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 9079F440632 for ; Tue, 1 Sep 2026 16:02:49 +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=1788278570; cv=none; b=bzdH6rRVqucgkihbeBB0yweHjxez90FFSqIkTvFun2vkuJTgzoJuoJKhMCam/dCk7VwKzyb7gI6zu+c+a9/LJrhtnN2BrlZclxctrgsLs2BFKwO+NPYRUD40uO4qd6ztqaIo0g0QYjE+Z/7hYTT+socWmCxEYo9PB7yObFd7x2E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788278570; c=relaxed/simple; bh=APaayGAlAhe7lu0PqrAYKa5mg2lOo/Xj9CH7j3bHK5k=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=hpt8ZM+/Ve/QgRjRQxMBAn/hnncLH9Da/rz/1jBS+Qf80pHEObxIyr6fJhlIoWg5YfkPm3/yqCDQnfKeLOCbL6tGC5SM2uwRqI3gFRYwdHVw2m4GEtvV+rdCs3ab/aKqFXSyie00YUgyWKRmaMOOSNQ2wrQdCSKkyuENglnfKao= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=dj5OPlmu; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="dj5OPlmu" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A38021F00A3A; Tue, 1 Sep 2026 16:02:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788278569; bh=bmH151Bd/yBmFU+RPQ0IEaN8D17K7/Ylal2pl4QhZA4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=dj5OPlmuvmtTB0r94lkacC5L+RZXp8cN7x7TLA0dPAHENZUqfieHAd2oDbxAIsKec XaQgAMkc0PRLLTTWMNPmfFHVdNdofuBAgkxwE1Xya0BT1yXaPweqKRvHqHz83Gcl5E rZOE4pW/NZ1LR5J5k7VjQXBjVp1zElAkm388fb87QzjDNycagqNOirs9oCbiExlxLp sjygPcHpqgzmx9eWtuzqTfu0pMKk9FM/MnGyGUxPtHJXN3bJ52C5nYmUlk/MNjg2kZ NoBIUmDQkLiJtX/jq3x0AK5vSHi503+yyvE/UZEW77OZAIG2bAakthNIkx5oOtygX4 LhuEUaT3WUu/g== From: Sasha Levin To: stable@vger.kernel.org Cc: Eric Dumazet , Tangxin Xie , Jakub Kicinski , Sasha Levin Subject: [PATCH 5.15.y 2/2] vlan: fix skb_under_panic and races when toggling HW VLAN offload Date: Tue, 1 Sep 2026 12:02:46 -0400 Message-ID: <20260901160246.1284556-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260901160246.1284556-1-sashal@kernel.org> References: <2026083120-reunion-cadillac-38bb@gregkh> <20260901160246.1284556-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Eric Dumazet [ Upstream commit 447cbe95ebb95392b5d8f6a01c0556826919ce23 ] 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: Sasha Levin --- net/8021q/vlan_dev.c | 39 +++++++-------------------------------- 1 file changed, 7 insertions(+), 32 deletions(-) diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c index 63d55eab7227d..8309423e742dc 100644 --- a/net/8021q/vlan_dev.c +++ b/net/8021q/vlan_dev.c @@ -500,26 +500,6 @@ static const struct header_ops vlan_header_ops = { .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", }; @@ -573,14 +553,10 @@ static int vlan_dev_init(struct net_device *dev) 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; @@ -801,10 +777,9 @@ void vlan_transfer_features(struct net_device *dev, vlandev->gso_max_size = dev->gso_max_size; vlandev->gso_max_segs = dev->gso_max_segs; - 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; -- 2.53.0