From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-vk1-f201.google.com (mail-vk1-f201.google.com [209.85.221.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F2C4031E82A for ; Mon, 18 May 2026 10:01:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779098503; cv=none; b=Ul7RvBHxUHZ99z9357t5aFkSMdyQfxtMvwO412pWO0aNoEuvWxzQRRIfC6OI186IbMxu7b1i8xGTZVGrCmzGwzrDxNy6KIJCFoM1aOItn3H4n1cmTGSQqnsTZaXPh2b9roWXzPlesnjg1lRbOEKm8Z5G+UdA40766DCB6+WhtU0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779098503; c=relaxed/simple; bh=+4IEKH4TXYQOE9RkQ8CPBajL8OlptaIodiMwMJEfS04=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=sHhotynqWWFL7SqzBGMZRU0vvO1vRjK0NOeYJncHnLX5NoT9MHRKOcH/SNnZxbvZT2asp2JEdWT4YRi56ujNuPuqmJmvQQp5xXmbpVoX8mocUizZashhe/5VfP+idlCV7yy6zOMPeAd8Mkuun8qWynnVH5VhYndFhx3tfJWfm9I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--edumazet.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=lj4U2Gk0; arc=none smtp.client-ip=209.85.221.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--edumazet.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="lj4U2Gk0" Received: by mail-vk1-f201.google.com with SMTP id 71dfb90a1353d-5752402f55aso1073194e0c.2 for ; Mon, 18 May 2026 03:01:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1779098499; x=1779703299; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=xZKjj/nIpnkj9FtvcO0L8vwOF8zvejZPfy7qESYcgRw=; b=lj4U2Gk0StW6ebDUHSeUiFDu54OiaVfl/joPpo5ULKfu6hwbQ987KA/6EnaXp0h3rF XjlM6rz5bJZWXktGfH/Cghg9uuoiVOfpU9DYGvb9PAmRCkHOd+qwtbiNmgocU3BqqNDv Dxniu3DnKbEM9nA+6IQlGTS4966y+/STF5BMYL+GadgDEIeimSotn9QNdiNlWAVLwPme dW6nFBzyVUcN/IO8b1WVjfvQ1uFuna6WiHa5ZwQgrqCQh+LcL1wvgXTcY5wHkntcylRf FrWxvf1rYOeat6gRc+pqxaen+5juOkLHgOvvfNfoRYLjEFcfEtWsc8XWisy5bKaOLbWb n+0g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1779098499; x=1779703299; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=xZKjj/nIpnkj9FtvcO0L8vwOF8zvejZPfy7qESYcgRw=; b=XCs3EGW5XdRoU0Z7NgFJwsJwanvU0MrmNyr45mCGE85VCEvNSHxpXBOX1UbUwfTsOQ TnjBirENsnz+AvEPs26x7EWGk431GkfsVbs3w+zDBDDJvH7yoaaUH5q79dG/dlhZmIuI tRvVeRuc4WuLOIboJmSO5jPXupyVFCc8i4cbA+JB0LQesKFXUfziCzPy3/iqBpC5L6as DZRoOitHdYyGfqBM537OyiD0WDlpd1UAVaTYC/SWDvb282qOqZshRRxW3ETsVkJlRx9u 9dA3ihIRfitIM3OXxIt0q2dUqU9No3J22rxrU+9t0KyghdZY7tVgJ74GIq4FgCDMgTLa khOQ== X-Forwarded-Encrypted: i=1; AFNElJ8bS6mJHH8C32N4Tdu0CymjKCEQm0SawWvlDqZ275T/BS6cJX0fZYR2eMAwEW2SANN7+GaLkEU=@vger.kernel.org X-Gm-Message-State: AOJu0YzAMmQcbBHlxiYkr5cQUG4c8JSs96ScXlWNR5h7H8OP4tH61BkG xyj9HOA1hv7t0HDpzgq9UXuyTsKf8a3ZPD43JMftLfqSEIMAquALpQjH6m9h/63zTNLvYYHed5a wrHA03AizZxK9Bg== X-Received: from qknqk5.prod.google.com ([2002:a05:620a:8885:b0:910:c453:28]) (user=edumazet job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6122:8f8c:b0:56d:b639:5c0d with SMTP id 71dfb90a1353d-5760c1f3533mr6643161e0c.13.1779098499194; Mon, 18 May 2026 03:01:39 -0700 (PDT) Date: Mon, 18 May 2026 10:01:34 +0000 In-Reply-To: <20260518100134.809042-1-edumazet@google.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260518100134.809042-1-edumazet@google.com> X-Mailer: git-send-email 2.54.0.563.g4f69b47b94-goog Message-ID: <20260518100134.809042-3-edumazet@google.com> Subject: [PATCH net-next 2/2] rtnetlink: do not acquire RTNL for RTM_GETLINK with RTEXT_FILTER_NAME_ONLY From: Eric Dumazet To: "David S . Miller" , Jakub Kicinski , Paolo Abeni Cc: Kuniyuki Iwashima , Simon Horman , netdev@vger.kernel.org, eric.dumazet@gmail.com, Eric Dumazet Content-Type: text/plain; charset="UTF-8" When RTEXT_FILTER_NAME_ONLY is requested, rtnl_fill_ifinfo() is dumping device attributes which do not need RTNL protection. Many shell scripts invoke iproute2 commands specifying a device by its name. After this patch, they will no longer add RTNL pressure. Signed-off-by: Eric Dumazet --- net/core/rtnetlink.c | 70 ++++++++++++++++++++++++++++++++------------ 1 file changed, 51 insertions(+), 19 deletions(-) diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c index