYnmdJWBmaImaYcIfdBmSw0H1RiC pw1A== X-Gm-Message-State: AGRZ1gIXAmQ8BlvfK6WkDw/7px47w6Fykd+TvgQLmR1mD1jPzZnDXm0j eyztvFAWOGNP6lkSFKgOyKOvca+QOolwKHueFn0= X-Google-Smtp-Source: AJdET5cUSj/GQLaICf7CR/B7mrpWWMqdLdQgrglEH656dk5xQSn/gXa3tGmdmCLg+IdiK6qQvgzNq+CUUqLsyH2KFCw= X-Received: by 2002:a24:d983:: with SMTP id p125-v6mr5459737itg.97.1542283806377; Thu, 15 Nov 2018 04:10:06 -0800 (PST) MIME-Version: 1.0 References: <20181114215509.163600-1-ebiggers@kernel.org> In-Reply-To: <20181114215509.163600-1-ebiggers@kernel.org> From: David Herrmann Date: Thu, 15 Nov 2018 13:09:55 +0100 Message-ID: Subject: Re: [PATCH v2] HID: uhid: forbid UHID_CREATE under KERNEL_DS or elevated privileges To: ebiggers@kernel.org Cc: Jiri Kosina , Benjamin Tissoires , "open list:HID CORE LAYER" , linux-kernel , syzkaller-bugs@googlegroups.com, Dmitry Vyukov , Dmitry Torokhov , syzbot+72473edc9bf4eb1c6556@syzkaller.appspotmail.com, stable , jannh@google.com, Andy Lutomirski Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi On Wed, Nov 14, 2018 at 10:55 PM Eric Biggers wrote: > 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()) { I think `uaccess_kernel()` would be enough. UHID does not check any credentials. If you believe this should be there nevertheless, feel free to keep it. Either way: Acked-by: David Herrmann Thanks David > + 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 >