From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793211904; b=caIsfi4Gdc113qbQwcRnvHZxajwik5ggleiQrwwmfP4isgkNu+lezrvpcrUSr9dikGmF qGnioCKfQlW1Q4kP7colHBI1FrLnhxzY9MS3OjKNh2IcPbsaKhePikgW8wD+7uziKdoH6 7AsqpG+KvaHaB0f6AvoZZ5cujG++14NHARa0w8/XCOAZ1Qjfu0PKI2JC6N+A0KpD+DJ5M cLDE9cLsrrVS/ayy8GtqX5EhQQxpYXDmY5W7TWhK2uolZM8OqEz4IfhC7yUMaTBD5yPOO YV+/QhcE3nocEu2wHCIhGsCPyNBjoF91qrAWrp3d4DPJwayMSRFrytOdn1FBjKnzLSg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793211904; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=JLKxtmphp6PoBUr9vb6xryN/umL0LI8Fuxbk34/X8mc=; b=BBgFISyL8K/Ijxo5lDtld/peUMLAFS2Q1eO8u8dGLM0E9W6gpaAqN6zr2IBq97wLhgpr HTTctc0anxKg6tjeXWDQ0o0f0eze/RBGpS7VM19W4/V2PMjnVqgMSUwdW1/kIKBqDvco3 hzMW19paMRW+2+usZWvsL0oZXtaPDYXSb3rdJIKL85Bv7u7NlPfcyuhvRqxidBSc3xkk7 +1RWpk/xUiBWwkkI5v6O0ogjXgoX538T5834icSn52xBK/V/XVqSO33Yo9D4fv/dsOJVW OI3YIHymbgqTQj76n9xLzjNt5fdfAazlS3QIFsXFlXWu4c4JLQPgQnc2jREorIZKB3g== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=WlhsmOSr; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AB60D606A31A; Wed, 28 Oct 2026 18:25:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=WlhsmOSr Received: by smtp.kernel.org (Postfix) with ESMTPSA id 06B7F1F01825; Wed, 28 Oct 2026 18:25:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793211903; bh=JLKxtmphp6PoBUr9vb6xryN/umL0LI8Fuxbk34/X8mc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=WlhsmOSrhQCK5xQMuAZ7uYv8mpjPdzEWt0pU1/PIztFrPcG4mcsghGS50KrNQ2sIJ qAscEY0MDv5f5uN//qZwL7U+OD8HFf0XowP5f/90CQ4Wvy1ikW94bBl5mxest7l4LO t0cRQaeldIvZQYFmHYIY1V+UU9InaxAMY7c4a2sI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Aswin Karuvally , Bryam Vargas , Alexandra Winter , Jakub Kicinski Subject: [PATCH 5.15 514/571] net/iucv: fix the recvmsg window update Date: Wed, 28 Oct 2026 18:01:01 +0100 Message-ID: <20261028170020.225607170@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028170008.009143722@linuxfoundation.org> References: <20261028170008.009143722@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Bryam Vargas commit fa5acd038ea657ad5033713d6916214cbd349151 upstream. iucv_sock_recvmsg() sends the HiperSockets-only AF_IUCV_FLAG_WIN without testing the transport, so on a classic z/VM socket iucv_send_ctrl() sizes the skb through a NULL iucv->hs_dev. SO_MSGLIMIT accepts 1, so msglimit / 2 is zero and one recvmsg() on its own socket is enough for an unprivileged process to take a spurious disconnect. It also calls iucv_send_ctrl() under spin_lock_bh(&message_q.lock), which allocates GFP_KERNEL inside a section the code treats as atomic. Sending outside that lock lets two recvmsg() reach afiucv_hs_send() at once, where msg_recv is sampled for the advertised window and subtracted after dev_queue_xmit() -- and sendmsg reaches that counter under lock_sock() while recvmsg holds no socket lock, so both can subtract the same value, the counter goes negative and the credit reaches the peer twice. Test