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=-16.0 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, UNWANTED_LANGUAGE_BODY,URIBL_BLOCKED,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 1B025C43381 for ; Thu, 25 Feb 2021 23:45:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CF80664F37 for ; Thu, 25 Feb 2021 23:45:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232903AbhBYXop (ORCPT ); Thu, 25 Feb 2021 18:44:45 -0500 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:59242 "EHLO mx0b-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232674AbhBYXo0 (ORCPT ); Thu, 25 Feb 2021 18:44:26 -0500 Received: from pps.filterd (m0109331.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 11PNhhOP014138 for ; Thu, 25 Feb 2021 15:43:45 -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=E0ULp9pT+e++iTwzoI3j7hl8M6GoQAkpZEJr2rX/hkE=; b=Y5w8RnwLPX8ObStJkk9f9SHii+8RVMgFZ0O/xSG1CQm5Oc7SqXc8wJ3SBd+xyQ7GUumx db/9a/v78MBox9eY8OnAxsYT+A0Yk+dH0BL/X7OVZ/breThu2Vzj9LGVa2UCukFvObBP /Lmins/prxdIqGtIG6O+EqUy31JTT2/3PxY= Received: from mail.thefacebook.com ([163.114.132.120]) by mx0a-00082601.pphosted.com with ESMTP id 36x96bvgu1-6 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Thu, 25 Feb 2021 15:43:44 -0800 Received: from intmgw001.37.frc1.facebook.com (2620:10d:c085:108::8) by mail.thefacebook.com (2620:10d:c085:21d::6) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1979.3; Thu, 25 Feb 2021 15:43:43 -0800 Received: by devbig006.ftw2.facebook.com (Postfix, from userid 4523) id 2AEB662E1BF5; Thu, 25 Feb 2021 15:43:39 -0800 (PST) From: Song Liu To: , , CC: , , , , Song Liu Subject: [PATCH v6 bpf-next 2/6] bpf: prevent deadlock from recursive bpf_task_storage_[get|delete] Date: Thu, 25 Feb 2021 15:43:15 -0800 Message-ID: <20210225234319.336131-3-songliubraving@fb.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20210225234319.336131-1-songliubraving@fb.com> References: <20210225234319.336131-1-songliubraving@fb.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-FB-Internal: Safe Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.369,18.0.761 definitions=2021-02-25_15:2021-02-24,2021-02-25 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 spamscore=0 lowpriorityscore=0 suspectscore=0 bulkscore=0 phishscore=0 mlxscore=0 adultscore=0 malwarescore=0 impostorscore=0 priorityscore=1501 mlxlogscore=743 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2102250180 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org 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. 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 --- include/linux/bpf_local_storage.h | 3 +- kernel/bpf/bpf_inode_storage.c | 2 +- kernel/bpf/bpf_local_storage.c | 11 +++++- kernel/bpf/bpf_task_storage.c | 59 ++++++++++++++++++++++++++----- net/core/bpf_sk_storage.c | 2 +- 5 files changed, 65 insertions(+), 12 deletions(-) diff --git a/include/linux/bpf_local_storage.h b/include/linux/bpf_local_= storage.h index b2c9463f36a1b..b902c580c48d5 100644 --- a/include/linux/bpf_local_storage.h +++ b/include/linux/bpf_local_storage.h @@ -126,7 +126,8 @@ bpf_local_storage_lookup(struct bpf_local_storage *lo= cal_storage, struct bpf_local_storage_map *smap, bool cacheit_lockit); =20 -void bpf_local_storage_map_free(struct bpf_local_storage_map *smap); +void bpf_local_storage_map_free(struct bpf_local_storage_map *smap, + int __percpu *busy_counter); =20 int bpf_local_storage_map_check_btf(const struct bpf_map *map, const struct btf *btf, diff --git a/kernel/bpf/bpf_inode_storage.c b/kernel/bpf/bpf_inode_storag= e.c index 6639640523c0b..da753721457cb 100644 --- a/kernel/bpf/bpf_inode_storage.c +++ b/kernel/bpf/bpf_inode_storage.c @@ -237,7 +237,7 @@ static void inode_storage_map_free(struct bpf_map *ma= p) =20 smap =3D (struct bpf_local_storage_map *)map; bpf_local_storage_cache_idx_free(&inode_cache, smap->cache_idx); - bpf_local_storage_map_free(smap); + bpf_local_storage_map_free(smap, NULL); } =20 static int