From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qv1-f74.google.com (mail-qv1-f74.google.com [209.85.219.74]) (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 39FF9331A6E for ; Tue, 19 May 2026 11:44:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.74 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779191042; cv=none; b=TZtBz45gy2v6vwZrR4Qqhba1iQPofEodzd+je6mHluei6Yg+YVukeSlBcPGS2YSQybw51VzzyK4cXruckwcqBhQkTcAxrCDpPtWKLDQrhI0CIFW8h730vuXSKRGCW6vYij5ZqAV1/TA4FUxtB6/XXElKj6M6J4Y+0MpZ9qBr39k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779191042; c=relaxed/simple; bh=FBz9tT367NOveFkgTXJIp3fcfL4+cF9VuG0RohZV40s=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=TTlb0YhX9eiW9jxckphN1fhWasrLKlCy8ZzXPr/9ErMJciL0QKfbPHjVnu4mk9BH2PMSnL1z3tLsDoK2KkRR9U4i8ZOGJomKG78+H0w8at5NGczAX23JS6O8VRpBxmdCIAYTiW3keImwHAJUgm3DuUAe0PTqoKZDYLVNmic1GFU= 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=FJkXRWCi; arc=none smtp.client-ip=209.85.219.74 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="FJkXRWCi" Received: by mail-qv1-f74.google.com with SMTP id 6a1803df08f44-8aca172588cso100576536d6.0 for ; Tue, 19 May 2026 04:44:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1779191040; x=1779795840; 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=Nthh0wOYkbgoOXenxGs1OlmA1njW0yrnzAWO8T7rE7o=; b=FJkXRWCiJBDPDU0YAxQ3lkoNNIiqGruSlgdnAF0H3RVbIQeJJYshWnYh3+3oOSJCMm 4P2xVKrlcq9iqLICYycG6mDRtq+2cbeCnObmIVwa03m0zJEA+7fUXDRN5ms8kZN948V0 hvk09yOo5tbtu9gktUeoqbJVuwTdGZ4CU10SxBCc0PPECbbwbLihVt9Ln8tGUNNtiubs kjufUIWgAtUxCvjKMke2XdJOdSJElPz/UIiCO7FmlfukowkZ2Qr65AU1emc8d9H2QRUP 9ikYGO/RDtOSifX5RB3akUjL24lVhVl88ZyQEGweY5MR6WW/hitG7kgL1N+tLAc6x2EB b3Tw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1779191040; x=1779795840; 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=Nthh0wOYkbgoOXenxGs1OlmA1njW0yrnzAWO8T7rE7o=; b=bsW9FeM6nVJrZ3J8nnDirYXkbReuOXmzjx8ny1JBrgf5qUtQKsAGCUADEoQgjgwwL/ MrZP3heChscnEQm6DGnZtpVi1AQMmG4OpYMsqjdtzteyqy+3g0qK1RKd0fcovhCnNkKs eGAe5nn7GZOPKZmMKo+2Bpr86kQ6dcdQZl+YTdCjypmt27JtbmpUZkgogmX7l2LrzLLw aqE05dVYhodAwbDxDlLKk9sxnYTk8uO2xlVCkHgzaOCxwT0Z6+u2kTd39pWAgre0Kjem MD9LMkv0HIykmTBUhxW+1MswkFOV39atYK0eRfpNcnZutMzDjHdMoGe4LtOskj4mdwne g4vQ== X-Forwarded-Encrypted: i=1; AFNElJ93ES1hwvinRVPbFPfQOs/VK9mRauEGk/spsdylZ7jUJrng3vfxBMtL/XrJsQMeCrkorOFbgig=@vger.kernel.org X-Gm-Message-State: AOJu0YxGr62L+/dCSonj534MziMiGJvgRTHgkpvLbtcSiT9/+ifcgBjQ 82t5Ze4Lz0K/KLPVTlDXubrlfZD5UJ70tOMutYVWYgBqG4id+iLFwnXmXdOkwgoM13PvTYYsR/U BaxKRqBmP2UEWiw== X-Received: from qvcc10.prod.google.com ([2002:a05:6214:224a:b0:8b7:a795:d3f4]) (user=edumazet job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6214:4b04:b0:8be:3da0:bba7 with SMTP id 6a1803df08f44-8ca0f671f23mr341421916d6.16.1779191039958; Tue, 19 May 2026 04:43:59 -0700 (PDT) Date: Tue, 19 May 2026 11:43:55 +0000 In-Reply-To: <20260519114355.2769474-1-edumazet@google.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260519114355.2769474-1-edumazet@google.com> X-Mailer: git-send-email 2.54.0.563.g4f69b47b94-goog Message-ID: <20260519114355.2769474-3-edumazet@google.com> Subject: [PATCH v2 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: Simon Horman , Kuniyuki Iwashima , 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 --- v2: move the ASSERT_RTNL() in rtnl_fill_ifinfo() net/core/rtnetlink.c | 72 ++++++++++++++++++++++++++++++++------------ 1 file changed, 52 insertions(+), 20 deletions(-) diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c index ae0254f19178735b2805a8189e81a960a49b2858..68cd2238ee170f44841caf47c86ef48303a3d15e 100644 --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -2068,7 +2068,6 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb, struct nlmsghdr *nlh; struct Qdisc *qdisc; - ASSERT_RTNL(); nlh = nlmsg_put(skb, pid, seq, type, sizeof(*ifm), flags); if (nlh == NULL) return -EMSGSIZE; @@ -2091,6 +2090,7 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb, if (ext_filter_mask & RTEXT_FILTER_NAME_ONLY) goto end; + ASSERT_RTNL(); if (tgt_netnsid >= 0 && nla_put_s32(skb, IFLA_TARGET_NETNSID, tgt_netnsid)) goto nla_put_failure; @@ -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