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Mon, 24 Aug 2026 12:58:40 +0000 (GMT) Received: from [9.224.90.36] (unknown [9.224.90.36]) by smtpav03.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 24 Aug 2026 12:58:40 +0000 (GMT) Message-ID: <732e3384-34a6-4309-b3ae-a8f3eccc7dad@linux.ibm.com> Date: Mon, 24 Aug 2026 14:58:40 +0200 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net v2 3/3] net/iucv: send the window update outside message_q.lock To: sashiko-reviews@lists.linux.dev, Bryam Vargas Cc: Vasily Gorbik , Christian Borntraeger , Heiko Carstens , Alexander Gordeev , linux-s390@vger.kernel.org References: <20260821-b4-disp-3a6e8695-v2-0-37597ff723a8@proton.me> <20260821-b4-disp-3a6e8695-v2-3-37597ff723a8@proton.me> <20260822111737.8DB721F000E9@smtp.kernel.org> Content-Language: en-US From: Alexandra Winter In-Reply-To: <20260822111737.8DB721F000E9@smtp.kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: 3vD741B9jDb-JhKtm3kEK5dH6uvXLQTQ X-Proofpoint-Spam-Info: AW1haW4tMjYwODI0MDEwNSBTYWx0ZWRfX/71rpmWQdB40 sWMC6CbmMEHWIWO3gHUv5Nwr+2cAKsEuovRFA2nlLsKyaUamdJ/IbU5JB9xq2cSnpgJ0+P/cYPs RKUJtv9dhUoX355rR3gj9HTq4QbPbqw= X-Proofpoint-GUID: 3vD741B9jDb-JhKtm3kEK5dH6uvXLQTQ X-Authority-Analysis: v=2.4 cv=JZyMa0KV c=1 sm=1 tr=0 ts=6a8c4007 cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=VwQbUJbxAAAA:8 a=UJCqotb1N0z-pNp_86gA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODI0MDEwNSBTYWx0ZWRfXwhax+VZfa/vW 4RHdZYrYixLYxL0Ve6z9+7Z0fwEoZztBIEi22A5gTog6SC1snNm7vrZIOwIjx6rMNBw9McVWcAj ptHRWgBQ87s3jd5NEwHrPnCLUsNftAi2AZaSStu428i4yHBpkCWIxa97I78E9I1I94MoY2GRPzp A1bDcebs7Boch1mijudFUJa8U7eEa88yxW0MripkDvyebmp8d2MEBcml6hnKbr5mmYcfnc6TXgm dQCJrenUxrKOFhhYFeuUHLshgjZi9fAErFhDWG+CeTay6iXbQLzf7lwiUE3iZ9Homxy9z6pvrf3 UCN/3sR55PmZABL2U9KasVwWPu8f0KN9qdL83GBCUKwb3CFEQQPMh7KUuxTGbGkOYW2EPuzNjiz VyZlp+h8o+J58V8IkmhcKxc6z3wSNTdl5MwwwK6r1+TV+OKRP1KHq5R5ztWIktqDiwmfKffGdXI w3kIfgBf//nh9dt4Nzg== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-24_03,2026-08-24_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 clxscore=1015 adultscore=0 priorityscore=1501 impostorscore=0 malwarescore=0 bulkscore=0 lowpriorityscore=0 suspectscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608240105 On 22.08.26 13:17, sashiko-bot@kernel.org wrote: > Thank you for your contribution! Sashiko AI review found 4 potential issue(s) to consider: > > New issues: > - [High] Redundant concurrent window updates cause spurious socket disconnections due to transient errors. > - [High] Lockless modification of `sk->sk_state` to `IUCV_DISCONN` in error path corrupts the socket state machine. > > Pre-existing issues: > - [Critical] Concurrent execution of `iucv_sock_recvmsg` and `iucv_sock_close` can lead to a NULL pointer dereference of `iucv->hs_dev`. > - [High] Lockless read-modify-write sequence on `sk->sk_shutdown` in `iucv_send_ctrl` permanently loses concurrent state updates. > -- > > --- Patch [3]: [PATCH net v2 3/3] net/iucv: send the window update outside message_q.lock --- > commit 38dc50c2f4dfcebf699da12476bf1a5fb529484e > Author: Bryam Vargas > > net/iucv: send the window update outside message_q.lock > > This patch moves the window update control message dispatch outside the > message_q.lock in iucv_sock_recvmsg(). It avoids sleeping in atomic context > since iucv_send_ctrl() performs a GFP_KERNEL allocation. A boolean flag is > used to defer the send until after the lock is released. > >> diff --git a/net/iucv/af_iucv.c b/net/iucv/af_iucv.c >> --- a/net/iucv/af_iucv.c >> +++ b/net/iucv/af_iucv.c > [ ... ] >> @@ -1336,15 +1337,18 @@ static int iucv_sock_recvmsg(struct socket *sock, struct msghdr *msg, >> iucv_process_message_q(sk); >> if (iucv->transport == AF_IUCV_TRANS_HIPER && >> 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); >> - } >> - } >> + 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); > > [Severity: High] > Because atomic_read(&iucv->msg_recv) is checked inside the lock, but the > counter is reset later inside afiucv_hs_send() without holding > message_q.lock, can multiple concurrent calls to iucv_sock_recvmsg() set > send_win to true and trigger redundant window updates? > No, because of the previous patch that is mentioned as a precondition. > If redundant updates are sent, could transient send buffer exhaustion cause > the socket to unintentionally hit the error path below and disconnect? I'm not sure I understand the question. But I think this works as designed.