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=-9.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 371E0C8300A for ; Tue, 27 Oct 2020 15:27:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E816422281 for ; Tue, 27 Oct 2020 15:27:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603812423; bh=BlNuMz80fJodoi30bhacJssZCwBYomKXWyXprstirBc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=W5fT9a5vD9CuHiDRTyV/FmhMqE26GyKK8xG5q34Nvyom1K89xbTbkSXKyvczb1Hec xoquExtQ4h5Dz7cHT3+F2GSIERqlHhtuLdh0rrncQJLoKdWdMtrBZ7xXkhjV+QNvG3 7beO+zP01HTCh6vz6u535KsO9XWqggWrhoSA8T6U= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1797013AbgJ0PVH (ORCPT ); Tue, 27 Oct 2020 11:21:07 -0400 Received: from mail.kernel.org ([198.145.29.99]:55728 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758266AbgJ0PSa (ORCPT ); Tue, 27 Oct 2020 11:18:30 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2B3A22064B; Tue, 27 Oct 2020 15:18:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603811909; bh=BlNuMz80fJodoi30bhacJssZCwBYomKXWyXprstirBc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SH2J7YQ4M22MjANoAjMKD3VQ/DtSUV8iFxkJyO3gi87cC7ROCngPHjtPVwkYRSl1p IqxpWUZ+XVfaqWfrUMN2J/4wGhOsQ9c8392ijcMl3BdDzst2aSm+M2f1dQ64rIny84 enDt5qMby2PyTpC9I5sIUsGzVSpV63DT3RZIF+rc= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Todd Kjos Subject: [PATCH 5.9 025/757] binder: fix UAF when releasing todo list Date: Tue, 27 Oct 2020 14:44:35 +0100 Message-Id: <20201027135451.703397036@linuxfoundation.org> X-Mailer: git-send-email 2.29.1 In-Reply-To: <20201027135450.497324313@linuxfoundation.org> References: <20201027135450.497324313@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Todd Kjos commit f3277cbfba763cd2826396521b9296de67cf1bbc upstream. When releasing a thread todo list when tearing down a binder_proc, the following race was possible which could result in a use-after-free: 1. Thread 1: enter binder_release_work from binder_thread_release 2. Thread 2: binder_update_ref_for_handle() -> binder_dec_node_ilocked() 3. Thread 2: dec nodeA --> 0 (will free node) 4. Thread 1: ACQ inner_proc_lock 5. Thread 2: block on inner_proc_lock 6. Thread 1: dequeue work (BINDER_WORK_NODE, part of nodeA) 7. Thread 1: REL inner_proc_lock 8. Thread 2: ACQ inner_proc_lock 9. Thread 2: todo list cleanup, but work was already dequeued 10. Thread 2: free node 11. Thread 2: REL inner_proc_lock 12. Thread 1: deref w->type (UAF) The problem was that for a BINDER_WORK_NODE, the binder_work element must not be accessed after releasing the inner_proc_lock while processing the todo list elements since another thread might be handling a deref on the node containing the binder_work element leading to the node being freed. Signed-off-by: Todd Kjos Link: https://lore.kernel.org/r/20201009232455.4054810-1-tkjos@google.com Cc: # 4.14, 4.19, 5.4, 5.8 Signed-off-by: Greg Kroah-Hartman --- drivers/android/binder.c | 35 ++++++++++------------------------- 1 file changed, 10 insertions(+), 25 deletions(-) --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -223,7 +223,7 @@ static struct binder_transaction_log_ent struct binder_work { struct list_head entry; - enum { + enum binder_work_type { BINDER_WORK_TRANSACTION = 1, BINDER_WORK_TRANSACTION_COMPLETE, BINDER_WORK_RETURN_ERROR, @@ -885,27 +885,6 @@ static struct binder_work *binder_dequeu return w; } -/** - * binder_dequeue_work_head() - Dequeues the item at head of list - * @proc: binder_proc associated with list - * @list: list to dequeue head - * - * Removes the head of the list if there are items on the list - * - * Return: pointer dequeued binder_work, NULL if list was empty - */ -static struct binder_work *binder_dequeue_work_head( - struct binder_proc *proc, - struct list_head *list) -{ - struct binder_work *w; - - binder_inner_proc_lock(proc); - w = binder_dequeue_work_head_ilocked(list); - binder_inner_proc_unlock(proc); - return w; -} - static void binder_defer_work(struct binder_proc *proc, enum binder_deferred_state defer); static void binder_free_thread(struct binder_thread *thread); @@ -4587,13 +4566,17 @@ static void binder_release_work(struct b struct list_head *list) { struct binder_work *w; + enum binder_work_type wtype; while (1) { - w = binder_dequeue_work_head(proc, list); + binder_inner_proc_lock(proc); + w = binder_dequeue_work_head_ilocked(list); + wtype = w ? w->type : 0; + binder_inner_proc_unlock(proc); if (!w) return; - switch (w->type) { + switch (wtype) { case BINDER_WORK_TRANSACTION: { struct binder_transaction *t; @@ -4627,9 +4610,11 @@ static void binder_release_work(struct b kfree(death); binder_stats_deleted(BINDER_STAT_DEATH); } break; + case BINDER_WORK_NODE: + break; default: pr_err("unexpected work type, %d, not freed\n", - w->type); + wtype); break; } }