From mboxrd@z Thu Jan 1 00:00:00 1970 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=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 D3C02C4709B for ; Thu, 3 Jun 2021 17:16:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BFD4F613DC for ; Thu, 3 Jun 2021 17:16:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233864AbhFCRSJ (ORCPT ); Thu, 3 Jun 2021 13:18:09 -0400 Received: from mail.kernel.org ([198.145.29.99]:43620 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233338AbhFCROK (ORCPT ); Thu, 3 Jun 2021 13:14:10 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 0599461413; Thu, 3 Jun 2021 17:10:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1622740259; bh=g4c31cHzQDbqDDuOrRuefwngoa8CJFoOdHRLyYsOp/o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=U43QfbaSAZnfdm2kl1JFRyQr+HChfL+vhUu98KzeNYj+asGs3kFT71cGx9Q46gVfK 3gjfUj8H6d9R5nhHvsXop0cw3xatfoMz2pxhyED5DIS7qIEu/4czsSfOk/UwLfAKjK Ivp80pigGsHFoi8dbbxT2eB0AGB2FwGtD2jeB/6BVTdQzeU8Mw0bN6bhpatfYgOw9V wpQxLpB23CdFiH2WdYS12YQdmGJqPgS5otNkQwTIjIuCjvRUoJ2hRkZX2q0m90Ow5g fY84zDbO9+TE9x8dQ2OV+lgpXi0++vYmBlNur5UJN8GSuo6ZgH8caDhTPji2OlHLEu w2uTbgBa4WeWw== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Johannes Berg , syzbot+69ff9dff50dcfe14ddd4@syzkaller.appspotmail.com, "David S . Miller" , Sasha Levin , netdev@vger.kernel.org Subject: [PATCH AUTOSEL 4.9 05/17] netlink: disable IRQs for netlink_lock_table() Date: Thu, 3 Jun 2021 13:10:40 -0400 Message-Id: <20210603171052.3169893-5-sashal@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210603171052.3169893-1-sashal@kernel.org> References: <20210603171052.3169893-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Johannes Berg [ Upstream commit 1d482e666b8e74c7555dbdfbfb77205eeed3ff2d ] Syzbot reports that in mac80211 we have a potential deadlock between our "local->stop_queue_reasons_lock" (spinlock) and netlink's nl_table_lock (rwlock). This is because there's at least one situation in which we might try to send a netlink message with this spinlock held while it is also possible to take the spinlock from a hardirq context, resulting in the following deadlock scenario reported by lockdep: CPU0 CPU1 ---- ---- lock(nl_table_lock); local_irq_disable(); lock(&local->queue_stop_reason_lock); lock(nl_table_lock); lock(&local->queue_stop_reason_lock); This seems valid, we can take the queue_stop_reason_lock in any kind of context ("CPU0"), and call ieee80211_report_ack_skb() with the spinlock held and IRQs disabled ("CPU1") in some code path (ieee80211_do_stop() via ieee80211_free_txskb()). Short of disallowing netlink use in scenarios like these (which would be rather complex in mac80211's case due to the deep callchain), it seems the only fix for this is to disable IRQs while nl_table_lock is held to avoid hitting this scenario, this disallows the "CPU0" portion of the reported deadlock. Note that the writer side (netlink_table_grab()) already disables IRQs for this lock. Unfortunately though, this seems like a huge hammer, and maybe the whole netlink table locking should be reworked. Reported-by: syzbot+69ff9dff50dcfe14ddd4@syzkaller.appspotmail.com Signed-off-by: Johannes Berg Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- net/netlink/af_netlink.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index 205865292ba3..541410f1c3b7 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -436,11 +436,13 @@ void netlink_table_ungrab(void) static inline void netlink_lock_table(void) { + unsigned long flags; + /* read_lock() synchronizes us to netlink_table_grab */ - read_lock(&nl_table_lock); + read_lock_irqsave(&nl_table_lock, flags); atomic_inc(&nl_table_users); - read_unlock(&nl_table_lock); + read_unlock_irqrestore(&nl_table_lock, flags); } static inline void -- 2.30.2