inode_storage_map_btf_id; diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storag= e.c index 9bd47ad2b26f1..b305270b7a4bd 100644 --- a/kernel/bpf/bpf_local_storage.c +++ b/kernel/bpf/bpf_local_storage.c @@ -474,7 +474,8 @@ void bpf_local_storage_cache_idx_free(struct bpf_loca= l_storage_cache *cache, spin_unlock(&cache->idx_lock); } =20 -void bpf_local_storage_map_free(struct bpf_local_storage_map *smap) +void bpf_local_storage_map_free(struct bpf_local_storage_map *smap, + int __percpu *busy_counter) { struct bpf_local_storage_elem *selem; struct bpf_local_storage_map_bucket *b; @@ -503,7 +504,15 @@ void bpf_local_storage_map_free(struct bpf_local_sto= rage_map *smap) while ((selem =3D hlist_entry_safe( rcu_dereference_raw(hlist_first_rcu(&b->list)), struct bpf_local_storage_elem, map_node))) { + if (busy_counter) { + migrate_disable(); + __this_cpu_inc(*busy_counter); + } bpf_selem_unlink(selem); + if (busy_counter) { + __this_cpu_dec(*busy_counter); + migrate_enable(); + } cond_resched_rcu(); } rcu_read_unlock(); diff --git a/kernel/bpf/bpf_task_storage.c b/kernel/bpf/bpf_task_storage.= c index baf3566e23233..fd3c74ef608ef 100644 --- a/kernel/bpf/bpf_task_storage.c +++ b/kernel/bpf/bpf_task_storage.c @@ -20,6 +20,31 @@ =20 DEFINE_BPF_STORAGE_CACHE(task_cache); =20 +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) !=3D 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 =3D 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(); =20 /* 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; } =20 + bpf_task_storage_lock(); sdata =3D 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 b= pf_map *map, void *key, goto out; } =20 + bpf_task_storage_lock(); sdata =3D bpf_local_storage_update( task, (struct bpf_local_storage_map *)map, value, map_flags); + bpf_task_storage_unlock(); =20 err =3D PTR_ERR_OR_ZERO(sdata); out: @@ -185,7 +216,9 @@ static int bpf_pid_task_storage_delete_elem(struct bp= f_map *map, void *key) goto out; } =20 + bpf_task_storage_lock(); err =3D task_storage_delete(task, map); + bpf_task_storage_unlock(); out: put_pid(pid); return err; @@ -202,34 +235,44 @@ BPF_CALL_4(bpf_task_storage_get, struct bpf_map *, = map, struct task_struct *, if (!task) return (unsigned long)NULL; =20 + if (!bpf_task_storage_trylock()) + return (unsigned long)NULL; + sdata =3D task_storage_lookup(task, map, true); if (sdata) - return (unsigned long)sdata->data; + goto unlock; =20 /* 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 =3D 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; - } =20 - return (unsigned long)NULL; +unlock: + bpf_task_storage_unlock(); + return IS_ERR_OR_NULL(sdata) ? (unsigned long)NULL : + (unsigned long)sdata->data; } =20 BPF_CALL_2(bpf_task_storage_delete, struct bpf_map *, map, struct task_s= truct *, task) { + int ret; + if (!task) return -EINVAL; =20 + if (!bpf_task_storage_trylock()) + return -EBUSY; + /* This helper must only be called from places where the lifetime of th= e 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 =3D task_storage_delete(task, map); + bpf_task_storage_unlock(); + return ret; } =20 static int notsupp_get_next_key(struct bpf_map *map, void *key, void *ne= xt_key) @@ -255,7 +298,7 @@ static void task_storage_map_free(struct bpf_map *map= ) =20 smap =3D (struct bpf_local_storage_map *)map; bpf_local_storage_cache_idx_free(&task_cache, smap->cache_idx); - bpf_local_storage_map_free(smap); + bpf_local_storage_map_free(smap, &bpf_task_storage_busy); } =20 static int task_storage_map_btf_id; diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c index 4edd033e899c0..cc3712ad8716f 100644 --- a/net/core/bpf_sk_storage.c +++ b/net/core/bpf_sk_storage.c @@ -89,7 +89,7 @@ static void bpf_sk_storage_map_free(struct bpf_map *map= ) =20 smap =3D (struct bpf_local_storage_map *)map; bpf_local_storage_cache_idx_free(&sk_cache, smap->cache_idx); - bpf_local_storage_map_free(smap); + bpf_local_storage_map_free(smap, NULL); } =20 static struct bpf_map *bpf_sk_storage_map_alloc(union bpf_attr *attr) --=20 2.24.1