From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-dy1-f200.google.com (mail-dy1-f200.google.com [74.125.82.200]) (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 099284078FF for ; Mon, 5 Oct 2026 21:40:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.82.200 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791236418; cv=none; b=P8DxmYwifhCp/qKBcRHsulu70TlnR7W5yeBCRJ/ontPI1lEHacxu81gd4Kk5xQA5+hHEPEWZ8Fm/sSKnV/ocbS/ko2DmdaQu5UhJp+OqUZihBKCCTpGhf4nnP8sMmZ9uPTdK9FMAMLtBK/2RQQQW4g5EfWcU8C8WZWMs8gpuXuQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791236418; c=relaxed/simple; bh=hZ72QiBX9jr5EaifXwSBZkKDY7OHjW1ZuK993j0M4KI=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=Fhs5hwbQDShkI6M+WwD3Dj2vNWJS3yU+1uEt9lDRaMtZ82CgIi5eNkdeDcF2QXG5xtSMN/z/Qeu43wK8yhSqQyg1oxdN6+ctBXqwmgIlWvSnR+iL0HmRG2OS3LJNUzrXdTGXZFpCCdmj5pckcik4uOH6uaxEBm9ipasp+/FqIHo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--kaifengw.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=DS6qLBsK; arc=none smtp.client-ip=74.125.82.200 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--kaifengw.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="DS6qLBsK" Received: by mail-dy1-f200.google.com with SMTP id 5a478bee46e88-33c35f5ca6cso4391909eec.1 for ; Mon, 05 Oct 2026 14:40:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1791236416; x=1791841216; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:mime-version:date:from :to:cc:subject:date:message-id:reply-to:content-type; bh=tdubeg5f9M8doijKMCBDu9RikmQV/qCGF+3oJYA6B3A=; b=DS6qLBsK44y0c0q/ywZMvw1KaXkNzptjHeuvauTSUwPSwAXkkB+xPqcSdkauabnh3D 8Alnrukeufrk8SnpANsr94mKRg3LUTLK+qbM8lUlp47whmL32E52Q+L3TqHrM5qMcVE4 IpZuU6lmWuQfizwM/CGtmRMD20zfqo1ABY8Q+yskFR95cfliz+NSrReMV25YGdB98nPj gfCeqlnLOjrAYt5fm4yYOfDTBg1daD1cONxXrnBqbmsdy4MutlT7oYRughhoLtYpmrZU Ot8F4BqeQ0WpBlQBp1dTZHMcg3fR8exopOCWYRW2w5n1uZh1/AZhgIdP/yIxC7jzY9z/ RqCg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1791236416; x=1791841216; h=content-type:cc:to:from:subject:message-id:mime-version:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=tdubeg5f9M8doijKMCBDu9RikmQV/qCGF+3oJYA6B3A=; b=jMUKadYx/lKhDyvxLIxeMq+pHzOe379UYLv6tJt4NQ6qg3m6yZE+kSSObqGWp0LbXR 132v17lza39NZ3dle2mal4NnAjjBJm/ExrrZaEm+C2mxXcyZGcMMBzHq2XKs8wg8oN/m YYwvKZFZP3zbHALEEz1goSrQvudblWg4P2JXrGWyq08uw7pV8NY+i8QsKiN26km9lr7R VfQaU0RRDiBSUO3ZNrFQOJY08Wc2cdS15A9ue4XNZQMTS0hceMM5ZmKQ+4mYYHMSzSek 1ZDOUZR2/DnbOwpJQw6pmrhQk7y5jhVUuHciX/sAoig/f0uIXfAqT9xg6pBiS0vfVtlj Mhrw== X-Gm-Message-State: AFuF++nAYFj4+0Eog1VAdvhnvQhO4Gz79JKSrW3/7/+tVkb319CffgJx NG+/BmeTcew4eafKczXRfh77dDz6OYPNiNUgrzw5y0oJj3yzwG1wiy1Tx3Gjleu31+yboBbXhfM HKYW1vUUA3EIIFj/sg6pTsjKXPGvlOEC9o+CrfqCTDYTo4J/8HTBoNKr4lX3vN0W+yXRwkrz+WK pE5RK4mup+c98KkFnZu7BJt/eypi5cWz1fOq9F4wt5lese7dk= X-Received: from dycqw17-n2.prod.google.com ([2002:a05:7300:c011:20b0:33e:51c3:47b8]) (user=kaifengw job=prod-delivery.src-stubby-dispatcher) by 2002:a05:693c:41d4:20b0:341:c6ca:1df3 with SMTP id 5a478bee46e88-34f150bd707mr14349688eec.14.1791236415510; Mon, 05 Oct 2026 14:40:15 -0700 (PDT) Date: Mon, 5 Oct 2026 21:40:02 +0000 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.56.0.rc1.315.gc6ed9934b7-goog Message-ID: <20261005214002.3226574-1-kaifengw@google.com> Subject: [PATCH net] tcp: reject devmem tx with fastopen and repair From: Kaifeng Wang To: netdev@vger.kernel.org Cc: edumazet@google.com, ncardwell@google.com, kuniyu@google.com, davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, asml.silence@gmail.com, almasrymina@google.com, willemb@google.com, kaiyuanz@google.com, sdf@fomichev.me, linux-kernel@vger.kernel.org, Kaifeng Wang Content-Type: text/plain; charset="UTF-8" tcp_sendmsg_locked() enforces that devmem TX can only proceed if the zero-copy path is active and a valid dmabuf binding exists. However, subsequent branches in tcp_sendmsg_locked() can still intercept the message before it reaches the devmem zero-copy loop: 1. TCP Fast Open (MSG_FASTOPEN or DEFER_CONNECT): If TCP_FASTOPEN_CONNECT is set, the socket may have a valid dst with NETIF_F_SG (so zc == MSG_ZEROCOPY and binding is present), but tcp_sendmsg_fastopen() -> tcp_send_syn_data() will use copy_page_from_iter() to byte-copy from the iterator. Since iov_base represents dma-buf offsets rather than user virtual addresses, this misinterprets offsets as user pointers and copies arbitrary user memory into the SYN packet. 2. TCP repair mode: If tp->repair is enabled with TCP_RECV_QUEUE, tcp_send_rcvq() similarly calls skb_copy_datagram_from_iter(), byte-copying from the iterator. Neither path supports or makes sense for devmem transmission. Reject devmem sends if Fast Open or repair mode is active. This pre-existing issue was identified by Sashiko AI review on commit 125755776bc6 ("tcp: reject non zerocopy devmem tx") and has not been hit in production. Fixes: 125755776bc6 ("tcp: reject non zerocopy devmem tx") Fixes: bd61848900bf ("net: devmem: Implement TX path") Signed-off-by: Kaifeng Wang --- net/ipv4/tcp.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 87ef6d5cbfeb..225e758c194a 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -1169,7 +1169,9 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size) zc = MSG_SPLICE_PAGES; } - if (!sockc_err && sockc.dmabuf_id && (zc != MSG_ZEROCOPY || !binding)) { + if (!sockc_err && sockc.dmabuf_id && + (zc != MSG_ZEROCOPY || !binding || tp->repair || + (flags & MSG_FASTOPEN) || inet_test_bit(DEFER_CONNECT, sk))) { err = -EINVAL; goto out_err; } -- 2.56.0.rc1.315.gc6ed9934b7-goog