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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C0074C43334 for ; Fri, 22 Jul 2022 19:34:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236331AbiGVTej (ORCPT ); Fri, 22 Jul 2022 15:34:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35620 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232157AbiGVTei (ORCPT ); Fri, 22 Jul 2022 15:34:38 -0400 Received: from mail-ej1-x635.google.com (mail-ej1-x635.google.com [IPv6:2a00:1450:4864:20::635]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 02DE851A1F for ; Fri, 22 Jul 2022 12:34:37 -0700 (PDT) Received: by mail-ej1-x635.google.com with SMTP id mf4so10252817ejc.3 for ; Fri, 22 Jul 2022 12:34:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=lR1hZw0XukXpRfFvnSBQAvUqz/OTx4MLjptGdrtodks=; b=RmWZsbClWP7Fh/dEvfMZZIOjGBmiGK+YAv8r0SldDmAZSzO7RZQ1R6ZZsjpT2IkvmC db4+XkEFrBvzDTuYFlN2tfNuG5PLwNPu1zNgL0IIFI0bkxC6c7RllPHF4ljJNWI0hW9Y 7xhtPuKQ+leyCbWiN2i+9wBr1DHsef1ZRkHkMpxka9vWWOXbT/hPsVa+KwPmDFdLN++8 iJVTc8coXzJ1t8nFcuJMRq8xebx8mK/UnfgjRIlbAYqLjUGIeVKbWvivjB+r31ir7TcO LcTu6s24DZ0fDqwPkDVFuePBY4lY6blXIWa69Y/FgXxbq8xrK94lHEoudYQIJvV92YUt haBQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=lR1hZw0XukXpRfFvnSBQAvUqz/OTx4MLjptGdrtodks=; b=sg/UjarKvar3GwERrKg7+pgSAL7zHpHX6UR1CZypImPiD0vEYPfBTRKtSUmGt1OFth PayMKjaM0jlfaf749km7SXkuOc2tyQPVCRgPisHm+NAsarjonA46cnqG9I4e1QsBg7MR 8GWrI0aO+Ap51JbuVJhlL39sHpdsFqhKtJLtRVTe8N4rdaWTIMZL8oOa9h/jsth+BbrZ qVc4jw0mMem/Mm2P7NimFgkO4usNYjGNcSpaPRa9GwWtl/uU85MC9/928LTPJHpOjKSl A8e7VGxjvL3qNWlFOzh+5CRK9/S6rQUAWCCa+Bu630lTAPI71Dd7GftbfQ5zLN5MMHjP LT0A== X-Gm-Message-State: AJIora+kzjtr+WpiAg45tDvekjWcEj/Oad1PmoLEemg38+Ceq8wJtVCM ZaBHY4cXQ7JrY0i3iNwJJhs= X-Google-Smtp-Source: AGRyM1sFlh+eb5/k0Y3cAejYshv0yjFKwRVwNo5LjTUwWOX6tAmmppRXWfAFkMnIK5sbGABIC/OIpw== X-Received: by 2002:a17:907:2cf3:b0:72b:8ac1:a21f with SMTP id hz19-20020a1709072cf300b0072b8ac1a21fmr1068785ejc.291.1658518475312; Fri, 22 Jul 2022 12:34:35 -0700 (PDT) Received: from skbuf ([188.25.231.115]) by smtp.gmail.com with ESMTPSA id l10-20020a170906938a00b006f3ef214daesm2349416ejx.20.2022.07.22.12.34.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 22 Jul 2022 12:34:34 -0700 (PDT) Date: Fri, 22 Jul 2022 22:34:32 +0300 From: Vladimir Oltean To: Eric Dumazet Cc: "David S . Miller" , Jakub Kicinski , Paolo Abeni , netdev@vger.kernel.org, eric.dumazet@gmail.com Subject: Re: [PATCH v2 net-next 08/19] ipmr: do not acquire mrt_lock while calling ip_mr_forward() Message-ID: <20220722193432.zdcnnxyigq2yozok@skbuf> References: <20220623043449.1217288-1-edumazet@google.com> <20220623043449.1217288-1-edumazet@google.com> <20220623043449.1217288-9-edumazet@google.com> <20220623043449.1217288-9-edumazet@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220623043449.1217288-9-edumazet@google.com> <20220623043449.1217288-9-edumazet@google.com> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Hi Eric, On Thu, Jun 23, 2022 at 04:34:38AM +0000, Eric Dumazet wrote: > ip_mr_forward() uses standard RCU protection already. > > Signed-off-by: Eric Dumazet > --- > net/ipv4/ipmr.c | 9 ++------- > 1 file changed, 2 insertions(+), 7 deletions(-) > > diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c > index 6ea54bc3d9b6555aaa9974d81ba4acd47481724f..b0f2e6d79d62273c8c2682f28cb45fe5ec3df6f3 100644 > --- a/net/ipv4/ipmr.c > +++ b/net/ipv4/ipmr.c > @@ -1817,7 +1817,7 @@ static bool ipmr_forward_offloaded(struct sk_buff *skb, struct mr_table *mrt, > } > #endif > > -/* Processing handlers for ipmr_forward */ > +/* Processing handlers for ipmr_forward, under rcu_read_lock() */ > > static void ipmr_queue_xmit(struct net *net, struct mr_table *mrt, > int in_vifi, struct sk_buff *skb, int vifi) > @@ -1839,9 +1839,7 @@ static void ipmr_queue_xmit(struct net *net, struct mr_table *mrt, > WRITE_ONCE(vif->bytes_out, vif->bytes_out + skb->len); > vif_dev->stats.tx_bytes += skb->len; > vif_dev->stats.tx_packets++; > - rcu_read_lock(); > ipmr_cache_report(mrt, skb, vifi, IGMPMSG_WHOLEPKT); > - rcu_read_unlock(); > goto out_free; > } > > @@ -1936,6 +1934,7 @@ static int ipmr_find_vif(const struct mr_table *mrt, struct net_device *dev) > } > > /* "local" means that we should preserve one skb (for local delivery) */ > +/* Called uner rcu_read_lock() */ > static void ip_mr_forward(struct net *net, struct mr_table *mrt, > struct net_device *dev, struct sk_buff *skb, > struct mfc_cache *c, int local) > @@ -1992,12 +1991,10 @@ static void ip_mr_forward(struct net *net, struct mr_table *mrt, > c->_c.mfc_un.res.last_assert + > MFC_ASSERT_THRESH)) { > c->_c.mfc_un.res.last_assert = jiffies; > - rcu_read_lock(); > ipmr_cache_report(mrt, skb, true_vifi, IGMPMSG_WRONGVIF); > if (mrt->mroute_do_wrvifwhole) > ipmr_cache_report(mrt, skb, true_vifi, > IGMPMSG_WRVIFWHOLE); > - rcu_read_unlock(); > } > goto dont_forward; > } > @@ -2169,9 +2166,7 @@ int ip_mr_input(struct sk_buff *skb) > return -ENODEV; > } > > - read_lock(&mrt_lock); > ip_mr_forward(net, mrt, dev, skb, cache, local); > - read_unlock(&mrt_lock); > > if (local) > return ip_local_deliver(skb); > -- > 2.37.0.rc0.104.g0611611a94-goog > Sorry for reporting this late, but there seems to be 1 call path from which RCU is not watching in ip_mr_forward(). It's via ipmr_mfc_add() -> ipmr_cache_resolve() -> ip_mr_forward(). The warning looks like this: [ 632.062382] ============================= [ 632.068568] WARNING: suspicious RCU usage [ 632.073702] 5.19.0-rc7-07010-ga9b9500ffaac-dirty #3374 Not tainted [ 632.081098] ----------------------------- [ 632.086216] net/ipv4/ipmr.c:1080 suspicious rcu_dereference_check() usage! [ 632.094152] [ 632.094152] other info that might help us debug this: [ 632.103349] [ 632.103349] rcu_scheduler_active = 2, debug_locks = 1 [ 632.111011] 1 lock held by smcrouted/359: [ 632.116079] #0: ffffd27b44d23770 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock+0x1c/0x30 [ 632.124703] [ 632.124703] stack backtrace: [ 632.129681] CPU: 0 PID: 359 Comm: smcrouted Not tainted 5.19.0-rc7-07010-ga9b9500ffaac-dirty #3374 [ 632.143426] Call trace: [ 632.160542] lockdep_rcu_suspicious+0xf8/0x10c [ 632.165014] ipmr_cache_report+0x2f0/0x530 [ 632.169137] ip_mr_forward+0x364/0x38c [ 632.172909] ipmr_mfc_add+0x894/0xc90 [ 632.176592] ip_mroute_setsockopt+0x6ac/0x950 [ 632.180973] ip_setsockopt+0x16a0/0x16ac [ 632.184921] raw_setsockopt+0x110/0x184 [ 632.188780] sock_common_setsockopt+0x1c/0x2c [ 632.193163] __sys_setsockopt+0x94/0x170 [ 632.197111] __arm64_sys_setsockopt+0x2c/0x40 [ 632.201492] invoke_syscall+0x48/0x114 I don't exactly understand the data structures that are used inside ip_mr_forward(), so I'm unable to say what needs RCU protection and what is fine with the rtnl_mutex that we are holding, just annotated poorly. Could you please take a look?