From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f169.google.com (mail-pl1-f169.google.com [209.85.214.169]) (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 5C0063AD501 for ; Tue, 4 Aug 2026 09:32:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.169 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785835951; cv=none; b=CW94RCtbRbA/+yjs56ZudONUei8huavlfEVDBytVwEiacLSUzbgzUiJtHNic2Rbq7eWXxeJsg2B/Kh5ygAQBwuBhkfsmwAZ6dTUDjWnT3jkKZDQWfGo6u4GFQxhcax9oMite2Ijvsc2jzkVrajaywAZxUBYpx2pLtJDFecZ7u9c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785835951; c=relaxed/simple; bh=B9hksGm9ntRRj9QAGHsjEV4YR/Q7/10o0v3GbCpC97g=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=SVoQ37TKg96IafJ0A/G0dh/CJTM0RCyxb4gbliUqnPp4Gbn336X21GaDg2SK/ICWm8HSgsxdRVaMEcSNMpsrVZCyA29i2WAwHBCXaoGt7GyXTs6PowkXef1R0risBL/EvdkZcOXgWahh+s0UVFswQV/6kBFO9cn2TiiqHHVi5cU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=foX1r/kg; arc=none smtp.client-ip=209.85.214.169 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="foX1r/kg" Received: by mail-pl1-f169.google.com with SMTP id d9443c01a7336-2d01548ac96so5223835ad.3 for ; Tue, 04 Aug 2026 02:32:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1785835950; x=1786440750; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=/CQIRskVYtbOfiKczfu0y6F86/TMtPEfVhmtJ7xiMZw=; b=foX1r/kg8eYUxeKPru1VC6xZ8R9LGW4O6/BW8Jwu3542HU6bQrUhoRU0LlgGH64Mnj KYva5wpjCdMv0HNLltb3Fz33NNUotFZFL4noc7kYiJFq2+chP4Yk10vaRRNjWGJIhso7 mMYWwBDnaE187QeRPr9o27Pfk4SQV3Ei4X6vYy9lg3iswn8l1v4DwEHK72I7Iqh7pZ0b m0BbkYleiqOv6suehuf4WPacCfIx4K15oo5TZear9FML7Z8ebAlzL9DyufiSRqinxOgY AQg9QxnFp/p4AOCx0DNxuuyB6uhMHCmGUV96QlG621fIBQqWuB+zujHhB5Ls1I8T5qP8 cmuQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1785835950; x=1786440750; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=/CQIRskVYtbOfiKczfu0y6F86/TMtPEfVhmtJ7xiMZw=; b=bsPlb6zJZ43lHUzOoyb6HPuwj7NoGmhoSVS+ymlDbFbgEb+9A5L8Ik+i3BhpMdYYNV 7wyPyiaT2vezf76PFtGPrSvwxFaOAgZB4wMIzlokJOrU3NBYUl1RN2NjxU1TbitDob6C 54Yo4W1cj6Y5A/t+9iiqDD2NjEZ3ZQ7SfHaId7IQWOtRyxG+SMGd52C4yEiR5ekd4pAd DqWZl2mfCcMvWizSfbeiB2FJh2DCndgkK4EFLW1x1u7Jiq133/FCgi+HXH3W3vodXvxg dgG7pM0rKBoTQNzTCe57tO21Zdu/fciK0A1RHepJTkBNhJyW8RTf5wKHrQaQTfATG8QR qW8w== X-Forwarded-Encrypted: i=1; AHgh+Rptn8SIKJ2QPZ0dWTDMNpeMhpDrm0XHWDMi4NVLsGDbJYT3mu5ppksn30WFn2+AwiO3j8IeFp0=@vger.kernel.org X-Gm-Message-State: AOJu0YwnH6co4jknpJPwAsMVO4lqlKud0REhE9bEJjZZxfTmhpasHE1+ 3BRCV1CE3mAfr/2tNGMHW4/olhJQik8wwhQs28j9S8MMiZfmuY7zUI6m X-Gm-Gg: AR+sD11AxeHIClMQLElnN/7p0rzBFzNViRLfit7yXDr6GIVD97ZjB+BICqPeF09TYvc oO0wkBzf9afGGOAQmJMVcpIhvqT8ee1yM6eS9Lm2Zo9ntzoZx3kLqClWsAmyPd3cLMYxkhkoNuX +opi5QPfw0Mr5ORtLQ9emxnKAfz4wyKd9XQcR3SgM7yWXeBaQWsp1rjsOYrfVHStOem/uvltZas 7Ajx0cBSrtCh2+uRKBKhGYtu+JOYAf5rAfGtJaTUbUcle+vxgBjduDLo7ui0w/ByAW0fOOSNpgH XhjQF7ZuPVym8rych5YSpiQRvZwgSoGm36dac2q/dgePqw1CvPr3QsW9IjjDmSd3nAdZAb6RvPA lk92vVoyg7UXkWmwSsYEYiyYFsKbtKHcOHQ+cTfPzWL2e4IpTtTKDPpwZpaV9dQqdfaXlsGxpxH 4jVC6eRd/qjm2A9kk5SgbdAko5YHFE8tZxGyDbkeUU35SzE3blDn1d3Um2e9SGD5R+UrnlwiV/n +T934MpSoMq4f9Oh3OesqxqYa90WP9Duh7nAVtPakanNOXkgK4= X-Received: by 2002:a17:903:1aa3:b0:2cf:ca85:57e2 with SMTP id d9443c01a7336-2d05219bb79mr183170125ad.1.1785835949479; Tue, 04 Aug 2026 02:32:29 -0700 (PDT) Received: from localhost.localdomain ([139.159.170.67]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2d0aa49325bsm3478945ad.40.2026.08.04.02.32.25 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Tue, 04 Aug 2026 02:32:29 -0700 (PDT) From: Qihang To: netdev@vger.kernel.org Cc: willemdebruijn.kernel@gmail.com, willemb@google.com, daniel.zahka@gmail.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, stable@vger.kernel.org, Qihang Tang Subject: [PATCH net v6 2/3] packet: use consistent hard_header_len in non-ring send paths Date: Tue, 4 Aug 2026 17:32:18 +0800 Message-ID: <20260804093218.33952-1-q.h.hack.winter@gmail.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20260730082925.93759-1-q.h.hack.winter@gmail.com> References: <20260730082925.93759-1-q.h.hack.winter@gmail.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Qihang Tang packet_snd() reads dev->hard_header_len multiple times while allocating and constructing an skb. Device reconfiguration can change this value concurrently, for example through bonding device type changes. For SOCK_RAW, packet_snd() can save a larger value in reserve and later allocate headroom using a smaller value. Moving skb->data back by reserve then places it before skb->head, and the following copy from userspace can attempt an out-of-bounds write. packet_sendmsg_spkt() has the same issue because it calculates its reservation and header offset from separate reads before dropping the RCU read lock to allocate the skb. Add LL_RESERVED_SPACE_EX() for callers that already saved a header length. Read hard_header_len once in packet_snd() and use it for allocation and construction. In packet_sendmsg_spkt(), preserve the allocation-time value through the device lookup retry. The separate SOCK_DGRAM consistency problem between hard_header_len and header_ops->create is not addressed here. Fixes: b84bbaf7a6c8 ("packet: in packet_snd start writing at link layer allocation") Cc: stable@vger.kernel.org Signed-off-by: Qihang Tang Reviewed-by: Willem de Bruijn --- include/linux/netdevice.h | 6 ++++-- net/packet/af_packet.c | 26 ++++++++++++++++---------- 2 files changed, 20 insertions(+), 12 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 9a770eb823ce..8840b126979f 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -300,9 +300,11 @@ struct hh_cache { * We could use other alignment values, but we must maintain the * relationship HH alignment <= LL alignment. */ -#define LL_RESERVED_SPACE(dev) \ - ((((dev)->hard_header_len + READ_ONCE((dev)->needed_headroom)) \ +#define LL_RESERVED_SPACE_EX(dev, hlen) \ + ((((hlen) + READ_ONCE((dev)->needed_headroom)) \ & ~(HH_DATA_MOD - 1)) + HH_DATA_MOD) +#define LL_RESERVED_SPACE(dev) \ + LL_RESERVED_SPACE_EX(dev, (dev)->hard_header_len) #define LL_RESERVED_SPACE_EXTRA(dev,extra) \ ((((dev)->hard_header_len + READ_ONCE((dev)->needed_headroom) + (extra)) \ & ~(HH_DATA_MOD - 1)) + HH_DATA_MOD) diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index e75d2932475a..88674a6e868c 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -1953,8 +1953,9 @@ static int packet_sendmsg_spkt(struct socket *sock, struct msghdr *msg, struct net_device *dev; struct sockcm_cookie sockc; __be16 proto = 0; - int err; + int hard_header_len; int extra_len = 0; + int err; /* * Get and verify the address. @@ -1997,14 +1998,18 @@ static int packet_sendmsg_spkt(struct socket *sock, struct msghdr *msg, extra_len = 4; /* We're doing our own CRC */ } + /* Keep the allocation-time header length across retry. */ + if (!skb) + hard_header_len = READ_ONCE(dev->hard_header_len); + err = -EMSGSIZE; - if (len > dev->mtu + dev->hard_header_len + VLAN_HLEN + extra_len) + if (len > dev->mtu + hard_header_len + VLAN_HLEN + extra_len) goto out_unlock; if (!skb) { - size_t reserved = LL_RESERVED_SPACE(dev); + size_t reserved = LL_RESERVED_SPACE_EX(dev, hard_header_len); int tlen = dev->needed_tailroom; - unsigned int hhlen = dev->header_ops ? dev->hard_header_len : 0; + unsigned int hhlen = dev->header_ops ? hard_header_len : 0; rcu_read_unlock(); skb = sock_wmalloc(sk, len + reserved + tlen, 0, GFP_KERNEL); @@ -2034,7 +2039,7 @@ static int packet_sendmsg_spkt(struct socket *sock, struct msghdr *msg, err = -EINVAL; goto out_unlock; } - if (len > (dev->mtu + dev->hard_header_len + extra_len) && + if (len > (dev->mtu + hard_header_len + extra_len) && !packet_extra_vlan_len_allowed(dev, skb)) { err = -EMSGSIZE; goto out_unlock; @@ -2956,7 +2961,7 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len) int offset = 0; struct packet_sock *po = pkt_sk(sk); int vnet_hdr_sz = READ_ONCE(po->vnet_hdr_sz); - int hlen, tlen, linear; + int hard_header_len, hlen, tlen, linear; int extra_len = 0; /* @@ -2996,8 +3001,9 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len) goto out_unlock; } + hard_header_len = READ_ONCE(dev->hard_header_len); if (sock->type == SOCK_RAW) - reserve = dev->hard_header_len; + reserve = hard_header_len; if (vnet_hdr_sz) { err = packet_snd_vnet_parse(msg, &len, &vnet_hdr, vnet_hdr_sz); if (err) @@ -3018,10 +3024,10 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len) goto out_unlock; err = -ENOBUFS; - hlen = LL_RESERVED_SPACE(dev); + hlen = LL_RESERVED_SPACE_EX(dev, hard_header_len); tlen = dev->needed_tailroom; linear = __virtio16_to_cpu(vio_le(), vnet_hdr.hdr_len); - linear = max(linear, min_t(int, len, dev->hard_header_len)); + linear = max(linear, min_t(int, len, hard_header_len)); skb = packet_alloc_skb(sk, hlen + tlen, hlen, len, linear, msg->msg_flags & MSG_DONTWAIT, &err); if (skb == NULL) @@ -3037,7 +3043,7 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len) } else if (reserve) { skb_reserve(skb, -reserve); if (len < reserve + sizeof(struct ipv6hdr) && - dev->min_header_len != dev->hard_header_len) + dev->min_header_len != hard_header_len) skb_reset_network_header(skb); } -- 2.50.1 (Apple Git-155)