From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f44.google.com (mail-pj1-f44.google.com [209.85.216.44]) (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 362913BD642 for ; Thu, 30 Jul 2026 08:30:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.44 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785400211; cv=none; b=tgwKGTFa5aDW0cUBIruFoCGtKhNqT0OBoXdCNCFQM2hRjTTvvgP4cvJtkUeautu/z4mI2lxfkTDd+3LBQXl6C6ox/QdQ/clF2E44tYXDyokCtaho3C0kmvmAjoNbFrVfw0WglyAl/0h1N61dMFa3WN7W1IGtm8qQCv9xckpf5pw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785400211; c=relaxed/simple; bh=2+lD755z7Rh4q3JmyL4x3OHtwEBfh1KbS7Y4miJd/mQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=TK1QCaaxg/ZpFQQpczY9331TZuSG49H2WmqAt80zaiXqndj83F1Lg+JIF2KmbOt4fbDvLAOH8RLQwTXK94QF0vJtoPL2bI95YgAU5aNgunZ+bSXlcKY125Xr3g6XUyXppfmY2/wo8dhoS2Wu53v2LW6vr1AboYiv0Y049X3ZPgE= 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=l7u8zbsv; arc=none smtp.client-ip=209.85.216.44 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="l7u8zbsv" Received: by mail-pj1-f44.google.com with SMTP id 98e67ed59e1d1-380f3c1b087so178585a91.3 for ; Thu, 30 Jul 2026 01:30:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1785400209; x=1786005009; 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=xg7bd++vUDfsPPAlCp93j183GeX7bX18Uk0d449Ghw8=; b=l7u8zbsvIUf2/XTNtBlklP921yLpZmeqaCiQE9jyzpHNbkbv8pM7PEVGtTd+vyMxZb DP5/E53eleoncuyxHLgsDpnlco2cOMuGbr8fDPsSTkylNJnslbGCXJa6jNQP2dFSD8W+ BdlFr8vEDKvdaouHsV7osvCv7IK1SyFHVQMuQqljww9Y/hPL40Uzt5ZETEjAFnaqFfea LKkT6rLzJXCTGExKxeZ0Cmf8bQIIf/nrmW7HngzT2DHfj50uS1jtzqzlDa5mSsSpq2yR Q/jdfQU4gtPe3NMfaWjq3O6o+YREZ4TE1wkDs4FMR/1k+MJbgRwLpAxgtf7kp3RBGfOG 65RQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1785400209; x=1786005009; 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=xg7bd++vUDfsPPAlCp93j183GeX7bX18Uk0d449Ghw8=; b=D2AEZVDbFe7OZPVaRBLiY1LW8ZV9PcoJRZhRaY2E8AIljtC0ZGMSQ7y+txytL3sN2B GKAi38POR7SLxXKCy9tzZAfvqiak6Pvm3oLMgYdH6JIlDRwYeHSxXxlwBRncNsUwX2IS pKaZ6ZL09UC52mjrLZdJvNXsAkTW5EH5+F2PQYHr0n4LmLeopsBZRoq2m57Opuc6S06K FiZqmzyScu+7X+VEqHosu1TBymxI/VF9NDlLoRlcWrnaFGzOjdVKGDOFW7rQGWtr8Ysq pEnwpQkGi0/WPmEDSPIno91Hgmrg/inGgyS5Y+NqsLPQxAqYLhTVL0M8S+KLvBuY8FVc eh9Q== X-Gm-Message-State: AOJu0YzcPHXeW0NUXNUh1IKzQsO203tWhTRMnx8vEjLggDHfttGjiW28 B4UpcSQAgik5gf0V5dg8zQI2Onq0TorwPSc4d2+KiRN6tCWMik38YF7U2Zljuw== X-Gm-Gg: AR+sD13Srk10YqjGibIi8zJ1tcIUGtDl2ZGWrc8934uYqYXW+nQvZrquYL/lBVQqNMi 4XHzs8kmABqjC0frXnidvbfbmKeMFwL5KKb438Ktzq7RaZq/PDoWWGyafyzdqZoy4RjKBpirpkl Cad7ytuNAOIv8prXhykeuqUl94RbWSCk1r7b2i9MuHrGuAL1urkMtOLpOckCAa7bfvhw+FA5ccL F5C6qrvxrO3H1uqFLrY5M6IRb9He39zaic2xxk8zefOHy0n0qiO83QT4Jn7LjfSrzMErsX6Zzmu f8Bd9+f0QWoTo3CfvGXekNzBPw87c+7Chp2Q7KDnhM0IYejR4lPHiOeu8fuw55xWU/oGMcjd3e8 bTWrrHq3EAqC+W7SMgPEYyeP+ovNFw+JuJfGIl1uIkFF26BnTU2/JG4USVrizu6HE3u57Ef03Ai RcnywdekYVS1WtF6NJ4NmQ1q+r6JcHqwDbMzfzRQvhzZy6gi5069T8R8NfAXvJPW8yUromMgp7C 59QBf/03IbrAWY1JRAAXsN+3V1ViekabhbptSmGwtwrD5qo8Ds= X-Received: by 2002:a17:90b:4d0c:b0:381:28e0:6248 with SMTP id 98e67ed59e1d1-38f9bd23f50mr2067858a91.1.1785400209431; Thu, 30 Jul 2026 01:30:09 -0700 (PDT) Received: from localhost.localdomain ([139.159.170.89]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-38f9b770e33sm664279a91.15.2026.07.30.01.30.01 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Thu, 30 Jul 2026 01:30:09 -0700 (PDT) From: Qihang To: netdev@vger.kernel.org Cc: willemdebruijn.kernel@gmail.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 , Willem de Bruijn Subject: [PATCH net v5 1/2] packet: use consistent hard_header_len in non-ring send paths Date: Thu, 30 Jul 2026 16:29:24 +0800 Message-ID: <20260730082925.93759-2-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: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 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 9981d637f8b5..e50e8abc1392 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)