From nobody Mon Nov 25 11:47:16 2024 Received: from m16.mail.163.com (m16.mail.163.com [220.197.31.5]) by smtp.subspace.kernel.org (Postfix) with ESMTP id A95B1142E86; Mon, 28 Oct 2024 06:25:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=220.197.31.5 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730096715; cv=none; b=vGo3cPzZMlQJy8nTthJfKmVdFvZan/lzLKMRAK+FmFYkxyurSBoLFLEKe50W8FPQpY63NN7Cq/SJNZH11pTOHdODcJpBMOMPf/IY79kmG7FbI5YOYtoKxJ8ExHHVbPkTRui5VIS5NobGRYf7tTfahpQWx1nhtLBp/4KdtppXHEM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730096715; c=relaxed/simple; bh=V4+xfa194CBFp5q3Inlgr8aVzHzK5NZ5xiP0OuJVVKQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=tFcTPqlVjRvZitxhuMgDJe++SqedsRKVcBjoA7vOkHxx0Bxc5YQXxi7H341Dv0cOG2nWTUhxFq44hXqbjD3Kh0QL3OPZMs6pkSbSm6ONykfuS3AEWPzBCc8T2I8Mw7qAsv6WQqqJhhB6fAOPU1KSQPCLdVBD153gdWLcVMuWr0o= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com; spf=pass smtp.mailfrom=163.com; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b=M5UadF+U; arc=none smtp.client-ip=220.197.31.5 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=163.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b="M5UadF+U" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=From:Subject:Date:Message-ID:MIME-Version; bh=MnCJU 2J3pJ6fwUvA85VlD1sdw0N2m8tj2xG8I7tc5pg=; b=M5UadF+UJiIiYXpJuOvA8 xaDhrgCah03hkeerzByUdAGNoXhmsfL8ZZrSNMUl8QvFgc5j+TORgOK29Zv6zd7N +BTr36Wb69mVOViai8nsvVF2zZCEVrMD6pLmaayOlAJmj8JqmnCHyvauyO5F70Hr VStn42LJUl6OPJejqzegxI= Received: from localhost.localdomain (unknown [47.252.33.72]) by gzga-smtp-mtada-g0-0 (Coremail) with SMTP id _____wDnDzAfLh9nUZxTBw--.19283S2; Mon, 28 Oct 2024 14:24:36 +0800 (CST) From: mrpre To: xiyou.wangcong@gmail.com Cc: edumazet@google.com, jakub@cloudflare.com, davem@davemloft.net, dsahern@kernel.org, kuba@kernel.org, pabeni@redhat.com, netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, mrpre Subject: [PATCH v2] bpf: fix filed access without lock Date: Mon, 28 Oct 2024 14:23:34 +0800 Message-ID: <20241028062334.35488-1-mrpre@163.com> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20241021013705.14105-1-mrpre@163.com> References: <20241021013705.14105-1-mrpre@163.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: _____wDnDzAfLh9nUZxTBw--.19283S2 X-Coremail-Antispam: 1Uf129KBjvJXoW7Kr1rCFy7WFWfXr43KFy5CFg_yoW8CFy3pF ZrGw109a1DJFWDAr4vyFZ7JF13W3ySka4Uurn5uayfArsI9r1fKFWvkw4ayF1YgF4vvw1a qrWjqr1q93WDA3JanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x0piX_-PUUUUU= X-CM-SenderInfo: xpus2vi6rwjhhfrp/1tbiDxyGp2cfJbW6RwAAsn Content-Type: text/plain; charset="utf-8" The tcp_bpf_recvmsg_parser() function, running in user context, retrieves seq_copied from tcp_sk without holding the socket lock, and stores it in a local variable seq. However, the softirq context can modify tcp_sk->seq_copied concurrently, for example, n tcp_read_sock(). As a result, the seq value is stale when it is assigned back to tcp_sk->copied_seq at the end of tcp_bpf_recvmsg_parser(), leading to incorrect behavior. Due to concurrency, the copied_seq field in tcp_bpf_recvmsg_parser() might be set to an incorrect value (less than the actual copied_seq) at the end of function: 'WRITE_ONCE(tcp->copied_seq, seq)'. This causes the 'offset' to be negative in tcp_read_sock()->tcp_recv_skb() when processing new incoming packets (sk->copied_seq - skb->seq becomes less than 0), and all subsequent packets will be dropped. Signed-off-by: Jiayuan Chen --- V1 -> V2: add more commit message to describle the issue --- net/ipv4/tcp_bpf.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c index e7658c5d6b79..7b44d4ece8b2 100644 --- a/net/ipv4/tcp_bpf.c +++ b/net/ipv4/tcp_bpf.c @@ -221,9 +221,9 @@ static int tcp_bpf_recvmsg_parser(struct sock *sk, int flags, int *addr_len) { - struct tcp_sock *tcp =3D tcp_sk(sk); + struct tcp_sock *tcp; + u32 seq; int peek =3D flags & MSG_PEEK; - u32 seq =3D tcp->copied_seq; struct sk_psock *psock; int copied =3D 0; =20 @@ -238,7 +238,8 @@ static int tcp_bpf_recvmsg_parser(struct sock *sk, return tcp_recvmsg(sk, msg, len, flags, addr_len); =20 lock_sock(sk); - + tcp =3D tcp_sk(sk); + seq =3D tcp->copied_seq; /* We may have received data on the sk_receive_queue pre-accept and * then we can not use read_skb in this context because we haven't * assigned a sk_socket yet so have no link to the ops. The work-around --=20 2.43.5