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 56B7DC47082 for ; Thu, 3 Jun 2021 17:08:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 453C2613F6 for ; Thu, 3 Jun 2021 17:08:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231784AbhFCRKN (ORCPT ); Thu, 3 Jun 2021 13:10:13 -0400 Received: from mail.kernel.org ([198.145.29.99]:40812 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229924AbhFCRJo (ORCPT ); Thu, 3 Jun 2021 13:09:44 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id EB461613F9; Thu, 3 Jun 2021 17:07:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1622740079; bh=6ph0Xmv0g6w1/Ra30QvkelGmVFaqyN7LO4bblU86F6o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UBHfSO79VLObSTu8hCGZst/m3moXtLfZ/H8yw2JMf9i6PY36ETzkBA0uhkF6o5nsk LRf3CN4NV55sW//gORRU4j/7CemJeEqLwJjG60nlg+uUQwaf3og3e0K5uH/qnINTp7 lBo4JicnQC4lYbrm4SEJuymib8n/4dcWd+R1gYCqwbA/tufV8Tbsp+2A03aJCqCwLV 3U25jL9ILx2++TS3mQ8jhRDtQcFYcoWeocSB08VQqBCkfdvmNx5o2R3v+i2zsPx7ZO OrVwPSw/AIHTZO/JFMOvztFK3Wnax8P6bTY5GFRbglFjPtk08xJk9C7HMB6N7zgAT/ f8aEtLcXWChYw== 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 5.12 20/43] netlink: disable IRQs for netlink_lock_table() Date: Thu, 3 Jun 2021 13:07:10 -0400 Message-Id: <20210603170734.3168284-20-sashal@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210603170734.3168284-1-sashal@kernel.org> References: <20210603170734.3168284-1-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 3a62f97acf39..6133e412b948 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -461,11 +461,13 @@ 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