From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C891537C106; Fri, 4 Sep 2026 05:59:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788501551; cv=none; b=dl8Yqh5j+EM46wPLXLDu1LmIpZ3WOxwAn6n0rS9Z/f/9llsocN5Dm93+NC4ks7ZHg1CQmqWRMtEqYze45f0CHI397KquvnXMurX9XidVlioi5iKrwy9oOQQsG1zL1hf/UWDlbtz+aPk0IECSia6G2ogVEChGNDeaZn3LalB5/Q8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788501551; c=relaxed/simple; bh=5t+8NFBbS6GBtEznlCbLTOMRWbLdN7LdNIbnfMD2Jis=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Y4WmpxKVGtT1cX3J2/qp8CQekaWSDrc5x4klzyGVX35mdvXUeYMt2pbCXUuEgrtSxRKaU/devZ9BGKSEarinwJwW4GIh5DGya5qqoMdyaPCvPh7bdgeKbtYgkLocLNg7rw0zW26isAXYYIQfXWk2Ofca0tlElxZzIXVsPXbiOiA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=twwBtU76; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="twwBtU76" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 016C71F00A3D; Fri, 4 Sep 2026 05:59:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788501549; bh=KERc2xMdI7yKsKyfFYGl/GmXVkHZyvJeVe58cL6tnmw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=twwBtU76+Q0DhFtNilIGSoPqf1dUhPODaRZQ8IwomlahqJnzVOzfOL5C2n3nEoxxu 9swfdk3z+ZAkPvCHmMrJheDjhoKkTAXk6LWRSVgUslNF0K92joTAjyw3olSrv/M3VM zyhGFofvPxHESHLr+YSV7fGfv4OVn2ZvKAH5YywQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Alexandra Winter , Jakub Kicinski , Bryam Vargas Subject: [PATCH 6.18 450/552] net/iucv: filter frames in afiucv_hs_rcv() by ingress device Date: Fri, 4 Sep 2026 07:00:07 +0200 Message-ID: <20260904045800.909081890@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260904045747.813364717@linuxfoundation.org> References: <20260904045747.813364717@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Alexandra Winter commit 80230a18c164a4b5bbc048fe2768b219ac17bc5a upstream. afiucv_hs_rcv() selects a socket from iucv_sk_list by matching four 8-byte name fields in the transport header alone. No check is made against the net_device the frame arrived on. This can cause a frame arriving on any netdev to be delivered to an AF_IUCV socket. Three problems follow. First, a frame arriving over HiperSockets can be delivered to a socket bound to the classic z/VM IUCV transport, which has iucv->hs_dev == NULL. iucv_sock_bind() takes the classic path whenever the requested userid matches iucv_userid, even on a guest that also has a HiperSockets device carrying the same identifier. The child socket created by afiucv_hs_callback_syn() for such a match inherits hs_dev = NULL and transport = AF_IUCV_TRANS_HIPER, so the first send() on it returns -ENODEV. The socket delivered to accept() is unusable. Second, a frame arriving on one netdev can be delivered to a socket bound to a different IQD device. Which can lead to - Accept-queue exhaustion (DoS) - Attacker-controlled peer identity in the child socket - Data injection into existing sockets - Fabric noise on the IQD fabric, where bogus replies are sent - killing established connections Third, all AF_IUCV sockets live in init_net, as iucv_sock_alloc() calls sk_alloc(&init_net, ...). But even frames arriving on netdev devices in a namespace can be delivered to an IUCV socket. So a process in an unprivileged user and network namespace holding only the CAP_NET_RAW capability valid within that namespace can send a raw ETH_P_AF_IUCV frame on its own lo device and have it matched against init_net sockets. Fix all three by skipping any socket whose hs_dev does not match the ingress device. A classic z/VM IUCV socket has hs_dev == NULL; the ingress dev is never NULL, so classic sockets are skipped automatically. An unbound HIPER socket also has hs_dev == NULL and is skipped. A bound HIPER socket is only reachable from the exact IQD device it was bound to. Because hs_dev is always a device in init_net (iucv_sock_bind() scans for_each_netdev_rcu(&init_net, ...) exclusively), a frame whose ingress device belongs to another namespace never matches any socket. Note that AF_IUCV over HiperSockets provides no per-connection authentication: no sequence numbers, no TLS, no nonce. The four name fields identifying a connection are exchanged in plaintext on the shared HiperSockets segment (VCHID). Any host on the same HiperSockets segment could spoof any frame type against an existing connection. That is a protocol-level property unchanged by this patch. The fix reduces the attack surface to peers present on the same HiperSockets segment. Fixes: 3881ac441f64 ("af_iucv: add HiperSockets transport") Cc: stable@vger.kernel.org Co-developed-by: Bryam Vargas Signed-off-by: Alexandra Winter Link: https://patch.msgid.link/20260821125501.3718748-1-wintera@linux.ibm.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/iucv/af_iucv.c | 2 ++ 1 file changed, 2 insertions(+) --- a/net/iucv/af_iucv.c +++ b/net/iucv/af_iucv.c @@ -2079,6 +2079,8 @@ static int afiucv_hs_rcv(struct sk_buff sk = NULL; read_lock(&iucv_sk_list.lock); sk_for_each(sk, &iucv_sk_list.head) { + if (iucv_sk(sk)->hs_dev != dev) + continue; if (trans_hdr->flags == AF_IUCV_FLAG_SYN) { if ((!memcmp(&iucv_sk(sk)->src_name, trans_hdr->destAppName, 8)) &&