From patchwork Sat Dec 11 00:28:32 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 523373 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 8A7E4C433FE for ; Sat, 11 Dec 2021 00:28:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241482AbhLKAcW (ORCPT ); Fri, 10 Dec 2021 19:32:22 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56012 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244279AbhLKAcW (ORCPT ); Fri, 10 Dec 2021 19:32:22 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B49E5C061714; Fri, 10 Dec 2021 16:28:46 -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 ams.source.kernel.org (Postfix) with ESMTPS id 80C0AB82A4A; Sat, 11 Dec 2021 00:28:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3A114C341CA; Sat, 11 Dec 2021 00:28:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1639182524; bh=XuaZ1fZ6TwT9fwMbUAdcVm8nv57KY1gx1t0F0FZ5++o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=TDEJfKUPBqkEOTsZ9D35lUwCEG8DDVjBINAjB/pDg89ibdvTEkM4cZGDxUKY1lo86 8ShIaWg63ZuTczE3pekMNneJ/hLcghUF2yJOYgx5/nas3RNfsjVhC14+Kkj9HCUIzi 340DIgASHmULinIHKjgw9RBpa3ETlG6TExDtQR0xZ3lbHEzVVsPMydTpEfVndk1Vpn 4BM78qwYih9FL341priu19QTNYkRcoouyXPV25cTOpeIJCwKbH8+DblGukji2Idjsv WpGpq2XbVN3b1ETRM1QuOUgr8Ydbb48TnurP5QDO0cin8yBaA5YkwabKtdCq4o8p2z d4ucKqUpgn6nA== From: Eric Biggers To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Linus Torvalds Subject: [PATCH 4.4,4.9 3/3] signalfd: use wake_up_pollfree() Date: Fri, 10 Dec 2021 16:28:32 -0800 Message-Id: <20211211002832.153742-4-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 9537bae0da1f8d1e2361ab6d0479e8af7824e160 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 signalfd to use wake_up_pollfree(). Reported-by: Linus Torvalds Fixes: d80e731ecab4 ("epoll: introduce POLLFREE to flush ->signalfd_wqh before kfree()") Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20211209010455.42744-4-ebiggers@kernel.org Signed-off-by: Eric Biggers --- fs/signalfd.c | 12 +----------- 1 file changed, 1 insertion(+), 11 deletions(-) diff --git a/fs/signalfd.c b/fs/signalfd.c index 270221fcef42c..9c5fa0ab5e0fe 100644 --- a/fs/signalfd.c +++ b/fs/signalfd.c @@ -34,17 +34,7 @@ void signalfd_cleanup(struct sighand_struct *sighand) { - wait_queue_head_t *wqh = &sighand->signalfd_wqh; - /* - * The lockless check can race with remove_wait_queue() in progress, - * but in this case its caller should run under rcu_read_lock() and - * sighand_cachep is SLAB_DESTROY_BY_RCU, we can safely return. - */ - if (likely(!waitqueue_active(wqh))) - return; - - /* wait_queue_t->func(POLLFREE) should do remove_wait_queue() */ - wake_up_poll(wqh, POLLHUP | POLLFREE); + wake_up_pollfree(&sighand->signalfd_wqh); } struct signalfd_ctx {