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 3C6D0170A2E; Fri, 29 Mar 2024 12:34:35 +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=1711715675; cv=none; b=XqGoK0Cq3hYPUj/z5z/5rQEGj/0OXVDXx4K5HxspV5ar8JU20km4T1gvrFSHL64H53ZL2cDj6qGB55pUv/j6mOPho5t5C7DjjV3MXxNi5YG4ZHd3xUkf7XrUeXCrw/01m6SjgNcAp7aCb7tIYiZHavLgXMk3AQYMQWoNrejadaU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711715675; c=relaxed/simple; bh=vxSUUANd7m4g6XoA75yKSEMka/CZt4z3miE59J4d1vQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=WS7N9t1sssIRc8RysTCgoihMdxfZB2DesSWPJN0873w36xDUr6NO6X47stNS/jKk2e3TEE5VrPkHVTv30GQSt1AyzqZKpk0CF/+besdpdxQ3llpJZWb+XSUQVhcSyR6ecYf+JwMv1ZrB/VIUKQHiMuvpicabJ1oK3MXTOPjdGiE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DPS4uExo; 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="DPS4uExo" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A9FD5C433C7; Fri, 29 Mar 2024 12:34:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1711715675; bh=vxSUUANd7m4g6XoA75yKSEMka/CZt4z3miE59J4d1vQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DPS4uExoOXRIrbtTvkMk3GbqKsupck1DXhA4fp4nXo5rn3WlzM8Z5xVKMAyrDuSel nXknb4tFs1yW2rYjLopQrnlGvqrQtCOGaVMAN6XHtH0Zdm0IQHJJh1w/kBExbUmNBm bbNGJSjkVTIndtp79oCuKc5NgOQ2ERZ0AZg3Tzml0PO/NOjkiVevZH2CNvdxNemUFe c3yEnOzxS7ymCCJ9UoeIFeFGQ22n6ZnbEg+WfeX/6pbhJ5Gycber1Mnnqqs4I8DQZA rNi+H2onz3Mo+DHnFlyUWiInTYc+g4NAEBtWMQD4ZGf/Tz8DODjvjwuxaadAyUoo5w OqhT4fACCye7Q== 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 5.10 16/17] net/smc: reduce rtnl pressure in smc_pnet_create_pnetids_list() Date: Fri, 29 Mar 2024 08:33:55 -0400 Message-ID: <20240329123405.3086155-16-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240329123405.3086155-1-sashal@kernel.org> References: <20240329123405.3086155-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 5.10.214 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 30bae60d626c6..ed9cfa11b589f 100644 --- a/net/smc/smc_pnet.c +++ b/net/smc/smc_pnet.c @@ -797,6 +797,16 @@ 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