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[85.204.121.218]) by smtp.gmail.com with ESMTPSA id d4sm1213174lfi.32.2019.11.21.03.36.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 Nov 2019 03:36:19 -0800 (PST) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id 0D9681818B9; Thu, 21 Nov 2019 12:36:19 +0100 (CET) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= To: Tetsuo Handa Cc: Alexei Starovoitov , Jesper Dangaard Brouer , Alexei Starovoitov , Daniel Borkmann , syzbot , ddstreet@ieee.org, Dmitry Vyukov , LKML , Network Development , syzkaller-bugs , bpf , Yonghong Song Subject: Re: unregister_netdevice: waiting for DEV to become free (2) In-Reply-To: <6f69f704-b51d-c3cb-02c6-8e6eb93f4194@i-love.sakura.ne.jp> References: <00000000000056268e05737dcb95@google.com> <0000000000007d22100573d66078@google.com> <063a57ba-7723-6513-043e-ee99c5797271@I-love.SAKURA.ne.jp> <87imopgere.fsf@toke.dk> <6f69f704-b51d-c3cb-02c6-8e6eb93f4194@i-love.sakura.ne.jp> X-Clacks-Overhead: GNU Terry Pratchett Date: Thu, 21 Nov 2019 12:36:18 +0100 Message-ID: <87r2217971.fsf@toke.dk> MIME-Version: 1.0 X-MC-Unique: sG2OA2RIMWOdKffZa8RKmg-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Tetsuo Handa writes: > Hello. > > syzbot is still reporting that bpf(BPF_MAP_UPDATE_ELEM) causes > unregister_netdevice() to hang. It seems that commit 546ac1ffb70d25b5 > ("bpf: add devmap, a map for storing net device references") assigned > dtab->netdev_map[i] at dev_map_update_elem() but commit 6f9d451ab1a33728 > ("xdp: Add devmap_hash map type for looking up devices by hashed index") > forgot to assign dtab->netdev_map[idx] at __dev_map_hash_update_elem() > when dev is newly allocated by __dev_map_alloc_node(). As far as I and > syzbot tested, https://syzkaller.appspot.com/x/patch.diff?x=3D140dd206e00= 000 > can avoid the problem, but I don't know whether this is right location to > assign it. Please check and fix. Hi Tetsuo Sorry for missing this email last week :( I think the issue is not a missing update of dtab->netdev_map (that is not used at all for DEVMAP_HASH), but rather that dev_map_free() is not cleaning up properly for DEVMAP_HASH types. Could you please check if the patch below helps? -Toke diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c index 3867864cdc2f..42ccfcb38424 100644 --- a/kernel/bpf/devmap.c +++ b/kernel/bpf/devmap.c @@ -74,7 +74,7 @@ struct bpf_dtab_netdev { =20 struct bpf_dtab { =09struct bpf_map map; -=09struct bpf_dtab_netdev **netdev_map; +=09struct bpf_dtab_netdev **netdev_map; /* DEVMAP type only */ =09struct list_head __percpu *flush_list; =09struct list_head list; =20 @@ -101,6 +101,12 @@ static struct hlist_head *dev_map_create_hash(unsigned= int entries) =09return hash; } =20 +static inline struct hlist_head *dev_map_index_hash(struct bpf_dtab *dtab, +=09=09=09=09=09=09 int idx) +{ +=09return &dtab->dev_index_head[idx & (dtab->n_buckets - 1)]; +} + static int dev_map_init_map(struct bpf_dtab *dtab, union bpf_attr *attr) { =09int err, cpu; @@ -143,24 +149,22 @@ static int dev_map_init_map(struct bpf_dtab *dtab, un= ion bpf_attr *attr) =09for_each_possible_cpu(cpu) =09=09INIT_LIST_HEAD(per_cpu_ptr(dtab->flush_list, cpu)); =20 -=09dtab->netdev_map =3D bpf_map_area_alloc(dtab->map.max_entries * -=09=09=09=09=09 sizeof(struct bpf_dtab_netdev *), -=09=09=09=09=09 dtab->map.numa_node); -=09if (!dtab->netdev_map) -=09=09goto free_percpu; - =09if (attr->map_type =3D=3D BPF_MAP_TYPE_DEVMAP_HASH) { =09=09dtab->dev_index_head =3D dev_map_create_hash(dtab->n_buckets); =09=09if (!dtab->dev_index_head) -=09=09=09goto free_map_area; +=09=09=09goto free_percpu; =20 =09=09spin_lock_init(&dtab->index_lock); +=09} else { +=09=09dtab->netdev_map =3D bpf_map_area_alloc(dtab->map.max_entries * +=09=09=09=09=09=09 sizeof(struct bpf_dtab_netdev *), +=09=09=09=09=09=09 dtab->map.numa_node); +=09=09if (!dtab->netdev_map) +=09=09=09goto free_percpu; =09} =20 =09return 0; =20 -free_map_area: -=09bpf_map_area_free(dtab->netdev_map); free_percpu: =09free_percpu(dtab->flush_list); free_charge: @@ -228,21 +232,40 @@ static void dev_map_free(struct bpf_map *map) =09=09=09cond_resched(); =09} =20 -=09for (i =3D 0; i < dtab->map.max_entries; i++) { -=09=09struct bpf_dtab_netdev *dev; +=09if (dtab->map.map_type =3D=3D BPF_MAP_TYPE_DEVMAP_HASH) { +=09=09for (i =3D 0; i < dtab->n_buckets; i++) { +=09=09=09struct bpf_dtab_netdev *dev; +=09=09=09struct hlist_head *head; +=09=09=09struct hlist_node *next; =20 -=09=09dev =3D dtab->netdev_map[i]; -=09=09if (!dev) -=09=09=09continue; +=09=09=09head =3D dev_map_index_hash(dtab, i); =20 -=09=09free_percpu(dev->bulkq); -=09=09dev_put(dev->dev); -=09=09kfree(dev); +=09=09=09hlist_for_each_entry_safe(dev, next, head, index_hlist) { +=09=09=09=09hlist_del_rcu(&dev->index_hlist); +=09=09=09=09free_percpu(dev->bulkq); +=09=09=09=09dev_put(dev->dev); +=09=09=09=09kfree(dev); +=09=09=09} +=09=09} + +=09=09kfree(dtab->dev_index_head); +=09} else { +=09=09for (i =3D 0; i < dtab->map.max_entries; i++) { +=09=09=09struct bpf_dtab_netdev *dev; + +=09=09=09dev =3D dtab->netdev_map[i]; +=09=09=09if (!dev) +=09=09=09=09continue; + +=09=09=09free_percpu(dev->bulkq); +=09=09=09dev_put(dev->dev); +=09=09=09kfree(dev); +=09=09} + +=09=09bpf_map_area_free(dtab->netdev_map); =09} =20 =09free_percpu(dtab->flush_list); -=09bpf_map_area_free(dtab->netdev_map); -=09kfree(dtab->dev_index_head); =09kfree(dtab); } =20 @@ -263,12 +286,6 @@ static int dev_map_get_next_key(struct bpf_map *map, v= oid *key, void *next_key) =09return 0; } =20 -static inline struct hlist_head *dev_map_index_hash(struct bpf_dtab *dtab, -=09=09=09=09=09=09 int idx) -{ -=09return &dtab->dev_index_head[idx & (dtab->n_buckets - 1)]; -} - struct bpf_dtab_netdev *__dev_map_hash_lookup_elem(struct bpf_map *map, u3= 2 key) { =09struct bpf_dtab *dtab =3D container_of(map, struct bpf_dtab, map);