From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5077785950; Fri, 29 Mar 2024 12:31:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711715503; cv=none; b=TdjkRFfmAAhj7ZxmNpyTaonnh+zwzRr0G9GDXcKOeaOROs/Yq7FWR6+8ryEAqVr4zbpozKQVM9Z9O5kw4g1xAPOoSBIK0p0KfvKGKTH6h2OHkpYxi9Z/4pvynvXwUe7iZaCBCmG3lZfUwIHNM9HJfBury8h9jnXMh1glEkd2HFU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711715503; c=relaxed/simple; bh=j8U475whEhGW3JJ7l7qtS1Liv/9lLh+Dt6gwp1HXrjM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ZU56n576Il8e6FQUsBS7LjrmtrS0FytOUZ+xG5SkpUij1a+TYfHX8TFB1eIs7SfllLeLYKSX/JtnK/853Cla/Uds3gUvG+jqodpaIPqV/8GEMPFgbTf49VPVCb7IcZzgSRPPavYQM6VUW1jHHh46diiJPwEjJmgwdfz/UdNlSHY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=OnlG+yde; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="OnlG+yde" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 707D1C43399; Fri, 29 Mar 2024 12:31:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1711715502; bh=j8U475whEhGW3JJ7l7qtS1Liv/9lLh+Dt6gwp1HXrjM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=OnlG+ydedKYFTtbbonaXvxdPyjO8XxFc+X9oB2ej6S7geocIUN3RoGCYCWgyM8y5N 3X8PMuwg4tGbiEkQyEd7fFSZATtNq2E0UhQyrvu8P59ZyIhqR3CyCUtuTY54/uhvAm 1Q3wxUNmzcs5Kzy0AYq/XeIBwqXWBcLnpZOS06wZY1iRrUZu9E2N83MhZsSEZv5pKK WnzV+U7lXGM0E93+PQGzTYKXBIbZOn0BQ602SEkwAyr/jJT3PiZN2bY1BMkn0SpQxS UUhmKpP8WiyJEskc6elKeS0PV5ejD33GuSSidh5OUaThCEB/MetW7KfTV0KdmzAJms 5gb5PFYDeVdmQ== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Eric Dumazet , Wenjia Zhang , Jan Karcher , "D. Wythe" , Tony Lu , Wen Gu , Paolo Abeni , Sasha Levin , davem@davemloft.net, kuba@kernel.org, linux-s390@vger.kernel.org, netdev@vger.kernel.org Subject: [PATCH AUTOSEL 6.6 49/52] net/smc: reduce rtnl pressure in smc_pnet_create_pnetids_list() Date: Fri, 29 Mar 2024 08:29:19 -0400 Message-ID: <20240329122956.3083859-49-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240329122956.3083859-1-sashal@kernel.org> References: <20240329122956.3083859-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.6.23 Content-Transfer-Encoding: 8bit From: Eric Dumazet [ Upstream commit 00af2aa93b76b1bade471ad0d0525d4d29ca5cc0 ] Many syzbot reports show extreme rtnl pressure, and many of them hint that smc acquires rtnl in netns creation for no good reason [1] This patch returns early from smc_pnet_net_init() if there is no netdevice yet. I am not even sure why smc_pnet_create_pnetids_list() even exists, because smc_pnet_netdev_event() is also calling smc_pnet_add_base_pnetid() when handling NETDEV_UP event. [1] extract of typical syzbot reports 2 locks held by syz-executor.3/12252: #0: ffffffff8f369610 (pernet_ops_rwsem){++++}-{3:3}, at: copy_net_ns+0x4c7/0x7b0 net/core/net_namespace.c:491 #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_create_pnetids_list net/smc/smc_pnet.c:809 [inline] #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_net_init+0x10a/0x1e0 net/smc/smc_pnet.c:878 2 locks held by syz-executor.4/12253: #0: ffffffff8f369610 (pernet_ops_rwsem){++++}-{3:3}, at: copy_net_ns+0x4c7/0x7b0 net/core/net_namespace.c:491 #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_create_pnetids_list net/smc/smc_pnet.c:809 [inline] #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_net_init+0x10a/0x1e0 net/smc/smc_pnet.c:878 2 locks held by syz-executor.1/12257: #0: ffffffff8f369610 (pernet_ops_rwsem){++++}-{3:3}, at: