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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, 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 754EEC10F13 for ; Tue, 16 Apr 2019 04:02:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 47F852075B for ; Tue, 16 Apr 2019 04:02:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726000AbfDPECm (ORCPT ); Tue, 16 Apr 2019 00:02:42 -0400 Received: from www.osadl.org ([62.245.132.105]:49136 "EHLO www.osadl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725648AbfDPECm (ORCPT ); Tue, 16 Apr 2019 00:02:42 -0400 Received: from debian01.hofrr.at (178.115.242.59.static.drei.at [178.115.242.59]) by www.osadl.org (8.13.8/8.13.8/OSADL-2007092901) with ESMTP id x3G427M9032015; Tue, 16 Apr 2019 06:02:07 +0200 From: Nicholas Mc Guire To: Jason Cooper Cc: Andrew Lunn , Gregory Clement , Sebastian Hesselbarth , Russell King , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Nicholas Mc Guire Subject: [PATCH V2] ARM: mvebu: at least report the kzalloc failure Date: Tue, 16 Apr 2019 05:56:31 +0200 Message-Id: <1555386991-8855-1-git-send-email-hofrat@osadl.org> X-Mailer: git-send-email 2.1.4 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Although it is very unlikely that the allocation during init would fail any such failure should point to the original cause to allow easier understanding of the ensuing null-pointer dereference splat. Signed-off-by: Nicholas Mc Guire --- Problem located with experimental coccinelle script V2: Russell King pointed out that the use of WARN_ON() would result in a stack trace followed by the oops due to dereferencing of the NULL pointer and so make it even less likely that users would uncover the actual cause - so drop the WARN_ON() and use a short pr_err() message that points to the oops cause directly. Note that this will trigger a checkpatch WARNING "WARNING: Possible unnecessary 'out of memory' message" but comparing the oops with an without the one-line pr_err I would argue that it makes sense to include it: [ 8061.514840] shared page allocation failure in hello_init() [ 8113.563239] BUG: unable to handle kernel NULL pointer dereference at 0000000000000000 [ 8113.563250] #PF error: [WRITE] [ 8113.563255] PGD 8000000129993067 P4D 8000000129993067 PUD 129992067 PMD 0 [ 8113.563267] Oops: 0002 [#1] SMP PTI [ 8113.563276] CPU: 2 PID: 2656 Comm: bash Tainted: G W O 5.0.0-rc3livepatchtest-next-20190123+ #4 [ 8113.563280] Hardware name: Quanta TWH/TWH, BIOS QU221 10/14/2011 [ 8113.563292] RIP: 0010:foo_store+0x3a/0x90 [hello_chardev] ... Patch was compile-tested: mvebu_v7_defconfig (implies MACH_MVEBU_ANY=y) (with some unrelated sparse warnings about missing syscalls) Patch is against 5.1-rc4 (localversion-next is 20190415) arch/arm/mach-mvebu/board-v7.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/arm/mach-mvebu/board-v7.c b/arch/arm/mach-mvebu/board-v7.c index 0b10acd..df84cb6 100644 --- a/arch/arm/mach-mvebu/board-v7.c +++ b/arch/arm/mach-mvebu/board-v7.c @@ -128,6 +128,9 @@ static void __init i2c_quirk(void) struct property *new_compat; new_compat = kzalloc(sizeof(*new_compat), GFP_KERNEL); + if (!new_compat) + pr_err("new_compat allocation failure in %s()\n", + __func__); new_compat->name = kstrdup("compatible", GFP_KERNEL); new_compat->length = sizeof("marvell,mv78230-a0-i2c"); -- 2.1.4