From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AE729C48BD5 for ; Tue, 25 Jun 2019 21:39:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 82C8E2084B for ; Tue, 25 Jun 2019 21:39:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=fb.com header.i=@fb.com header.b="qmaiAvFn" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726379AbfFYVjF (ORCPT ); Tue, 25 Jun 2019 17:39:05 -0400 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:7742 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726014AbfFYVjE (ORCPT ); Tue, 25 Jun 2019 17:39:04 -0400 Received: from pps.filterd (m0044012.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x5PLYk3M012533 for ; Tue, 25 Jun 2019 14:39:03 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : mime-version : content-type; s=facebook; bh=6Qb5WBexFT5B6u9rozg9q9FpGOZk1JNFFnUiYC37ZO0=; b=qmaiAvFnuImuVeLjJgMx1v57y1gAXNz7RDZZ85he53r+OlswPeTARhWR/O9bGEvUFM8/ 7Jr0yXkTIJW/qkU5i3azXL40mWDYvvJwg8ROkmGrdygCrHjR3OzRFc565lKtgopK+Nhd MtsB3QnnDIminohubmbHpBZ04KQqgmoI07g= Received: from maileast.thefacebook.com ([163.114.130.16]) by mx0a-00082601.pphosted.com with ESMTP id 2tbnnb1k4d-3 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Tue, 25 Jun 2019 14:39:03 -0700 Received: from mx-out.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:83::4) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1713.5; Tue, 25 Jun 2019 14:39:01 -0700 Received: by devvm2643.prn2.facebook.com (Postfix, from userid 111017) id D752013B668B9; Tue, 25 Jun 2019 14:38:59 -0700 (PDT) Smtp-Origin-Hostprefix: devvm From: Roman Gushchin Smtp-Origin-Hostname: devvm2643.prn2.facebook.com To: Alexei Starovoitov , Tejun Heo , CC: Daniel Borkmann , , , Roman Gushchin Smtp-Origin-Cluster: prn2c23 Subject: [PATCH v2 bpf-next] bpf: fix cgroup bpf release synchronization Date: Tue, 25 Jun 2019 14:38:58 -0700 Message-ID: <20190625213858.22459-1-guro@fb.com> X-Mailer: git-send-email 2.17.1 X-FB-Internal: Safe MIME-Version: 1.0 Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-06-25_14:,, signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 priorityscore=1501 malwarescore=0 suspectscore=2 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=709 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906250167 X-FB-Internal: deliver Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Since commit 4bfc0bb2c60e ("bpf: decouple the lifetime of cgroup_bpf from cgroup itself"), cgroup_bpf release occurs asynchronously (from a worker context), and before the release of the cgroup itself. This introduced a previously non-existing race between the release and update paths. E.g. if a leaf's cgroup_bpf is released and a new bpf program is attached to the one of ancestor cgroups at the same time. The race may result in double-free and other memory corruptions. To fix the problem, let's protect the body of cgroup_bpf_release() with cgroup_mutex, as it was effectively previously, when all this code was called from the cgroup release path with cgroup mutex held. Also let's skip cgroups, which have no chances to invoke a bpf program, on the update path. If the cgroup bpf refcnt reached 0, it means that the cgroup is offline (no attached processes), and there are no associated sockets left. It means there is no point in updating effective progs array! And it can lead to a leak, if it happens after the release. So, let's skip such cgroups. Big thanks for Tejun Heo for discovering and debugging of this problem! Fixes: 4bfc0bb2c60e ("bpf: decouple the lifetime of cgroup_bpf from cgroup itself") Reported-by: Tejun Heo Signed-off-by: Roman Gushchin --- kernel/bpf/cgroup.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c index c225c42e114a..077ed3a19848 100644 --- a/kernel/bpf/cgroup.c +++ b/kernel/bpf/cgroup.c @@ -16,6 +16,8 @@ #include #include +#include "../cgroup/cgroup-internal.h" + DEFINE_STATIC_KEY_FALSE(cgroup_bpf_enabled_key); EXPORT_SYMBOL(cgroup_bpf_enabled_key); @@ -38,6 +40,8 @@ static void cgroup_bpf_release(struct work_struct *work) struct bpf_prog_array *old_array; unsigned int type; + mutex_lock(&cgroup_mutex); + for (type = 0; type < ARRAY_SIZE(cgrp->bpf.progs); type++) { struct list_head *progs = &cgrp->bpf.progs[type]; struct bpf_prog_list *pl, *tmp; @@ -54,10 +58,12 @@ static void cgroup_bpf_release(struct work_struct *work) } old_array = rcu_dereference_protected( cgrp->bpf.effective[type], - percpu_ref_is_dying(&cgrp->bpf.refcnt)); + lockdep_is_held(&cgroup_mutex)); bpf_prog_array_free(old_array); } + mutex_unlock(&cgroup_mutex); + percpu_ref_exit(&cgrp->bpf.refcnt); cgroup_put(cgrp); } @@ -229,6 +235,9 @@ static int update_effective_progs(struct cgroup *cgrp, css_for_each_descendant_pre(css, &cgrp->self) { struct cgroup *desc = container_of(css, struct cgroup, self); + if (percpu_ref_is_zero(&desc->bpf.refcnt)) + continue; + err = compute_effective_progs(desc, type, &desc->bpf.inactive); if (err) goto cleanup; @@ -238,6 +247,14 @@ static int update_effective_progs(struct cgroup *cgrp, css_for_each_descendant_pre(css, &cgrp->self) { struct cgroup *desc = container_of(css, struct cgroup, self); + if (percpu_ref_is_zero(&desc->bpf.refcnt)) { + if (unlikely(desc->bpf.inactive)) { + bpf_prog_array_free(desc->bpf.inactive); + desc->bpf.inactive = NULL; + } + continue; + } + activate_effective_progs(desc, type, desc->bpf.inactive); desc->bpf.inactive = NULL; } -- 2.21.0