copy_net_ns+0x4c7/0x7b0 net/core/net_namespace.c:491 #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_create_pnetids_list net/smc/smc_pnet.c:809 [inline] #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_net_init+0x10a/0x1e0 net/smc/smc_pnet.c:878 2 locks held by syz-executor.2/12261: #0: ffffffff8f369610 (pernet_ops_rwsem){++++}-{3:3}, at: copy_net_ns+0x4c7/0x7b0 net/core/net_namespace.c:491 #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_create_pnetids_list net/smc/smc_pnet.c:809 [inline] #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_net_init+0x10a/0x1e0 net/smc/smc_pnet.c:878 2 locks held by syz-executor.0/12265: #0: ffffffff8f369610 (pernet_ops_rwsem){++++}-{3:3}, at: copy_net_ns+0x4c7/0x7b0 net/core/net_namespace.c:491 #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_create_pnetids_list net/smc/smc_pnet.c:809 [inline] #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_net_init+0x10a/0x1e0 net/smc/smc_pnet.c:878 2 locks held by syz-executor.3/12268: #0: ffffffff8f369610 (pernet_ops_rwsem){++++}-{3:3}, at: copy_net_ns+0x4c7/0x7b0 net/core/net_namespace.c:491 #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_create_pnetids_list net/smc/smc_pnet.c:809 [inline] #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_net_init+0x10a/0x1e0 net/smc/smc_pnet.c:878 2 locks held by syz-executor.4/12271: #0: ffffffff8f369610 (pernet_ops_rwsem){++++}-{3:3}, at: copy_net_ns+0x4c7/0x7b0 net/core/net_namespace.c:491 #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_create_pnetids_list net/smc/smc_pnet.c:809 [inline] #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_net_init+0x10a/0x1e0 net/smc/smc_pnet.c:878 2 locks held by syz-executor.1/12274: #0: ffffffff8f369610 (pernet_ops_rwsem){++++}-{3:3}, at: copy_net_ns+0x4c7/0x7b0 net/core/net_namespace.c:491 #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_create_pnetids_list net/smc/smc_pnet.c:809 [inline] #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_net_init+0x10a/0x1e0 net/smc/smc_pnet.c:878 2 locks held by syz-executor.2/12280: #0: ffffffff8f369610 (pernet_ops_rwsem){++++}-{3:3}, at: copy_net_ns+0x4c7/0x7b0 net/core/net_namespace.c:491 #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_create_pnetids_list net/smc/smc_pnet.c:809 [inline] #1: ffffffff8f375b88 (rtnl_mutex){+.+.}-{3:3}, at: smc_pnet_net_init+0x10a/0x1e0 net/smc/smc_pnet.c:878 Signed-off-by: Eric Dumazet Cc: Wenjia Zhang Cc: Jan Karcher Cc: "D. Wythe" Cc: Tony Lu Cc: Wen Gu Reviewed-by: Wenjia Zhang Link: https://lore.kernel.org/r/20240302100744.3868021-1-edumazet@google.com Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin --- net/smc/smc_pnet.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/net/smc/smc_pnet.c b/net/smc/smc_pnet.c index 11775401df689..306b536fa89e9 100644 --- a/net/smc/smc_pnet.c +++ b/net/smc/smc_pnet.c @@ -806,6 +806,16 @@ static void smc_pnet_create_pnetids_list(struct net *net) u8 ndev_pnetid[SMC_MAX_PNETID_LEN]; struct net_device *dev; + /* Newly created netns do not have devices. + * Do not even acquire rtnl. + */ + if (list_empty(&net->dev_base_head)) + return; + + /* Note: This might not be needed, because smc_pnet_netdev_event() + * is also calling smc_pnet_add_base_pnetid() when handling + * NETDEV_UP event. + */ rtnl_lock(); for_each_netdev(net, dev) smc_pnet_add_base_pnetid(net, dev, ndev_pnetid); -- 2.43.0