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Date: Mon, 12 Aug 2019 12:17:16 +0200 From: Daniel Borkmann <daniel@...earbox.net> To: Stanislav Fomichev <sdf@...gle.com>, netdev@...r.kernel.org, bpf@...r.kernel.org Cc: davem@...emloft.net, ast@...nel.org, Martin KaFai Lau <kafai@...com>, Yonghong Song <yhs@...com> Subject: Re: [PATCH bpf-next v2 2/4] bpf: support cloning sk storage on accept() On 8/9/19 6:10 PM, Stanislav Fomichev wrote: > Add new helper bpf_sk_storage_clone which optionally clones sk storage > and call it from sk_clone_lock. > > Cc: Martin KaFai Lau <kafai@...com> > Cc: Yonghong Song <yhs@...com> > Signed-off-by: Stanislav Fomichev <sdf@...gle.com> [...] > +int bpf_sk_storage_clone(const struct sock *sk, struct sock *newsk) > +{ > + struct bpf_sk_storage *new_sk_storage = NULL; > + struct bpf_sk_storage *sk_storage; > + struct bpf_sk_storage_elem *selem; > + int ret; > + > + RCU_INIT_POINTER(newsk->sk_bpf_storage, NULL); > + > + rcu_read_lock(); > + sk_storage = rcu_dereference(sk->sk_bpf_storage); > + > + if (!sk_storage || hlist_empty(&sk_storage->list)) > + goto out; > + > + hlist_for_each_entry_rcu(selem, &sk_storage->list, snode) { > + struct bpf_sk_storage_elem *copy_selem; > + struct bpf_sk_storage_map *smap; > + struct bpf_map *map; > + int refold; > + > + smap = rcu_dereference(SDATA(selem)->smap); > + if (!(smap->map.map_flags & BPF_F_CLONE)) > + continue; > + > + map = bpf_map_inc_not_zero(&smap->map, false); > + if (IS_ERR(map)) > + continue; > + > + copy_selem = bpf_sk_storage_clone_elem(newsk, smap, selem); > + if (!copy_selem) { > + ret = -ENOMEM; > + bpf_map_put(map); > + goto err; > + } > + > + if (new_sk_storage) { > + selem_link_map(smap, copy_selem); > + __selem_link_sk(new_sk_storage, copy_selem); > + } else { > + ret = sk_storage_alloc(newsk, smap, copy_selem); > + if (ret) { > + kfree(copy_selem); > + atomic_sub(smap->elem_size, > + &newsk->sk_omem_alloc); > + bpf_map_put(map); > + goto err; > + } > + > + new_sk_storage = rcu_dereference(copy_selem->sk_storage); > + } > + bpf_map_put(map); The map get/put combination /under/ RCU read lock seems a bit odd to me, could you exactly describe the race that this would be preventing? > + } > + > +out: > + rcu_read_unlock(); > + return 0; > + > +err: > + rcu_read_unlock(); > + > + bpf_sk_storage_free(newsk); > + return ret; > +} Thanks, Daniel
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