From patchwork Fri Dec 10 23:50:51 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 523383 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 DDA03C433F5 for ; Fri, 10 Dec 2021 23:51:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243870AbhLJXzW (ORCPT ); Fri, 10 Dec 2021 18:55:22 -0500 Received: from ams.source.kernel.org ([145.40.68.75]:40252 "EHLO ams.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233117AbhLJXzW (ORCPT ); Fri, 10 Dec 2021 18:55:22 -0500 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 B9ABFB82A34; Fri, 10 Dec 2021 23:51:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4DC88C341C8; Fri, 10 Dec 2021 23:51:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1639180304; bh=5vO/czztDFkpMlvLY/zKXkQqUQACt/mxzkFNJj6gVj0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=KeE/SY9HBXSShf0ol0GIs1l7VDsl/82UqgXmbIGpRpHh6i9P4rOElxH78SBTrY50R I5SAk/vVHLBydTn25wbqsNHAap8JbcdQR+PO1wBVV/Kt/yFCgcWGEpti4JaK4S3FSg B/t8dnFkKgnaqPQzYPVkgGZLE52FGe3Z47+je+te5Ic/A5VkdeMkoSlrj9IlJ6EOSA nAPJvPcsdofMJboPcnHlsaGu7LsEEWdR+6KzNqOxHDZW/Z94TTa2nl0H6O5C8dyVBU 3DcO13dA4tit+5uohjSHaQHrsGx48E+zaUfzz5XicswAyOB4f8nqydTDMekbToxuuC uU9vnnq3JNTEg== From: Eric Biggers To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Linus Torvalds Subject: [PATCH 5.4 2/5] binder: use wake_up_pollfree() Date: Fri, 10 Dec 2021 15:50:51 -0800 Message-Id: <20211210235054.40103-3-ebiggers@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20211210235054.40103-1-ebiggers@kernel.org> References: <20211210235054.40103-1-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 1cdc7426bd033..0512af0f04646 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -4788,23 +4788,20 @@ static int binder_thread_release(struct binder_proc *proc, __release(&t->lock); /* - * 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 inner 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, EPOLLHUP | POLLFREE); - } + if (thread->looper & BINDER_LOOPER_STATE_POLL) + wake_up_pollfree(&thread->wait); binder_inner_proc_unlock(thread->proc); /* - * 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();