Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753954AbcCAVpA (ORCPT ); Tue, 1 Mar 2016 16:45:00 -0500 Received: from mga02.intel.com ([134.134.136.20]:26717 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752184AbcCAVo5 (ORCPT ); Tue, 1 Mar 2016 16:44:57 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.22,524,1449561600"; d="scan'208";a="756257518" Subject: [PATCH] list: kill list_force_poison() From: Dan Williams To: akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Ross Zwisler , Eryu Guan , xfs@oss.sgi.com Date: Tue, 01 Mar 2016 13:44:32 -0800 Message-ID: <20160301214432.4473.76919.stgit@dwillia2-desk3.amr.corp.intel.com> User-Agent: StGit/0.17.1-9-g687f MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3986 Lines: 109 Given we have uninitialized list_heads being passed to list_add() it will always be the case that those uninitialized values randomly trigger the poison value. Especially since a list_add() operation will seed the stack with the poison value for later stack allocations to trip over. For example, see these two false positive reports: list_add attempted on force-poisoned entry WARNING: at lib/list_debug.c:34 [..] NIP [c00000000043c390] __list_add+0xb0/0x150 LR [c00000000043c38c] __list_add+0xac/0x150 Call Trace: [c000000fb5fc3320] [c00000000043c38c] __list_add+0xac/0x150 (unreliable) [c000000fb5fc33a0] [c00000000081b454] __down+0x4c/0xf8 [c000000fb5fc3410] [c00000000010b6f8] down+0x68/0x70 [c000000fb5fc3450] [d0000000201ebf4c] xfs_buf_lock+0x4c/0x150 [xfs] list_add attempted on force-poisoned entry(0000000000000500), new->next == d0000000059ecdb0, new->prev == 0000000000000500 WARNING: at lib/list_debug.c:33 [..] NIP [c00000000042db78] __list_add+0xa8/0x140 LR [c00000000042db74] __list_add+0xa4/0x140 Call Trace: [c0000004c749f620] [c00000000042db74] __list_add+0xa4/0x140 (unreliable) [c0000004c749f6b0] [c0000000008010ec] rwsem_down_read_failed+0x6c/0x1a0 [c0000004c749f760] [c000000000800828] down_read+0x58/0x60 [c0000004c749f7e0] [d000000005a1a6bc] xfs_log_commit_cil+0x7c/0x600 [xfs] Reported-by: Eryu Guan Cc: Ross Zwisler Cc: Fixes: commit 5c2c2587b132 ("mm, dax, pmem: introduce {get|put}_dev_pagemap() for dax-gup") Signed-off-by: Dan Williams --- include/linux/list.h | 11 ----------- kernel/memremap.c | 9 +++++++-- lib/list_debug.c | 9 --------- 3 files changed, 7 insertions(+), 22 deletions(-) diff --git a/include/linux/list.h b/include/linux/list.h index 30cf4200ab40..5356f4d661a7 100644 --- a/include/linux/list.h +++ b/include/linux/list.h @@ -113,17 +113,6 @@ extern void __list_del_entry(struct list_head *entry); extern void list_del(struct list_head *entry); #endif -#ifdef CONFIG_DEBUG_LIST -/* - * See devm_memremap_pages() which wants DEBUG_LIST=y to assert if one - * of the pages it allocates is ever passed to list_add() - */ -extern void list_force_poison(struct list_head *entry); -#else -/* fallback to the less strict LIST_POISON* definitions */ -#define list_force_poison list_del -#endif - /** * list_replace - replace old entry by new one * @old : the element to be replaced diff --git a/kernel/memremap.c b/kernel/memremap.c index b981a7b023f0..778191e3e887 100644 --- a/kernel/memremap.c +++ b/kernel/memremap.c @@ -351,8 +351,13 @@ void *devm_memremap_pages(struct device *dev, struct resource *res, for_each_device_pfn(pfn, page_map) { struct page *page = pfn_to_page(pfn); - /* ZONE_DEVICE pages must never appear on a slab lru */ - list_force_poison(&page->lru); + /* + * ZONE_DEVICE pages union ->lru with a ->pgmap back + * pointer. It is a bug if a ZONE_DEVICE page is ever + * freed or placed on a driver-private list. Seed the + * storage with LIST_POISON* values. + */ + list_del(&page->lru); page->pgmap = pgmap; } devres_add(dev, page_map); diff --git a/lib/list_debug.c b/lib/list_debug.c index 3345a089ef7b..3859bf63561c 100644 --- a/lib/list_debug.c +++ b/lib/list_debug.c @@ -12,13 +12,6 @@ #include #include -static struct list_head force_poison; -void list_force_poison(struct list_head *entry) -{ - entry->next = &force_poison; - entry->prev = &force_poison; -} - /* * Insert a new entry between two known consecutive entries. * @@ -30,8 +23,6 @@ void __list_add(struct list_head *new, struct list_head *prev, struct list_head *next) { - WARN(new->next == &force_poison || new->prev == &force_poison, - "list_add attempted on force-poisoned entry\n"); WARN(next->prev != prev, "list_add corruption. next->prev should be " "prev (%p), but was %p. (next=%p).\n",