From nobody Mon Nov 25 11:16:38 2024 Received: from m16.mail.163.com (m16.mail.163.com [220.197.31.5]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 8A5D918DF7D; Mon, 28 Oct 2024 06:53:15 +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=1730098399; cv=none; b=c4qfNBn5j51yoL+3EXdu9Efx3YfikviUeoTht9JpPuVP2EPZjhiQnfGwFJlwZuCpGwD5uQPUR8rJK8kVftuumO0ugZ/0owA67gJ1bRVTHigBw3TlVBk5mTIUngat7fw9gIbIK1Fy71XQxpXTjMr+u3vbCN0i62CJ3T5dbdXKZrs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730098399; c=relaxed/simple; bh=TogJYoeh0M9kdGAtiQR8MXVdXkWmgbpwWJ/bfasQLnM=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=BBEGgACj+d+DaypwAaZbfslVwI0YGlynAMMmvgSIma8nS9Cp9EVlP3Kw8keRAtDg4xcbARKWoZZTY4UZEJOQ4zhsuCODSN30396UO6A3EW3VaJhzrmqZuPUakVPxQMW7ByyhaUh40ux9u87gbzEdvKpSQ1ggOu0vBgHeQ1obTYI= 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=K0RhwyT9; 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="K0RhwyT9" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=From:Subject:Date:Message-ID:MIME-Version; bh=gb2og vjqOAk5QavOCwc2NuFRUeYMEbkQL5DGyoyp6jw=; b=K0RhwyT9lrnEBzG7oLml+ KHV8RdDgoO1TjUfU42azWbIZFsM1SSSTv0a1OF6BF+FKZszOxxt7Q624XnwVr7U6 L+Cbq9HXA1j1cUi8I2obcPI0zghGuzLNxbxo7nFeFLPrWGqTVmcmiVgmV/SvKe9C Z2GR1sWy0TIGMQXECzDS1w= Received: from localhost.localdomain (unknown [47.252.33.72]) by gzga-smtp-mtada-g0-0 (Coremail) with SMTP id _____wDn70W0NB9nqv9XBw--.5137S2; Mon, 28 Oct 2024 14:52:42 +0800 (CST) From: mrpre To: xiyou.wangcong@gmail.com Cc: yonghong.song@linux.dev, john.fastabend@gmail.com, 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 14:52:26 +0800 Message-ID: <20241028065226.35568-1-mrpre@163.com> X-Mailer: git-send-email 2.43.5 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: _____wDn70W0NB9nqv9XBw--.5137S2 X-Coremail-Antispam: 1Uf129KBjvJXoW7Kr1rCFy7WFWfXr43KFy5CFg_yoW8ZrWxpF ZrGw109a1DJFyDAr4vyFZ7JF13u3ySka4Uurn5WayfArsI9r1SgFWvkw4ayF1YgF4vv3Wa qrWYqr1q93WDAwUanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x0piX_-PUUUUU= X-CM-SenderInfo: xpus2vi6rwjhhfrp/xtbBDx2Gp2cfJFjVrQACsN 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 v1: https://lore.kernel.org/bpf/Zx1S9vf2i7O+BNE+@pop-os.localdoma= in/T/ --- 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