[{"id":3679800,"web_url":"http://patchwork.ozlabs.org/comment/3679800/","msgid":"<42f9cfbf-8189-2bba-0541-acf7a3536968@ssi.bg>","list_archive_url":null,"date":"2026-04-21T10:35:34","subject":"Re: [PATCH net] ipvs: fix races around est_mutex and est_cpulist","submitter":{"id":2825,"url":"http://patchwork.ozlabs.org/api/people/2825/","name":"Julian Anastasov","email":"ja@ssi.bg"},"content":"Hello,\n\nOn Mon, 20 Apr 2026, Julian Anastasov wrote:\n\n> Sashiko reports for races and possible crash around\n> the usage of est_cpulist_valid and sysctl_est_cpulist.\n> The problem is that we do not lock est_mutex in some\n> places which can lead to wrong write ordering and\n> as result problems when calling cpumask_weight()\n> and cpumask_empty().\n> \n> Fix them by moving the est_max_threads read/write under\n> locked est_mutex. Do the same for one ip_vs_est_reload_start()\n> call to protect the cpumask_empty() usage of sysctl_est_cpulist.\n> \n> Link: https://sashiko.dev/#/patchset/20260331165015.2777765-1-longman%40redhat.com\n> Fixes: f0be83d54217 (\"ipvs: add est_cpulist and est_nice sysctl vars\")\n> Signed-off-by: Julian Anastasov \n\n\tAccording to Sashiko, this patch needs more\nwork, I'll send new version when I'm ready...\n\npw-bot: changes-requested\n\n\n> ---\n> \n> Note that this patch complements v2 of patchset from 31-MAR-26\n> \"ipvs: Fix incorrect use of HK_TYPE_KTHREAD housekeeping cpumask\"\n> and can be applied before it to avoid the bad AI reviews:\n> \n> https://lore.kernel.org/all/20260331165015.2777765-1-longman@redhat.com/\n> \n> net/netfilter/ipvs/ip_vs_ctl.c | 5 +++++\n> net/netfilter/ipvs/ip_vs_est.c | 22 +++++++++++++++-------\n> 2 files changed, 20 insertions(+), 7 deletions(-)\n> \n> diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c\n> index caec516856e9..8778e174ef56 100644\n> --- a/net/netfilter/ipvs/ip_vs_ctl.c\n> +++ b/net/netfilter/ipvs/ip_vs_ctl.c\n> @@ -1812,11 +1812,16 @@ ip_vs_add_service(struct netns_ipvs *ipvs, struct ip_vs_service_user_kern *u,\n> \t*svc_p = svc;\n> \n> \tif (!READ_ONCE(ipvs->enable)) {\n> +\t\tmutex_lock(&ipvs->est_mutex);\n> +\n> \t\t/* Now there is a service - full throttle */\n> \t\tWRITE_ONCE(ipvs->enable, 1);\n> \n> +\t\tipvs->est_max_threads = ip_vs_est_max_threads(ipvs);\n> +\n> \t\t/* Start estimation for first time */\n> \t\tip_vs_est_reload_start(ipvs);\n> +\t\tmutex_unlock(&ipvs->est_mutex);\n> \t}\n> \n> \treturn 0;\n> diff --git a/net/netfilter/ipvs/ip_vs_est.c b/net/netfilter/ipvs/ip_vs_est.c\n> index 433ba3cab58c..6c9981d5611e 100644\n> --- a/net/netfilter/ipvs/ip_vs_est.c\n> +++ b/net/netfilter/ipvs/ip_vs_est.c\n> @@ -68,6 +68,10 @@\n> and the limit of estimators per kthread\n> - est_add_ktid: ktid where to add new ests, can point to empty slot where\n> we should add kt data\n> + - data protected by service_mutex: est_temp_list, est_add_ktid\n> + - data protected by est_mutex: est_kt_count, est_kt_arr, est_max_threads,\n> + sysctl_est_cpulist, est_cpulist_valid, sysctl_est_nice, est_stopped,\n> + sysctl_run_estimation\n> */\n> \n> static struct lock_class_key __ipvs_est_key;\n> @@ -229,6 +233,8 @@ static int ip_vs_estimation_kthread(void *data)\n> /* Schedule stop/start for kthread tasks */\n> void ip_vs_est_reload_start(struct netns_ipvs *ipvs)\n> {\n> +\tlockdep_assert_held(&ipvs->est_mutex);\n> +\n> \t/* Ignore reloads before first service is added */\n> \tif (!READ_ONCE(ipvs->enable))\n> \t\treturn;\n> @@ -304,12 +310,17 @@ static int ip_vs_est_add_kthread(struct netns_ipvs *ipvs)\n> \tvoid *arr = NULL;\n> \tint i;\n> \n> -\tif ((unsigned long)ipvs->est_kt_count >= ipvs->est_max_threads &&\n> -\t READ_ONCE(ipvs->enable) && ipvs->est_max_threads)\n> -\t\treturn -EINVAL;\n> -\n> \tmutex_lock(&ipvs->est_mutex);\n> \n> +\t/* Allow kt 0 data to be created before the services are added\n> +\t * and limit the kthreads when services are present.\n> +\t */\n> +\tif ((unsigned long)ipvs->est_kt_count >= ipvs->est_max_threads &&\n> +\t READ_ONCE(ipvs->enable) && ipvs->est_max_threads) {\n> +\t\tret = -EINVAL;\n> +\t\tgoto out;\n> +\t}\n> +\n> \tfor (i = 0; i < id; i++) {\n> \t\tif (!ipvs->est_kt_arr[i])\n> \t\t\tbreak;\n> @@ -485,9 +496,6 @@ int ip_vs_start_estimator(struct netns_ipvs *ipvs, struct ip_vs_stats *stats)\n> \tstruct ip_vs_estimator *est = &stats->est;\n> \tint ret;\n> \n> -\tif (!ipvs->est_max_threads && READ_ONCE(ipvs->enable))\n> -\t\tipvs->est_max_threads = ip_vs_est_max_threads(ipvs);\n> -\n> \test->ktid = -1;\n> \test->ktrow = IPVS_EST_NTICKS - 1;\t/* Initial delay */\n> \n> -- \n> 2.53.0\n\nRegards\n\n--\nJulian Anastasov ","headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","netfilter-devel@vger.kernel.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (4096-bit key;\n unprotected) header.d=ssi.bg header.i=@ssi.bg header.a=rsa-sha256\n header.s=ssi header.b=aWEtfu05;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n (client-ip=172.234.253.10; helo=sea.lore.kernel.org;\n envelope-from=netfilter-devel+bounces-12103-incoming=patchwork.ozlabs.org@vger.kernel.org;\n receiver=patchwork.ozlabs.org)","smtp.subspace.kernel.org;\n\tdkim=pass (4096-bit key) header.d=ssi.bg header.i=@ssi.bg header.b=\"aWEtfu05\"","smtp.subspace.kernel.org;\n arc=none smtp.client-ip=193.238.174.39","smtp.subspace.kernel.org;\n dmarc=pass (p=reject dis=none) header.from=ssi.bg","smtp.subspace.kernel.org;\n spf=pass smtp.mailfrom=ssi.bg"],"Received":["from sea.lore.kernel.org (sea.lore.kernel.org [172.234.253.10])\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 4g0JgV0RMPz1yCv\n\tfor ; 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