From nobody Sun Sep 14 20:21:19 2025 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 7F7C4C38142 for ; Thu, 19 Jan 2023 04:41:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229656AbjASElR (ORCPT ); Wed, 18 Jan 2023 23:41:17 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54776 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230161AbjASEkb (ORCPT ); Wed, 18 Jan 2023 23:40:31 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 20248457E2 for ; Wed, 18 Jan 2023 20:37:29 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1674102975; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Eek5YPddR+rdvDYmWL3WCwvTt/kh6fJNelSHfFXusYg=; b=d89wGSWqvQEBrDDRsk0a5ELPYCM/db16cQznQOCU00ym9zDzPunXE9ToV9nPrT/CYsS+5W LiVhrN1UhgF5YR7Xxrbb3cvks97GxQshleEpLLfrKaDh1fahVCIBauCp3MOD43Q3IK0QfC UNK9uY9qDvGPPh0WC6Op5VSY6s/a1VU= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-550-JseQALo8MkyN83fBd0phlQ-1; Wed, 18 Jan 2023 23:01:21 -0500 X-MC-Unique: JseQALo8MkyN83fBd0phlQ-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 657E52A5956F; Thu, 19 Jan 2023 04:01:21 +0000 (UTC) Received: from llong.com (unknown [10.22.8.15]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1C65751E5; Thu, 19 Jan 2023 04:01:21 +0000 (UTC) From: Waiman Long To: Catalin Marinas , Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Muchun Song , Waiman Long Subject: [RESEND PATCH v2 2/2] mm/kmemleak: Fix UAF bug in kmemleak_scan() Date: Wed, 18 Jan 2023 23:01:11 -0500 Message-Id: <20230119040111.350923-3-longman@redhat.com> In-Reply-To: <20230119040111.350923-1-longman@redhat.com> References: <20230119040111.350923-1-longman@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Commit 6edda04ccc7c ("mm/kmemleak: prevent soft lockup in first object iteration loop of kmemleak_scan()") fixes soft lockup problem in kmemleak_scan() by periodically doing a cond_resched(). It does take a reference of the current object before doing it. Unfortunately, if the object has been deleted from the object_list, the next object pointed to by its next pointer may no longer be valid after coming back from cond_resched(). This can result in use-after-free and other nasty problem. Fix this problem by adding a del_state flag into kmemleak_object structure to synchronize the object deletion process between kmemleak_cond_resched() and __remove_object() to make sure that the object remained in the object_list in the duration of the cond_resched() call. Fixes: 6edda04ccc7c ("mm/kmemleak: prevent soft lockup in first object iter= ation loop of kmemleak_scan()") Signed-off-by: Waiman Long Reviewed-by: Catalin Marinas --- mm/kmemleak.c | 35 +++++++++++++++++++++++++++++------ 1 file changed, 29 insertions(+), 6 deletions(-) diff --git a/mm/kmemleak.c b/mm/kmemleak.c index e7cb521236bf..0ece170fc9ef 100644 --- a/mm/kmemleak.c +++ b/mm/kmemleak.c @@ -13,11 +13,12 @@ * * The following locks and mutexes are used by kmemleak: * - * - kmemleak_lock (raw_spinlock_t): protects the object_list modification= s and - * accesses to the object_tree_root (or object_phys_tree_root). The - * object_list is the main list holding the metadata (struct kmemleak_ob= ject) - * for the allocated memory blocks. The object_tree_root and object_phys= _tree_root - * are red black trees used to look-up metadata based on a pointer to the + * - kmemleak_lock (raw_spinlock_t): protects the object_list as well as + * del_state modifications and accesses to the object_tree_root (or + * object_phys_tree_root). The object_list is the main list holding the + * metadata (struct kmemleak_object) for the allocated memory blocks. + * The object_tree_root and object_phys_tree_root are red + * black trees used to look-up metadata based on a pointer to the * corresponding memory block. The object_phys_tree_root is for objects * allocated with physical address. The kmemleak_object structures are * added to the object_list and object_tree_root (or object_phys_tree_ro= ot) @@ -147,6 +148,7 @@ struct kmemleak_object { struct rcu_head rcu; /* object_list lockless traversal */ /* object usage count; object freed when use_count =3D=3D 0 */ atomic_t use_count; + unsigned int del_state; /* deletion state */ unsigned long pointer; size_t size; /* pass surplus references to this pointer */ @@ -177,6 +179,11 @@ struct kmemleak_object { /* flag set for object allocated with physical address */ #define OBJECT_PHYS (1 << 4) =20 +/* set when __remove_object() called */ +#define DELSTATE_REMOVED (1 << 0) +/* set to temporarily prevent deletion from object_list */ +#define DELSTATE_NO_DELETE (1 << 1) + #define HEX_PREFIX " " /* number of bytes to print per line; must be 16 or 32 */ #define HEX_ROW_SIZE 16 @@ -567,7 +574,9 @@ static void __remove_object(struct kmemleak_object *obj= ect) rb_erase(&object->rb_node, object->flags & OBJECT_PHYS ? &object_phys_tree_root : &object_tree_root); - list_del_rcu(&object->object_list); + if (!(object->del_state & DELSTATE_NO_DELETE)) + list_del_rcu(&object->object_list); + object->del_state |=3D DELSTATE_REMOVED; } =20 /* @@ -633,6 +642,7 @@ static void __create_object(unsigned long ptr, size_t s= ize, object->count =3D 0; /* white color initially */ object->jiffies =3D jiffies; object->checksum =3D 0; + object->del_state =3D 0; =20 /* task information */ if (in_hardirq()) { @@ -1470,9 +1480,22 @@ static void kmemleak_cond_resched(struct kmemleak_ob= ject *object) if (!get_object(object)) return; /* Try next object */ =20 + raw_spin_lock_irq(&kmemleak_lock); + if (object->del_state & DELSTATE_REMOVED) + goto unlock_put; /* Object removed */ + object->del_state |=3D DELSTATE_NO_DELETE; + raw_spin_unlock_irq(&kmemleak_lock); + rcu_read_unlock(); cond_resched(); rcu_read_lock(); + + raw_spin_lock_irq(&kmemleak_lock); + if (object->del_state & DELSTATE_REMOVED) + list_del_rcu(&object->object_list); + object->del_state &=3D ~DELSTATE_NO_DELETE; +unlock_put: + raw_spin_unlock_irq(&kmemleak_lock); put_object(object); } =20 --=20 2.31.1