From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 A48A54EF5E9; Mon, 31 Aug 2026 13:40:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788183648; cv=none; b=PhJSIb9ErnxAYRi0BcipP17ExhlyVAfcj+QcXLAJsxpzWIwmE3jCiSdcqcuk3YgPX/Z4K29p1iVhRsWk0jLNF2fgYpRTg+LYLiutZTYAPZTOxeTDbB3gXsd8yDw1XAJnMTC4ZJK1T0xEVm4CDBEOL3wFgMb2XfzoJz9uUVl9/MM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788183648; c=relaxed/simple; bh=sSWv46OOjOyn9mJ6O/VeH2cvZx0i36KW8VpBfdRH24g=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=mxGOglByXw9fJDyI9jkaSnq5yW5kSSK5cujlWWG7Qtj+7d7zDXp433iGgTyF6kvZkc36tbMfhQB3jgXMg+9Ms2QqXNHWOCrq/ebOaSzo0SIuxD/zBcEKeFTWnX4KKThTAyINYtS/qwMZqHIBclJkxdxMa1E/xNg6xhhgkVZr6BM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=LFTJFaS/; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="LFTJFaS/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E63291F00ACA; Mon, 31 Aug 2026 13:40:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788183645; bh=TiXZKkXVAfes1Q11RwAfhtVBpdYMF7duw5pQQ9K59NA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=LFTJFaS/Tq8Q6mzcdqQzi92pONxkONf1kH4HaJ1CIJFQ54W+alz/br6DHYiCgxxxh FDlJGcd37g4eNsdKyaZjMXHZWgB8+f7H2uskOOGYvtsVrGparZjnORFNJ4bYvI+YPY x28jegW6o4nkKox61lTHAfvYlNJwUu9gTNj5GWYQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Tangxin Xie , Eric Dumazet , Jakub Kicinski Subject: [PATCH 7.2 40/71] vlan: fix skb_under_panic and races when toggling HW VLAN offload Date: Mon, 31 Aug 2026 15:34:05 +0200 Message-ID: <20260831133401.285217721@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260831133359.055927882@linuxfoundation.org> References: <20260831133359.055927882@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet commit 447cbe95ebb95392b5d8f6a01c0556826919ce23 upstream. Toggling hardware VLAN TX offload (NETIF_F_HW_VLAN_CTAG_TX or NETIF_F_HW_VLAN_STAG_TX) on a lower device invokes vlan_transfer_features(), which dynamically changed vlandev->hard_header_len. This causes two issues: 1. Lockless TX paths (e.g. packet_snd in af_packet.c, ip6_finish_output2) read dev->hard_header_len without holding RTNL lock. Mutating hard_header_len dynamically under RTNL creates a data race where upper layers reserve insufficient headroom based on a stale hard_header_len, resulting in skb_under_panic when vlan_dev_hard_header() is called. 2. In addition, vlan_transfer_features() updated hard_header_len without updating header_ops, causing a mismatch between allocated headroom and header creation. Always setting dev->hard_header_len = real_dev->hard_header_len and dev->needed_headroom = real_dev->needed_headroom + VLAN_HLEN unconditionally ensures: - dev->hard_header_len remains 100% static and immutable at real_dev->hard_header_len, eliminating all dynamic runtime updates and data races on hard_header_len. - Upper layers allocating skbs via LL_RESERVED_SPACE() will always reserve sufficient headroom for software VLAN tag insertion (real_dev->hard_header_len + real_dev->needed_headroom + VLAN_HLEN). - vlandev inherits real_dev->needed_tailroom so underlying trailer/padding/ICV requirements are honored. - AF_PACKET SOCK_RAW network header offsets remain correctly aligned at real_dev->hard_header_len. - vlan_header_ops is used unconditionally. Note to stable teams: Make sure to backport these commits: e16e960d55a4 ("ipvlan: inherit needed_headroom and needed_tailroom from phy_dev") cef51860becd ("macvlan: inherit needed_headroom and needed_tailroom from lowerdev") Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: Tangxin Xie Closes: https://lore.kernel.org/netdev/99d678ae-c7b2-4b44-b534-b8320679deb3@h-partners.com/ Cc: # 3.19: e16e960d55a4: ipvlan: inherit needed_headroom and needed_tailroom from phy_dev Cc: # 3.19: cef51860becd: macvlan: inherit needed_headroom and needed_tailroom from lowerdev Cc: # 3.19 Signed-off-by: Eric Dumazet Link: https://patch.msgid.link/20260811085246.2267779-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/8021q/vlan_dev.c | 39 +++++++-------------------------------- 1 file changed, 7 insertions(+), 32 deletions(-) --- a/net/8021q/vlan_dev.c +++ b/net/8021q/vlan_dev.c @@ -502,26 +502,6 @@ static const struct header_ops vlan_head .parse_protocol = vlan_parse_protocol, }; -static int vlan_passthru_hard_header(struct sk_buff *skb, struct net_device *dev, - unsigned short type, - const void *daddr, const void *saddr, - unsigned int len) -{ - struct vlan_dev_priv *vlan = vlan_dev_priv(dev); - struct net_device *real_dev = vlan->real_dev; - - if (saddr == NULL) - saddr = dev->dev_addr; - - return dev_hard_header(skb, real_dev, type, daddr, saddr, len); -} - -static const struct header_ops vlan_passthru_header_ops = { - .create = vlan_passthru_hard_header, - .parse = eth_header_parse, - .parse_protocol = vlan_parse_protocol, -}; - static const struct device_type vlan_type = { .name = "vlan", }; @@ -580,14 +560,10 @@ static int vlan_dev_init(struct net_devi dev->fcoe_ddp_xid = real_dev->fcoe_ddp_xid; #endif - dev->needed_headroom = real_dev->needed_headroom; - if (vlan_hw_offload_capable(real_dev->features, vlan->vlan_proto)) { - dev->header_ops = &vlan_passthru_header_ops; - dev->hard_header_len = real_dev->hard_header_len; - } else { - dev->header_ops = &vlan_header_ops; - dev->hard_header_len = real_dev->hard_header_len + VLAN_HLEN; - } + dev->needed_headroom = real_dev->needed_headroom + VLAN_HLEN; + dev->needed_tailroom = real_dev->needed_tailroom; + dev->header_ops = &vlan_header_ops; + dev->hard_header_len = real_dev->hard_header_len; dev->netdev_ops = &vlan_netdev_ops; @@ -1029,10 +1005,9 @@ static void vlan_transfer_features(struc netif_inherit_tso_max(vlandev, dev); - if (vlan_hw_offload_capable(dev->features, vlan->vlan_proto)) - vlandev->hard_header_len = dev->hard_header_len; - else - vlandev->hard_header_len = dev->hard_header_len + VLAN_HLEN; + vlandev->needed_headroom = dev->needed_headroom + VLAN_HLEN; + vlandev->needed_tailroom = dev->needed_tailroom; + vlandev->hard_header_len = dev->hard_header_len; #if IS_ENABLED(CONFIG_FCOE) vlandev->fcoe_ddp_xid = dev->fcoe_ddp_xid;