From patchwork Mon Sep 21 16:28:00 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "gregkh@linuxfoundation.org" X-Patchwork-Id: 263552 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=-11.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 EA3D6C43465 for ; Mon, 21 Sep 2020 17:05:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A99EA2073A for ; Mon, 21 Sep 2020 17:05:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600707941; bh=t5qeN+stjGPNG6sn8aIddhIRBpgtz8iDOmvyk88XO1U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=kG9ubBtxWVdtNNZBQ7llalpzyhVvQ8weCK1VuMqzdzWINOHquaSRc0fA0a89dG4Ps K7jOBJtcDsgekd1LPK0dTis28rWES89JAcA4Tp4LNv6ebe6QSiPjwO247IoYwlaNhG ZB1Z9WVw6UbwsVKUBOuSV31wCGS+nNZtPbLCXRig= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728649AbgIUQdm (ORCPT ); Mon, 21 Sep 2020 12:33:42 -0400 Received: from mail.kernel.org ([198.145.29.99]:59920 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728113AbgIUQdh (ORCPT ); Mon, 21 Sep 2020 12:33:37 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 635E823976; Mon, 21 Sep 2020 16:33:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600706016; bh=t5qeN+stjGPNG6sn8aIddhIRBpgtz8iDOmvyk88XO1U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kXz//4wJLcrE68vEhFkCzJxF9P6MBJhDpk0GJlNJ545z1q0Sp6pKEGAh0A4ps1inM 276gbhPYBTTYoKlVOjtBE1UoS5Ik3TdKuNNjjCT4R+doOKVM6u9LXuqec5Xtw4ouL4 9umQRTfPaUj29051HWvk05y5von/ldtst7L3IjKw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Alan Stern , Quentin Perret Subject: [PATCH 4.4 44/46] ehci-hcd: Move include to keep CRC stable Date: Mon, 21 Sep 2020 18:28:00 +0200 Message-Id: <20200921162035.296458681@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200921162033.346434578@linuxfoundation.org> References: <20200921162033.346434578@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Quentin Perret commit 29231826f3bd65500118c473fccf31c0cf14dbc0 upstream. The CRC calculation done by genksyms is triggered when the parser hits EXPORT_SYMBOL*() macros. At this point, genksyms recursively expands the types of the function parameters, and uses that as the input for the CRC calculation. In the case of forward-declared structs, the type expands to 'UNKNOWN'. Following this, it appears that the result of the expansion of each type is cached somewhere, and seems to be re-used when/if the same type is seen again for another exported symbol in the same C file. Unfortunately, this can cause CRC 'stability' issues when a struct definition becomes visible in the middle of a C file. For example, let's assume code with the following pattern: struct foo; int bar(struct foo *arg) { /* Do work ... */ } EXPORT_SYMBOL_GPL(bar); /* This contains struct foo's definition */ #include "foo.h" int baz(struct foo *arg) { /* Do more work ... */ } EXPORT_SYMBOL_GPL(baz); Here, baz's CRC will be computed using the expansion of struct foo that was cached after bar's CRC calculation ('UNKOWN' here). But if EXPORT_SYMBOL_GPL(bar) is removed from the file (because of e.g. symbol trimming using CONFIG_TRIM_UNUSED_KSYMS), struct foo will be expanded late, during baz's CRC calculation, which now has visibility over the full struct definition, hence resulting in a different CRC for baz. The proper fix for this certainly is in genksyms, but that will take me some time to get right. In the meantime, we have seen one occurrence of this in the ehci-hcd code which hits this problem because of the way it includes C files halfway through the code together with an unlucky mix of symbol trimming. In order to workaround this, move the include done in ehci-hub.c early in ehci-hcd.c, hence making sure the struct definitions are visible to the entire file. This improves CRC stability of the ehci-hcd exports even when symbol trimming is enabled. Acked-by: Alan Stern Cc: stable Signed-off-by: Quentin Perret Link: https://lore.kernel.org/r/20200916171825.3228122-1-qperret@google.com Signed-off-by: Greg Kroah-Hartman --- drivers/usb/host/ehci-hcd.c | 1 + drivers/usb/host/ehci-hub.c | 1 - 2 files changed, 1 insertion(+), 1 deletion(-) --- a/drivers/usb/host/ehci-hcd.c +++ b/drivers/usb/host/ehci-hcd.c @@ -35,6 +35,7 @@ #include #include #include +#include #include #include #include --- a/drivers/usb/host/ehci-hub.c +++ b/drivers/usb/host/ehci-hub.c @@ -27,7 +27,6 @@ */ /*-------------------------------------------------------------------------*/ -#include #define PORT_WAKE_BITS (PORT_WKOC_E|PORT_WKDISC_E|PORT_WKCONN_E)