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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F400DC38159 for ; Fri, 20 Jan 2023 05:30:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229908AbjATFaG (ORCPT ); Fri, 20 Jan 2023 00:30:06 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35594 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230465AbjATF2y (ORCPT ); Fri, 20 Jan 2023 00:28:54 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 42A9A518E0 for ; Thu, 19 Jan 2023 21:23:56 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 0D84BB8274A for ; Thu, 19 Jan 2023 22:17:04 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A3982C433D2; Thu, 19 Jan 2023 22:17:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1674166622; bh=RusBCjSBotirrgrMmiXX30KLFkJJLcI2hhenc13d5fU=; h=Date:To:From:Subject:From; b=GLgSfLJnOVFdd6C87CZ1ivY5WxfGtETFdDNUuT2oobuzIENQqlf2260JKdcQc85Iv kwCSYatR8SPpX/Kuv+HjscLa69A0NUSi7CEDB4/4z9INI498GCmjwPPRnV0wwqqSk3 jx1mOPEIqNRc9IkXgCRzLfkZrGvKsN7Mo02QLdF8= Date: Thu, 19 Jan 2023 14:17:02 -0800 To: mm-commits@vger.kernel.org, songmuchun@bytedance.com, catalin.marinas@arm.com, longman@redhat.com, akpm@linux-foundation.org From: Andrew Morton Subject: + mm-kmemleak-simplify-kmemleak_cond_resched-usage.patch added to mm-unstable branch Message-Id: <20230119221702.A3982C433D2@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The patch titled Subject: mm/kmemleak: simplify kmemleak_cond_resched() usage has been added to the -mm mm-unstable branch. Its filename is mm-kmemleak-simplify-kmemleak_cond_resched-usage.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-kmemleak-simplify-kmemleak_cond_resched-usage.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Waiman Long Subject: mm/kmemleak: simplify kmemleak_cond_resched() usage Date: Wed, 18 Jan 2023 23:01:10 -0500 Patch series "mm/kmemleak: Simplify kmemleak_cond_resched() & fix UAF", v2. It was found that a KASAN use-after-free error was reported in the kmemleak_scan() function. After further examination, it is believe that even though a reference is taken from the current object, it does not prevent the object pointed to by the next pointer from going away after a cond_resched(). To fix that, additional flags are added to make sure that the current object won't be removed from the object_list during the duration of the cond_resched() to ensure the validity of the next pointer. While making the change, I also simplify the current usage of kmemleak_cond_resched() to make it easier to understand. This patch (of 2): The presence of a pinned argument and the 64k loop count make kmemleak_cond_resched() a bit more complex to read. The pinned argument is used only by first kmemleak_scan() loop. Simplify the usage of kmemleak_cond_resched() by removing the pinned argument and always do a get_object()/put_object() sequence. In addition, the 64k loop is removed by using need_resched() to decide if kmemleak_cond_resched() should be called. Link: https://lkml.kernel.org/r/20230119040111.350923-1-longman@redhat.com Link: https://lkml.kernel.org/r/20230119040111.350923-2-longman@redhat.com Signed-off-by: Waiman Long Reviewed-by: Catalin Marinas Cc: Muchun Song Signed-off-by: Andrew Morton --- --- a/mm/kmemleak.c~mm-kmemleak-simplify-kmemleak_cond_resched-usage +++ a/mm/kmemleak.c @@ -1472,22 +1472,17 @@ static void scan_gray_list(void) /* * Conditionally call resched() in an object iteration loop while making sure * that the given object won't go away without RCU read lock by performing a - * get_object() if !pinned. - * - * Return: false if can't do a cond_resched() due to get_object() failure - * true otherwise + * get_object() if necessaary. */ -static bool kmemleak_cond_resched(struct kmemleak_object *object, bool pinned) +static void kmemleak_cond_resched(struct kmemleak_object *object) { - if (!pinned && !get_object(object)) - return false; + if (!get_object(object)) + return; /* Try next object */ rcu_read_unlock(); cond_resched(); rcu_read_lock(); - if (!pinned) - put_object(object); - return true; + put_object(object); } /* @@ -1501,15 +1496,12 @@ static void kmemleak_scan(void) struct zone *zone; int __maybe_unused i; int new_leaks = 0; - int loop_cnt = 0; jiffies_last_scan = jiffies; /* prepare the kmemleak_object's */ rcu_read_lock(); list_for_each_entry_rcu(object, &object_list, object_list) { - bool obj_pinned = false; - raw_spin_lock_irq(&object->lock); #ifdef DEBUG /* @@ -1535,19 +1527,13 @@ static void kmemleak_scan(void) /* reset the reference count (whiten the object) */ object->count = 0; - if (color_gray(object) && get_object(object)) { + if (color_gray(object) && get_object(object)) list_add_tail(&object->gray_list, &gray_list); - obj_pinned = true; - } raw_spin_unlock_irq(&object->lock); - /* - * Do a cond_resched() every 64k objects to avoid soft lockup. - */ - if (!(++loop_cnt & 0xffff) && - !kmemleak_cond_resched(object, obj_pinned)) - loop_cnt--; /* Try again on next object */ + if (need_resched()) + kmemleak_cond_resched(object); } rcu_read_unlock(); @@ -1614,14 +1600,9 @@ static void kmemleak_scan(void) * scan and color them gray until the next scan. */ rcu_read_lock(); - loop_cnt = 0; list_for_each_entry_rcu(object, &object_list, object_list) { - /* - * Do a cond_resched() every 64k objects to avoid soft lockup. - */ - if (!(++loop_cnt & 0xffff) && - !kmemleak_cond_resched(object, false)) - loop_cnt--; /* Try again on next object */ + if (need_resched()) + kmemleak_cond_resched(object); /* * This is racy but we can save the overhead of lock/unlock @@ -1656,14 +1637,9 @@ static void kmemleak_scan(void) * Scanning result reporting. */ rcu_read_lock(); - loop_cnt = 0; list_for_each_entry_rcu(object, &object_list, object_list) { - /* - * Do a cond_resched() every 64k objects to avoid soft lockup. - */ - if (!(++loop_cnt & 0xffff) && - !kmemleak_cond_resched(object, false)) - loop_cnt--; /* Try again on next object */ + if (need_resched()) + kmemleak_cond_resched(object); /* * This is racy but we can save the overhead of lock/unlock _ Patches currently in -mm which might be from longman@redhat.com are mm-kmemleak-simplify-kmemleak_cond_resched-usage.patch mm-kmemleak-fix-uaf-bug-in-kmemleak_scan.patch