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 26CE4C47082 for ; Thu, 3 Jun 2021 17:17:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0F7E8613BA for ; Thu, 3 Jun 2021 17:17:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232642AbhFCRTH (ORCPT ); Thu, 3 Jun 2021 13:19:07 -0400 Received: from mail.kernel.org ([198.145.29.99]:43594 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233312AbhFCRQF (ORCPT ); Thu, 3 Jun 2021 13:16:05 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 081EA61447; Thu, 3 Jun 2021 17:11:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1622740281; bh=MAMQ78x0u265sFMbXfgRIrLXwkxSn0ebRdVeJrH3wVw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=b25JRgIHEpC/6bH4AS3LIbQCEbNuGYVIKeC3BQwcbkhfNAs4L878eoHVk8GNK0DaZ RPO0l92Pfno9EOxjOnArn/BGPgSvzTGG5ZBl9WvBuw+6QpzJhMrakQBdLD0PhOq2TV E91Eetq2Yf83vUcJMtKr5Kuzub7wcEOUvotB16EeFC4CX0fC1HGNhnMkek2abtVyDx oE9hF7PH2qnZzaGUNylOXajA+l6czH++LfXNR8Z8MZnX87B4bWGLdX3NdDyY7PMP4T RI+ghAGFHgtvA/pqXE+J5GtkBHsSwkeTlIRM1K60u/keTYT/jxlv+gj88svykFeChz f3cN3aotM5Ksg== 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 4.4 05/15] netlink: disable IRQs for netlink_lock_table() Date: Thu, 3 Jun 2021 13:11:04 -0400 Message-Id: <20210603171114.3170086-5-sashal@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210603171114.3170086-1-sashal@kernel.org> References: <20210603171114.3170086-1-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 cc37a219e11e..c20c41801845 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