From patchwork Sat Dec 11 00:28:31 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 523372 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 0B46EC433EF for ; Sat, 11 Dec 2021 00:28:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345473AbhLKAcY (ORCPT ); Fri, 10 Dec 2021 19:32:24 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56016 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345465AbhLKAcX (ORCPT ); Fri, 10 Dec 2021 19:32:23 -0500 Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 93190C061746; Fri, 10 Dec 2021 16:28:47 -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 sin.source.kernel.org (Postfix) with ESMTPS id DFA46CE2DDB; Sat, 11 Dec 2021 00:28:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F143BC341C8; Sat, 11 Dec 2021 00:28:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1639182524; bh=qpi9l/PqhmH2sxL4+/VUW06naq+hTMA57sGIqqM7cOk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=WJvA63xxl6Z0qb5/SDWRrVYBY3jb1S5IC7KYh3HecXZSZmbHa7spkpVl88DMquDtM h+ZWI7XZF7ekzVhDfLYUPNSEpw4SkSMK79Wb0h3XIayBV5kJu18l+2StO75ala1P0J DfDhWO1qccurq9IIommOPwPuntdquNl66OQAecX2vqz5pDXOFElHH4sgHspuV/GLsP +rtWhWjVYXUjAQsWROpwIqOWMJYxPAP5UlsVd5j5ujfEbWbsawEKTLUwoYbhdJVKiN 1Qyl4V1PcTAdx71tBvcD7MTnJQD/kxXaiNSPUfSUV1CnmogdqGauhe1uxknemSayKv V89/XCmQ+nzhg== From: Eric Biggers To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Linus Torvalds Subject: [PATCH 4.4,4.9 2/3] binder: use wake_up_pollfree() Date: Fri, 10 Dec 2021 16:28:31 -0800 Message-Id: <20211211002832.153742-3-ebiggers@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20211211002832.153742-1-ebiggers@kernel.org> References: <20211211002832.153742-1-ebiggers@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Eric Biggers commit a880b28a71e39013e357fd3adccd1d8a31bc69a8 upstream. wake_up_poll() uses nr_exclusive=1, so it's not guaranteed to wake up all exclusive waiters. Yet, POLLFREE *must* wake up all waiters. epoll and aio poll are fortunately not affected by this, but it's very fragile. Thus, the new function wake_up_pollfree() has been introduced. Convert binder to use wake_up_pollfree(). Reported-by: Linus Torvalds Fixes: f5cb779ba163 ("ANDROID: binder: remove waitqueue when thread exits.") Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20211209010455.42744-3-ebiggers@kernel.org Signed-off-by: Eric Biggers --- drivers/android/binder.c | 21 +++++++++------------ 1 file changed, 9 insertions(+), 12 deletions(-) diff --git a/drivers/android/binder.c b/drivers/android/binder.c index bf047f16fce9e..31a204ebfa6c5 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -2641,21 +2641,18 @@ static int binder_free_thread(struct binder_proc *proc, } /* - * If this thread used poll, make sure we remove the waitqueue - * from any epoll data structures holding it with POLLFREE. - * waitqueue_active() is safe to use here because we're holding - * the global lock. + * If this thread used poll, make sure we remove the waitqueue from any + * poll data structures holding it. */ - if ((thread->looper & BINDER_LOOPER_STATE_POLL) && - waitqueue_active(&thread->wait)) { - wake_up_poll(&thread->wait, POLLHUP | POLLFREE); - } + if (thread->looper & BINDER_LOOPER_STATE_POLL) + wake_up_pollfree(&thread->wait); /* - * This is needed to avoid races between wake_up_poll() above and - * and ep_remove_waitqueue() called for other reasons (eg the epoll file - * descriptor being closed); ep_remove_waitqueue() holds an RCU read - * lock, so we can be sure it's done after calling synchronize_rcu(). + * This is needed to avoid races between wake_up_pollfree() above and + * someone else removing the last entry from the queue for other reasons + * (e.g. ep_remove_wait_queue() being called due to an epoll file + * descriptor being closed). Such other users hold an RCU read lock, so + * we can be sure they're done after we call synchronize_rcu(). */ if (thread->looper & BINDER_LOOPER_STATE_POLL) synchronize_rcu();