From patchwork Tue Nov 15 20:28:57 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thomas Gleixner X-Patchwork-Id: 624928 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 56915C4332F for ; Tue, 15 Nov 2022 20:31:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237977AbiKOUbg (ORCPT ); Tue, 15 Nov 2022 15:31:36 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39522 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237900AbiKOUaU (ORCPT ); Tue, 15 Nov 2022 15:30:20 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BFDB430F78; Tue, 15 Nov 2022 12:29:00 -0800 (PST) Message-ID: <20221115202117.849485477@linutronix.de> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1668544138; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: references:references; bh=VMt+lAYwXqKzwEHThJOieOqFot6Ei0mDFg2C3AsrckQ=; b=mucQ8oXb0C4aCUY5JIMHL0lQvqrUa82sVbkH31UQxuzVpLZFZOmZrs0aoHSqp8pIGl/3ks XzbBlbaPcq7AdSa8X4h2kftgSOMVq0C5uEW1sgpJkvQoDwU0yqOrm1FD/muU/i1qildMby 3Hi4LCjz97NdVP1G1qQmV699Fe2I2dEXIR0EfIxNv/9KwsFNlwjyBEtPCFUJpSvHMhwFrM eA2HUfkCi7ahca5KpV4TI7TeG1Sbh22gIBXFxV3I+KZoNZpmsdlal4ZIax8x/yWtlwdybP FRU/wSK1ulaN4C96T3M46wWFUuj2HoJBfMu/F1M2zALqXL11TdMvSXtouh9STg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1668544138; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: references:references; bh=VMt+lAYwXqKzwEHThJOieOqFot6Ei0mDFg2C3AsrckQ=; b=OuvYR8kVkCDqlom60FXFh8tOQHo9j2OPSo2cnx3iin3PXTYDtXFF5m4yF0hgM7KN3NI2NA n/k4I9w9C1CNd/AQ== From: Thomas Gleixner To: LKML Cc: Linus Torvalds , Steven Rostedt , Anna-Maria Behnsen , Peter Zijlstra , Stephen Boyd , Guenter Roeck , Andrew Morton , Julia Lawall , Marcel Holtmann , Johan Hedberg , Luiz Augusto von Dentz , linux-bluetooth@vger.kernel.org, "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , netdev@vger.kernel.org, Arnd Bergmann , Viresh Kumar , Marc Zyngier Subject: [patch 15/15] Bluetooth: hci_qca: Fix the teardown problem for real References: <20221115195802.415956561@linutronix.de> MIME-Version: 1.0 Date: Tue, 15 Nov 2022 21:28:57 +0100 (CET) Precedence: bulk List-ID: X-Mailing-List: linux-bluetooth@vger.kernel.org While discussing solutions for the teardown problem which results from circular dependencies between timers and workqueues, where timers schedule work from their timer callback and workqueues arm the timers from work items, it was discovered that the recent fix to the QCA code is incorrect. That commit fixes the obvious problem of using del_timer() instead of del_timer_sync() and reorders the teardown calls to destroy_workqueue(wq); del_timer_sync(t); This makes it less likely to explode, but it's still broken: destroy_workqueue(wq); /* After this point @wq cannot be touched anymore */ ---> timer expires queue_work(wq) <---- Results in a NULl pointer dereference deep in the work queue core code. del_timer_sync(t); Use the new timer_shutdown_sync() function to ensure that the timers are disarmed, no timer callbacks are running and the timers cannot be armed again. This restores the original teardown sequence: timer_shutdown_sync(t); destroy_workqueue(wq); which is now correct because the timer core silently ignores potential rearming attempts which can happen when destroy_workqueue() drains pending work before mopping up the workqueue. Fixes: 72ef98445aca ("Bluetooth: hci_qca: Use del_timer_sync() before freeing") Signed-off-by: Thomas Gleixner Cc: Marcel Holtmann Cc: Johan Hedberg Cc: Luiz Augusto von Dentz Cc: linux-bluetooth@vger.kernel.org Cc: "David S. Miller" Cc: Eric Dumazet Cc: Jakub Kicinski Cc: Paolo Abeni Cc: netdev@vger.kernel.org Link: https://lore.kernel.org/all/87iljhsftt.ffs@tglx Acked-by: Luiz Augusto von Dentz --- drivers/bluetooth/hci_qca.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) --- a/drivers/bluetooth/hci_qca.c +++ b/drivers/bluetooth/hci_qca.c @@ -696,9 +696,15 @@ static int qca_close(struct hci_uart *hu skb_queue_purge(&qca->tx_wait_q); skb_queue_purge(&qca->txq); skb_queue_purge(&qca->rx_memdump_q); + /* + * Shut the timers down so they can't be rearmed when + * destroy_workqueue() drains pending work which in turn might try + * to arm a timer. After shutdown rearm attempts are silently + * ignored by the timer core code. + */ + timer_shutdown_sync(&qca->tx_idle_timer); + timer_shutdown_sync(&qca->wake_retrans_timer); destroy_workqueue(qca->workqueue); - del_timer_sync(&qca->tx_idle_timer); - del_timer_sync(&qca->wake_retrans_timer); qca->hu = NULL; kfree_skb(qca->rx_skb);