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=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 EF426C432C3 for ; Wed, 20 Nov 2019 05:47:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C87472244A for ; Wed, 20 Nov 2019 05:47:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=arista.com header.i=@arista.com header.b="DSly446P" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727008AbfKTFrb (ORCPT ); Wed, 20 Nov 2019 00:47:31 -0500 Received: from mx.aristanetworks.com ([162.210.129.12]:36754 "EHLO smtp.aristanetworks.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725554AbfKTFra (ORCPT ); Wed, 20 Nov 2019 00:47:30 -0500 Received: from us180.sjc.aristanetworks.com (us180.sjc.aristanetworks.com [172.25.230.4]) by smtp.aristanetworks.com (Postfix) with ESMTP id 2227D401873; Tue, 19 Nov 2019 21:47:28 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=arista.com; s=Arista-A; t=1574228848; bh=HnAblu8XteAJ3r4y2QIMZ1i5loQSHWwegqcw/ObDqQs=; h=Date:To:Subject:From:From; b=DSly446P+JlKIJZJNcFcN/f+FLbZrABiGSn8rcfarxhAJme1D4ay1JWR5LAgzMoWF DNCEoApbSPWaq8ldEGGJJ7Sef8PyN94IhSZK9ApZ3b5OqadBB52MD/uom875SfNrbW V7lttkKFWevm1306y87HxaUDy7QEBfsAjWV4yBndXCp/mXSg4nabdrSoNLs2uvZ6Qb T8lIXXWUUIgmT8SODVAubKrx7L5QQqGokAg821MtcGMxubjIfA4L7HFT2qUPkGxLq+ iVDuuyBk5s8qR+quqQ2Ub1bW2fGFIgKTP4WH6ElBQSdg2Sm7wHU03MZ7HcU0S+Qc6U BG6k984r5vZxA== Received: by us180.sjc.aristanetworks.com (Postfix, from userid 10189) id 0979695C0FE4; Tue, 19 Nov 2019 21:47:27 -0800 (PST) Date: Tue, 19 Nov 2019 21:47:27 -0800 To: lenb@kernel.org, rjw@rjwysocki.net, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, fruggeri@arista.com Subject: [PATCH] ACPI: only free map once in osl.c User-Agent: Heirloom mailx 12.5 7/5/10 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-Id: <20191120054728.0979695C0FE4@us180.sjc.aristanetworks.com> From: fruggeri@arista.com (Francesco Ruggeri) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org acpi_os_map_cleanup checks map->refcount outside of acpi_ioremap_lock before freeing the map. This creates a race condition the can result in the map being freed more than once. A panic can be caused by running for ((i=0; i<10; i++)) do for ((j=0; j<100000; j++)) do cat /sys/firmware/acpi/tables/data/BERT >/dev/null done & done This patch makes sure that only the process that drops the reference to 0 does the freeing. Fixes: b7c1fadd6c2e ("ACPI: Do not use krefs under a mutex in osl.c") Signed-off-by: Francesco Ruggeri --- drivers/acpi/osl.c | 28 +++++++++++++++++----------- 1 file changed, 17 insertions(+), 11 deletions(-) diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c index a2e844a8e9ed..41168c027a5a 100644 --- a/drivers/acpi/osl.c +++ b/drivers/acpi/osl.c @@ -374,19 +374,21 @@ void *__ref acpi_os_map_memory(acpi_physical_address phys, acpi_size size) } EXPORT_SYMBOL_GPL(acpi_os_map_memory); -static void acpi_os_drop_map_ref(struct acpi_ioremap *map) +/* Must be called with mutex_lock(&acpi_ioremap_lock) */ +static unsigned long acpi_os_drop_map_ref(struct acpi_ioremap *map) { - if (!--map->refcount) + unsigned long refcount = --map->refcount; + + if (!refcount) list_del_rcu(&map->list); + return refcount; } static void acpi_os_map_cleanup(struct acpi_ioremap *map) { - if (!map->refcount) { - synchronize_rcu_expedited(); - acpi_unmap(map->phys, map->virt); - kfree(map); - } + synchronize_rcu_expedited(); + acpi_unmap(map->phys, map->virt); + kfree(map); } /** @@ -406,6 +408,7 @@ static void acpi_os_map_cleanup(struct acpi_ioremap *map) void __ref acpi_os_unmap_iomem(void __iomem *virt, acpi_size size) { struct acpi_ioremap *map; + unsigned long refcount; if (!acpi_permanent_mmap) { __acpi_unmap_table(virt, size); @@ -419,10 +422,11 @@ void __ref acpi_os_unmap_iomem(void __iomem *virt, acpi_size size) WARN(true, PREFIX "%s: bad address %p\n", __func__, virt); return; } - acpi_os_drop_map_ref(map); + refcount = acpi_os_drop_map_ref(map); mutex_unlock(&acpi_ioremap_lock); - acpi_os_map_cleanup(map); + if (!refcount) + acpi_os_map_cleanup(map); } EXPORT_SYMBOL_GPL(acpi_os_unmap_iomem); @@ -457,6 +461,7 @@ void acpi_os_unmap_generic_address(struct acpi_generic_address *gas) { u64 addr; struct acpi_ioremap *map; + unsigned long refcount; if (gas->space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY) return; @@ -472,10 +477,11 @@ void acpi_os_unmap_generic_address(struct acpi_generic_address *gas) mutex_unlock(&acpi_ioremap_lock); return; } - acpi_os_drop_map_ref(map); + refcount = acpi_os_drop_map_ref(map); mutex_unlock(&acpi_ioremap_lock); - acpi_os_map_cleanup(map); + if (!refcount) + acpi_os_map_cleanup(map); } EXPORT_SYMBOL(acpi_os_unmap_generic_address); -- 2.19.1