the transport, claim the credit with atomic_xchg() after the last error exit and hand it back if the transmit fails, and send once the lock is dropped. Fixes: 3881ac441f64 ("af_iucv: add HiperSockets transport") Fixes: 238965b71b96 ("net/af_iucv: build proper skbs for HiperTransport") Cc: stable@vger.kernel.org Tested-by: Aswin Karuvally Signed-off-by: Bryam Vargas Reviewed-by: Alexandra Winter Link: https://patch.msgid.link/20260828-b4-disp-33fac0ed-v3-1-e6d061880ee0@proton.me Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/iucv/af_iucv.c | 42 +++++++++++++++++++++++++----------------- 1 file changed, 25 insertions(+), 17 deletions(-) --- a/net/iucv/af_iucv.c +++ b/net/iucv/af_iucv.c @@ -206,12 +206,6 @@ static int afiucv_hs_send(struct iucv_me phs_hdr->flags = flags; if (flags == AF_IUCV_FLAG_SYN) phs_hdr->window = iucv->msglimit; - else if ((flags == AF_IUCV_FLAG_WIN) || !flags) { - confirm_recv = atomic_read(&iucv->msg_recv); - phs_hdr->window = confirm_recv; - if (confirm_recv) - phs_hdr->flags = phs_hdr->flags | AF_IUCV_FLAG_WIN; - } memcpy(phs_hdr->destUserID, iucv->dst_user_id, 8); memcpy(phs_hdr->destAppName, iucv->dst_name, 8); memcpy(phs_hdr->srcUserID, iucv->src_user_id, 8); @@ -246,13 +240,22 @@ static int afiucv_hs_send(struct iucv_me } skb->protocol = cpu_to_be16(ETH_P_AF_IUCV); + /* Claim the receive credit here, not while building the header: every + * way this frame can be dropped has now been ruled out, so the window + * is zeroed only for as long as the transmit itself takes. + */ + if (flags == AF_IUCV_FLAG_WIN || !flags) { + confirm_recv = atomic_xchg(&iucv->msg_recv, 0); + phs_hdr->window = confirm_recv; + if (confirm_recv) + phs_hdr->flags = phs_hdr->flags | AF_IUCV_FLAG_WIN; + } + atomic_inc(&iucv->skbs_in_xmit); err = dev_queue_xmit(skb); if (net_xmit_eval(err)) { atomic_dec(&iucv->skbs_in_xmit); - } else { - atomic_sub(confirm_recv, &iucv->msg_recv); - WARN_ON(atomic_read(&iucv->msg_recv) < 0); + atomic_add(confirm_recv, &iucv->msg_recv); } return net_xmit_eval(err); @@ -1241,6 +1244,7 @@ static int iucv_sock_recvmsg(struct sock struct iucv_sock *iucv = iucv_sk(sk); unsigned int copied, rlen; struct sk_buff *skb, *rskb, *cskb; + bool send_win = false; int err = 0; u32 offset; @@ -1333,16 +1337,20 @@ static int iucv_sock_recvmsg(struct sock if (skb_queue_empty(&iucv->backlog_skb_q)) { if (!list_empty(&iucv->message_q.list)) iucv_process_message_q(sk); - if (atomic_read(&iucv->msg_recv) >= - iucv->msglimit / 2) { - err = iucv_send_ctrl(sk, AF_IUCV_FLAG_WIN); - if (err) { - sk->sk_state = IUCV_DISCONN; - sk->sk_state_change(sk); - } - } + if (iucv->transport == AF_IUCV_TRANS_HIPER && + atomic_read(&iucv->msg_recv) >= + iucv->msglimit / 2) + send_win = true; } spin_unlock_bh(&iucv->message_q.lock); + + if (send_win) { + err = iucv_send_ctrl(sk, AF_IUCV_FLAG_WIN); + if (err) { + sk->sk_state = IUCV_DISCONN; + sk->sk_state_change(sk); + } + } } done: