From patchwork Tue Feb 23 01:20:10 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Song Liu X-Patchwork-Id: 12099705 X-Patchwork-Delegate: bpf@iogearbox.net 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=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 68454C433DB for ; Tue, 23 Feb 2021 01:22:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 22C846023B for ; Tue, 23 Feb 2021 01:22:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230367AbhBWBWD (ORCPT ); Mon, 22 Feb 2021 20:22:03 -0500 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:5042 "EHLO mx0b-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230326AbhBWBWA (ORCPT ); Mon, 22 Feb 2021 20:22:00 -0500 Received: from pps.filterd (m0148460.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 11N13elt023062 for ; Mon, 22 Feb 2021 17:21:19 -0800 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : content-type; s=facebook; bh=pFqtEeOH6Z/cu2ZEQtuYa86l0748EAYF++/eLsRvjAM=; b=F+cLt1RRabZe3kgTlOJdQ1IpNlUDD2s5K3mOTONvCas/ratgT9hesKXBgBCQmAlD4BbQ abFJz8VHiWd9hcXnrSvh5fHXQzyIfF/wdWmh/TORY8/ePMAI/Ir/AS8GcTP0Ogn4824G k9o6tGMsSa46Wp3eNPeu+z8ExMVNl9TxyFo= Received: from mail.thefacebook.com ([163.114.132.120]) by mx0a-00082601.pphosted.com with ESMTP id 36u0tubfun-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Mon, 22 Feb 2021 17:21:19 -0800 Received: from intmgw006.03.ash8.facebook.com (2620:10d:c085:108::8) by mail.thefacebook.com (2620:10d:c085:11d::5) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1979.3; Mon, 22 Feb 2021 17:21:17 -0800 Received: by devbig006.ftw2.facebook.com (Postfix, from userid 4523) id 96BB862E0887; Mon, 22 Feb 2021 17:21:12 -0800 (PST) From: Song Liu To: , , CC: , , , , Song Liu Subject: [PATCH v4 bpf-next 2/6] bpf: prevent deadlock from recursive bpf_task_storage_[get|delete] Date: Mon, 22 Feb 2021 17:20:10 -0800 Message-ID: <20210223012014.2087583-3-songliubraving@fb.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20210223012014.2087583-1-songliubraving@fb.com> References: <20210223012014.2087583-1-songliubraving@fb.com> MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.369,18.0.761 definitions=2021-02-22_08:2021-02-22,2021-02-22 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 impostorscore=0 malwarescore=0 suspectscore=0 adultscore=0 spamscore=0 phishscore=0 lowpriorityscore=0 mlxlogscore=726 clxscore=1015 mlxscore=0 bulkscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2102230006 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net BPF helpers bpf_task_storage_[get|delete] could hold two locks: bpf_local_storage_map_bucket->lock and bpf_local_storage->lock. Calling these helpers from fentry/fexit programs on functions in bpf_*_storage.c may cause deadlock on either locks. Prevent such deadlock with a per cpu counter, bpf_task_storage_busy, which is similar to bpf_prog_active. We need this counter to be global, because the two locks here belong to two different objects: bpf_local_storage_map and bpf_local_storage. If we pick one of them as the owner of the counter, it is still possible to trigger deadlock on the other lock. For example, if bpf_local_storage_map owns the counters, it cannot prevent deadlock on bpf_local_storage->lock when two maps are used. Signed-off-by: Song Liu --- kernel/bpf/bpf_task_storage.c | 57 ++++++++++++++++++++++++++++++----- 1 file changed, 50 insertions(+), 7 deletions(-) diff --git a/kernel/bpf/bpf_task_storage.c b/kernel/bpf/bpf_task_storage.c index 2034019966d44..ed7d2e02b1c19 100644 --- a/kernel/bpf/bpf_task_storage.c +++ b/kernel/bpf/bpf_task_storage.c @@ -20,6 +20,31 @@ DEFINE_BPF_STORAGE_CACHE(task_cache); +DEFINE_PER_CPU(int, bpf_task_storage_busy); + +static void bpf_task_storage_lock(void) +{ + migrate_disable(); + __this_cpu_inc(bpf_task_storage_busy); +} + +static void bpf_task_storage_unlock(void) +{ + __this_cpu_dec(bpf_task_storage_busy); + migrate_enable(); +} + +static bool bpf_task_storage_trylock(void) +{ + migrate_disable(); + if (unlikely(__this_cpu_inc_return(bpf_task_storage_busy) != 1)) { + __this_cpu_dec(bpf_task_storage_busy); + migrate_enable(); + return false; + } + return true; +} + static struct bpf_local_storage __rcu **task_storage_ptr(void *owner) { struct task_struct *task = owner; @@ -67,6 +92,7 @@ void bpf_task_storage_free(struct task_struct *task) * when unlinking elem from the local_storage->list and * the map's bucket->list. */ + bpf_task_storage_lock(); raw_spin_lock_irqsave(&local_storage->lock, flags); hlist_for_each_entry_safe(selem, n, &local_storage->list, snode) { /* Always unlink from map before unlinking from @@ -77,6 +103,7 @@ void bpf_task_storage_free(struct task_struct *task) local_storage, selem, false); } raw_spin_unlock_irqrestore(&local_storage->lock, flags); + bpf_task_storage_unlock(); rcu_read_unlock(); /* free_task_storage should always be true as long as @@ -109,7 +136,9 @@ static void *bpf_pid_task_storage_lookup_elem(struct bpf_map *map, void *key) goto out; } + bpf_task_storage_lock(); sdata = task_storage_lookup(task, map, true); + bpf_task_storage_unlock(); put_pid(pid); return sdata ? sdata->data : NULL; out: @@ -141,8 +170,10 @@ static int bpf_pid_task_storage_update_elem(struct bpf_map *map, void *key, goto out; } + bpf_task_storage_lock(); sdata = bpf_local_storage_update( task, (struct bpf_local_storage_map *)map, value, map_flags); + bpf_task_storage_unlock(); err = PTR_ERR_OR_ZERO(sdata); out: @@ -185,7 +216,9 @@ static int bpf_pid_task_storage_delete_elem(struct bpf_map *map, void *key) goto out; } + bpf_task_storage_lock(); err = task_storage_delete(task, map); + bpf_task_storage_unlock(); out: put_pid(pid); return err; @@ -207,34 +240,44 @@ BPF_CALL_4(bpf_task_storage_get, struct bpf_map *, map, struct task_struct *, if (!task || !task_storage_ptr(task)) return (unsigned long)NULL; + if (!bpf_task_storage_trylock()) + return (unsigned long)NULL; + sdata = task_storage_lookup(task, map, true); if (sdata) - return (unsigned long)sdata->data; + goto unlock; /* only allocate new storage, when the task is refcounted */ if (refcount_read(&task->usage) && - (flags & BPF_LOCAL_STORAGE_GET_F_CREATE)) { + (flags & BPF_LOCAL_STORAGE_GET_F_CREATE)) sdata = bpf_local_storage_update( task, (struct bpf_local_storage_map *)map, value, BPF_NOEXIST); - return IS_ERR(sdata) ? (unsigned long)NULL : - (unsigned long)sdata->data; - } - return (unsigned long)NULL; +unlock: + bpf_task_storage_unlock(); + return IS_ERR_OR_NULL(sdata) ? (unsigned long)NULL : + (unsigned long)sdata->data; } BPF_CALL_2(bpf_task_storage_delete, struct bpf_map *, map, struct task_struct *, task) { + int ret; + if (!task) return -EINVAL; + if (!bpf_task_storage_trylock()) + return -EBUSY; + /* This helper must only be called from places where the lifetime of the task * is guaranteed. Either by being refcounted or by being protected * by an RCU read-side critical section. */ - return task_storage_delete(task, map); + ret = task_storage_delete(task, map); + bpf_task_storage_unlock(); + return ret; } static int notsupp_get_next_key(struct bpf_map *map, void *key, void *next_key)