ae0254f19178735b2805a8189e81a960a49b2858..8fe6260a0feaeea7ba35ddca3c1942f1420aecae 100644 --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -3468,6 +3468,21 @@ static struct net_device *rtnl_dev_get(struct net *net, return __dev_get_by_name(net, ifname); } +static struct net_device *rtnl_dev_get_rcu(struct net *net, + struct nlattr *tb[]) +{ + char ifname[ALTIFNAMSIZ]; + + if (tb[IFLA_IFNAME]) + nla_strscpy(ifname, tb[IFLA_IFNAME], IFNAMSIZ); + else if (tb[IFLA_ALT_IFNAME]) + nla_strscpy(ifname, tb[IFLA_ALT_IFNAME], ALTIFNAMSIZ); + else + return NULL; + + return dev_get_by_name_rcu(net, ifname); +} + static int rtnl_setlink(struct sk_buff *skb, struct nlmsghdr *nlh, struct netlink_ext_ack *extack) { @@ -4187,14 +4202,15 @@ static int rtnl_getlink(struct sk_buff *skb, struct nlmsghdr *nlh, struct netlink_ext_ack *extack) { struct net *net = sock_net(skb->sk); + struct nlattr *tb[IFLA_MAX + 1]; + netdevice_tracker dev_tracker; + struct net_device *dev = NULL; struct net *tgt_net = net; + u32 ext_filter_mask = 0; struct ifinfomsg *ifm; - struct nlattr *tb[IFLA_MAX+1]; - struct net_device *dev = NULL; struct sk_buff *nskb; int netnsid = -1; int err; - u32 ext_filter_mask = 0; err = rtnl_valid_getlink_req(skb, nlh, tb, extack); if (err < 0) @@ -4214,14 +4230,19 @@ static int rtnl_getlink(struct sk_buff *skb, struct nlmsghdr *nlh, if (tb[IFLA_EXT_MASK]) ext_filter_mask = nla_get_u32(tb[IFLA_EXT_MASK]); - err = -EINVAL; ifm = nlmsg_data(nlh); - if (ifm->ifi_index > 0) - dev = __dev_get_by_index(tgt_net, ifm->ifi_index); - else if (tb[IFLA_IFNAME] || tb[IFLA_ALT_IFNAME]) - dev = rtnl_dev_get(tgt_net, tb); - else + rcu_read_lock(); + if (ifm->ifi_index > 0) { + dev = dev_get_by_index_rcu(tgt_net, ifm->ifi_index); + } else if (tb[IFLA_IFNAME] || tb[IFLA_ALT_IFNAME]) { + dev = rtnl_dev_get_rcu(tgt_net, tb); + } else { + rcu_read_unlock(); + err = -EINVAL; goto out; + } + netdev_hold(dev, &dev_tracker, GFP_ATOMIC); + rcu_read_unlock(); err = -ENODEV; if (dev == NULL) @@ -4232,25 +4253,35 @@ static int rtnl_getlink(struct sk_buff *skb, struct nlmsghdr *nlh, if (nskb == NULL) goto out; - /* Synchronize the carrier state so we don't report a state - * that we're not actually going to honour immediately; if - * the driver just did a carrier off->on transition, we can - * only TX if link watch work has run, but without this we'd - * already report carrier on, even if it doesn't work yet. - */ - linkwatch_sync_dev(dev); + if (!(ext_filter_mask & RTEXT_FILTER_NAME_ONLY)) { + rtnl_lock(); + /* Synchronize the carrier state so we don't report a state + * that we're not actually going to honour immediately; if + * the driver just did a carrier off->on transition, we can + * only TX if link watch work has run, but without this we'd + * already report carrier on, even if it doesn't work yet. + */ + linkwatch_sync_dev(dev); + } err = rtnl_fill_ifinfo(nskb, dev, net, RTM_NEWLINK, NETLINK_CB(skb).portid, nlh->nlmsg_seq, 0, 0, ext_filter_mask, 0, NULL, 0, netnsid, GFP_KERNEL); + + if (!(ext_filter_mask & RTEXT_FILTER_NAME_ONLY)) + rtnl_unlock(); + if (err < 0) { /* -EMSGSIZE implies BUG in if_nlmsg_size */ - WARN_ON(err == -EMSGSIZE); + WARN_ON_ONCE(err == -EMSGSIZE && + !(ext_filter_mask & RTEXT_FILTER_NAME_ONLY)); kfree_skb(nskb); - } else + } else { err = rtnl_unicast(nskb, net, NETLINK_CB(skb).portid); + } out: + netdev_put(dev, &dev_tracker); if (netnsid >= 0) put_net(tgt_net); @@ -7116,7 +7147,8 @@ static const struct rtnl_msg_handler rtnetlink_rtnl_msg_handlers[] __initconst = {.msgtype = RTM_DELLINK, .doit = rtnl_dellink, .flags = RTNL_FLAG_DOIT_PERNET_WIP}, {.msgtype = RTM_GETLINK, .doit = rtnl_getlink, - .dumpit = rtnl_dump_ifinfo, .flags = RTNL_FLAG_DUMP_SPLIT_NLM_DONE}, + .dumpit = rtnl_dump_ifinfo, + .flags = RTNL_FLAG_DUMP_SPLIT_NLM_DONE | RTNL_FLAG_DOIT_UNLOCKED}, {.msgtype = RTM_SETLINK, .doit = rtnl_setlink, .flags = RTNL_FLAG_DOIT_PERNET_WIP}, {.msgtype = RTM_GETADDR, .dumpit = rtnl_dump_all}, -- 2.54.0.563.g4f69b47b94-goog