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=1793207693; b=b9aS5CtXPxG5k2V4dKgbDB3Bc2NliAxOvC5IsPKpslNZJFc4w0TcUFhLricGcRPZSez+ ulJgAmjOaptsFSp+CJQ8FWcTs719z5ayy3RpUZvbFrY3taRKQsYjYFQLdAETJR44paJYM 7LWDxrOKhY7rNXV9DRJtypYaXm3CrGuvtWB6bXCw4oUI8JPbHdXOINOci5ctF3JE+dqRb cvdRJNhBdY1YRmjk9JVRIpwFXOcxHVs4mNrG1QomA+3fGs7e/3oO7ubGTd2n5cHUPUHlm ViYMB7HrbMUel0Vv7ch8ZP/u4CrWtOSRE4TodteYypNwauf+WZWWPEsP6tRm0alpksQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793207693; 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=yrdVzTFes7MdIOu5TKHdp13E5rhiHIrrVtkvHFsydIw=; b=NEqLhIiWfKALrGne20DPwAhFD41AL23nqn7C3GEhl0iCz6FH0Wk+oz8YXwsaH2iWlhiq B2Zoov9p++b1G0kY6A33PXZkI6V3rj3+8jDqCT0N8LcDm4NFlcrCeFkTNipBak/GchrXz 1vGrpBkH1s4ZnObh4xZ5CrQIi05bM0WijhrVx9M2gSLmboXd4oaXhpOUuE2jxZUzH3h2k 4220u+gKCIfwXNDYY+otUPqg/lJ5AID2OpnvtB7N0DoC1r9qa+brt14LKqA89rdxD4h7G o1NfaaTBeBMaDkwTt58GvSe4iDawWYRkFJ9lkw7dnAT5kQ0Kvr5wk+V7EJcVblIp53w== 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=JVqyas3K; 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 54112606A31C; Wed, 28 Oct 2026 17:14:53 +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=JVqyas3K Received: by smtp.kernel.org (Postfix) with ESMTPSA id A1B851F01825; Wed, 28 Oct 2026 17:14:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793207693; bh=yrdVzTFes7MdIOu5TKHdp13E5rhiHIrrVtkvHFsydIw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=JVqyas3KIK+eduen0SiyFTjsI5l6s34JILSnaShEiVFTuWG7bwsS0QAp1VIM9s9W6 l4jhpqxOx/QsBjvSsn8LWxDYJveJj9rqapyCubdk8iRVvXyapkpxQVT2/oxUX27XmG MRdcmI8BYD1dQ9B6gI/y89PfAxrJQsgNKEt64fIc= 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 6.12 106/247] net/iucv: fix the recvmsg window update Date: Wed, 28 Oct 2026 17:58:29 +0100 Message-ID: <20261028165949.907161466@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028165947.349197979@linuxfoundation.org> References: <20261028165947.349197979@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 6.12-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 @@ -207,12 +207,6 @@ 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); @@ -247,13 +241,22 @@ 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); @@ -1237,6 +1240,7 @@ 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; @@ -1327,16 +1331,20 @@ 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: