{"id":2224793,"url":"http://patchwork.ozlabs.org/api/patches/2224793/?format=json","web_url":"http://patchwork.ozlabs.org/project/linux-cifs-client/patch/20260418172844.1333378-2-charsyam@gmail.com/","project":{"id":12,"url":"http://patchwork.ozlabs.org/api/projects/12/?format=json","name":"Linux CIFS Client","link_name":"linux-cifs-client","list_id":"linux-cifs.vger.kernel.org","list_email":"linux-cifs@vger.kernel.org","web_url":"","scm_url":"","webscm_url":"","list_archive_url":"","list_archive_url_format":"","commit_url_format":""},"msgid":"<20260418172844.1333378-2-charsyam@gmail.com>","list_archive_url":null,"date":"2026-04-18T17:28:43","name":"[1/2] ksmbd: fix active_num_conn leak when alloc_transport() fails","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"d65d0c56d3e0cfd2a4daf4f8ee18f47615108b35","submitter":{"id":93166,"url":"http://patchwork.ozlabs.org/api/people/93166/?format=json","name":"DaeMyung Kang","email":"charsyam@gmail.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/linux-cifs-client/patch/20260418172844.1333378-2-charsyam@gmail.com/mbox/","series":[{"id":500457,"url":"http://patchwork.ozlabs.org/api/series/500457/?format=json","web_url":"http://patchwork.ozlabs.org/project/linux-cifs-client/list/?series=500457","date":"2026-04-18T17:28:42","name":"ksmbd: connection accounting and session teardown fixes","version":1,"mbox":"http://patchwork.ozlabs.org/series/500457/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2224793/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2224793/checks/","tags":{},"related":[],"headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linux-cifs@vger.kernel.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256\n header.s=20251104 header.b=S4a7aoy3;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n (client-ip=2600:3c15:e001:75::12fc:5321; helo=sin.lore.kernel.org;\n envelope-from=linux-cifs+bounces-10900-incoming=patchwork.ozlabs.org@vger.kernel.org;\n receiver=patchwork.ozlabs.org)","smtp.subspace.kernel.org;\n\tdkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com\n header.b=\"S4a7aoy3\"","smtp.subspace.kernel.org;\n arc=none smtp.client-ip=209.85.214.176","smtp.subspace.kernel.org;\n dmarc=pass (p=none dis=none) header.from=gmail.com","smtp.subspace.kernel.org;\n spf=pass smtp.mailfrom=gmail.com"],"Received":["from sin.lore.kernel.org (sin.lore.kernel.org\n [IPv6:2600:3c15:e001:75::12fc:5321])\n\t(using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)\n\t key-exchange x25519 server-signature ECDSA (secp384r1) server-digest SHA384)\n\t(No client certificate requested)\n\tby legolas.ozlabs.org (Postfix) with ESMTPS id 4fyf0g3tWlz1yGt\n\tfor ; Sun, 19 Apr 2026 03:30:43 +1000 (AEST)","from smtp.subspace.kernel.org (conduit.subspace.kernel.org\n [100.90.174.1])\n\tby sin.lore.kernel.org (Postfix) with ESMTP id 5223B300515F\n\tfor ; Sat, 18 Apr 2026 17:30:40 +0000 (UTC)","from localhost.localdomain (localhost.localdomain [127.0.0.1])\n\tby smtp.subspace.kernel.org (Postfix) with ESMTP id 0B06932C8B;\n\tSat, 18 Apr 2026 17:30:38 +0000 (UTC)","from mail-pl1-f176.google.com (mail-pl1-f176.google.com\n [209.85.214.176])\n\t(using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits))\n\t(No client certificate requested)\n\tby smtp.subspace.kernel.org (Postfix) with ESMTPS id CC66A18C2C\n\tfor ; Sat, 18 Apr 2026 17:30:36 +0000 (UTC)","by mail-pl1-f176.google.com with SMTP id\n d9443c01a7336-2ab08e6c553so2429575ad.3\n for ;\n Sat, 18 Apr 2026 10:30:36 -0700 (PDT)","from ser8.. 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The decrement normally\nhappens in ksmbd_tcp_disconnect() at the end of the connection's\nlifetime.\n\nIf alloc_transport() fails in ksmbd_tcp_new_connection(), the function\nreleases the socket and returns -ENOMEM without going through\nksmbd_tcp_disconnect(), so active_num_conn never gets decremented.\nUnder memory pressure, repeated failures monotonically inflate the\ncounter until max_connections is reached and new clients are refused\nindefinitely.\n\nDecrement active_num_conn on this error path, matching the accounting\nrule used by ksmbd_kthread_fn() and ksmbd_tcp_disconnect().\n\nCommit 77ffbcac4e56 (\"smb: server: fix leak of active_num_conn in\nksmbd_tcp_new_connection()\") fixed the sibling leak on the kthread_run()\nfailure path; this patch closes the remaining one.\n\nReproduced with a debug build that adds a temporary module parameter\nguarding an early return at the top of alloc_transport(), forcing\nthe first N accept-time transport allocations to fail:\n\n * Configure ksmbd with \"max connections = 3\".\n * Force 5 successive alloc_transport() failures at the accept path.\n * Without the fix: active_num_conn drifts up to max_connections and\n subsequent legitimate mount.cifs attempts are refused with\n \"ksmbd: Limit the maximum number of connections(3)\" in dmesg.\n * With the fix: the counter is correctly decremented on each\n failure and legitimate mounts continue to succeed.\n\nTested by injecting 5 alloc_transport() failures with\nmax_connections=3 and verifying that subsequent mount.cifs attempts\nstill succeed on the patched kernel while the unpatched kernel\nrefuses them.\n\nFixes: 0d0d4680db22 (\"ksmbd: add max connections parameter\")\nCc: stable@vger.kernel.org\nSigned-off-by: DaeMyung Kang \n---\n fs/smb/server/transport_tcp.c | 2 ++\n 1 file changed, 2 insertions(+)","diff":"diff --git a/fs/smb/server/transport_tcp.c b/fs/smb/server/transport_tcp.c\nindex 7e29b06820e2..400412444838 100644\n--- a/fs/smb/server/transport_tcp.c\n+++ b/fs/smb/server/transport_tcp.c\n@@ -182,6 +182,8 @@ static int ksmbd_tcp_new_connection(struct socket *client_sk)\n \n \tt = alloc_transport(client_sk);\n \tif (!t) {\n+\t\tif (server_conf.max_connections)\n+\t\t\tatomic_dec(&active_num_conn);\n \t\tsock_release(client_sk);\n \t\treturn -ENOMEM;\n \t}\n","prefixes":["1/2"]}