From patchwork Tue Oct 27 13:47:44 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 313034 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=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 7B398C5DF9D for ; Tue, 27 Oct 2020 14:11:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4991922284 for ; Tue, 27 Oct 2020 14:11:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603807891; bh=zjaBRscC7qVQbRzhIwyqC7x9Tnm0gA4Qif+GoJV5aHQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=gh7qr5bqgkOtgm2QRK6OnA/S+Fqh3tvrqQnxnEF2PT0BRvU/jCZb9wltJGYRl2TZC BzIxUq9TTE06GjzQOb7Wp1hMuqO2Pshfyy8G8m5xdldoH3pQveAhKGlXFJuW8Ml+Y/ W/CGEonNy8W65DHq6MKPZYO7Tm9Wjgi+72+SWcHQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756113AbgJ0OLX (ORCPT ); Tue, 27 Oct 2020 10:11:23 -0400 Received: from mail.kernel.org ([198.145.29.99]:58958 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2900872AbgJ0OJo (ORCPT ); Tue, 27 Oct 2020 10:09:44 -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 3697422202; Tue, 27 Oct 2020 14:09:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603807783; bh=zjaBRscC7qVQbRzhIwyqC7x9Tnm0gA4Qif+GoJV5aHQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ruHZtcdkGiHAwK7SMkpcnHNMr4Y0m/jFG47RZeRw7sE9RhgJQ/79Kxy/XF3JNSReC LFX7EkQxuODSiXy1orcYJi3b4n/sZKkO6THPCkmyTGnj4vFiJnVamRKAcz8PqIS/fk 5UYQlczDmsZ2mVmaRSXrPCy1IWfyxZMTEpiISPok= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Todd Kjos Subject: [PATCH 4.14 009/191] binder: fix UAF when releasing todo list Date: Tue, 27 Oct 2020 14:47:44 +0100 Message-Id: <20201027134910.162313126@linuxfoundation.org> X-Mailer: git-send-email 2.29.1 In-Reply-To: <20201027134909.701581493@linuxfoundation.org> References: <20201027134909.701581493@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@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 @@ -286,7 +286,7 @@ struct binder_device { struct binder_work { struct list_head entry; - enum { + enum binder_work_type { BINDER_WORK_TRANSACTION = 1, BINDER_WORK_TRANSACTION_COMPLETE, BINDER_WORK_RETURN_ERROR, @@ -850,27 +850,6 @@ 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); @@ -4162,13 +4141,17 @@ 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; @@ -4202,9 +4185,11 @@ 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; } }