From: Stanislav Fomichev <sdf@google.com>
Date: Wed, 14 Aug 2019 10:37:49 -0700
Subject: bpf: support cloning sk storage on accept()
Patch-mainline: v5.4-rc1
Git-commit: 8f51dfc73bf181f2304e1498f55d5f452e060cbe
References: bsc#1154353
Add new helper bpf_sk_storage_clone which optionally clones sk storage
and call it from sk_clone_lock.
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Yonghong Song <yhs@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
include/net/bpf_sk_storage.h | 10 ++++
include/uapi/linux/bpf.h | 3 +
net/core/bpf_sk_storage.c | 104 +++++++++++++++++++++++++++++++++++++++++--
net/core/sock.c | 9 ++-
4 files changed, 120 insertions(+), 6 deletions(-)
--- a/include/net/bpf_sk_storage.h
+++ b/include/net/bpf_sk_storage.h
@@ -10,4 +10,14 @@ void bpf_sk_storage_free(struct sock *sk
extern const struct bpf_func_proto bpf_sk_storage_get_proto;
extern const struct bpf_func_proto bpf_sk_storage_delete_proto;
+#ifdef CONFIG_BPF_SYSCALL
+int bpf_sk_storage_clone(const struct sock *sk, struct sock *newsk);
+#else
+static inline int bpf_sk_storage_clone(const struct sock *sk,
+ struct sock *newsk)
+{
+ return 0;
+}
+#endif
+
#endif /* _BPF_SK_STORAGE_H */
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -337,6 +337,9 @@ enum bpf_attach_type {
#define BPF_F_RDONLY_PROG (1U << 7)
#define BPF_F_WRONLY_PROG (1U << 8)
+/* Clone map from listener for newly accepted socket */
+#define BPF_F_CLONE (1U << 9)
+
/* flags for BPF_PROG_QUERY */
#define BPF_F_QUERY_EFFECTIVE (1U << 0)
--- a/net/core/bpf_sk_storage.c
+++ b/net/core/bpf_sk_storage.c
@@ -12,6 +12,9 @@
static atomic_t cache_idx;
+#define SK_STORAGE_CREATE_FLAG_MASK \
+ (BPF_F_NO_PREALLOC | BPF_F_CLONE)
+
struct bucket {
struct hlist_head list;
raw_spinlock_t lock;
@@ -209,7 +212,6 @@ static void selem_unlink_sk(struct bpf_s
kfree_rcu(sk_storage, rcu);
}
-/* sk_storage->lock must be held and sk_storage->list cannot be empty */
static void __selem_link_sk(struct bpf_sk_storage *sk_storage,
struct bpf_sk_storage_elem *selem)
{
@@ -509,7 +511,7 @@ static int sk_storage_delete(struct sock
return 0;
}
-/* Called by __sk_destruct() */
+/* Called by __sk_destruct() & bpf_sk_storage_clone() */
void bpf_sk_storage_free(struct sock *sk)
{
struct bpf_sk_storage_elem *selem;
@@ -557,6 +559,11 @@ static void bpf_sk_storage_map_free(stru
smap = (struct bpf_sk_storage_map *)map;
+ /* Note that this map might be concurrently cloned from
+ * bpf_sk_storage_clone. Wait for any existing bpf_sk_storage_clone
+ * RCU read section to finish before proceeding. New RCU
+ * read sections should be prevented via bpf_map_inc_not_zero.
+ */
synchronize_rcu();
/* bpf prog and the userspace can no longer access this map
@@ -601,7 +608,9 @@ static void bpf_sk_storage_map_free(stru
static int bpf_sk_storage_map_alloc_check(union bpf_attr *attr)
{
- if (attr->map_flags != BPF_F_NO_PREALLOC || attr->max_entries ||
+ if (attr->map_flags & ~SK_STORAGE_CREATE_FLAG_MASK ||
+ !(attr->map_flags & BPF_F_NO_PREALLOC) ||
+ attr->max_entries ||
attr->key_size != sizeof(int) || !attr->value_size ||
/* Enforce BTF for userspace sk dumping */
!attr->btf_key_type_id || !attr->btf_value_type_id)
@@ -739,6 +748,95 @@ static int bpf_fd_sk_storage_delete_elem
return err;
}
+static struct bpf_sk_storage_elem *
+bpf_sk_storage_clone_elem(struct sock *newsk,
+ struct bpf_sk_storage_map *smap,
+ struct bpf_sk_storage_elem *selem)
+{
+ struct bpf_sk_storage_elem *copy_selem;
+
+ copy_selem = selem_alloc(smap, newsk, NULL, true);
+ if (!copy_selem)
+ return NULL;
+
+ if (map_value_has_spin_lock(&smap->map))
+ copy_map_value_locked(&smap->map, SDATA(copy_selem)->data,
+ SDATA(selem)->data, true);
+ else
+ copy_map_value(&smap->map, SDATA(copy_selem)->data,
+ SDATA(selem)->data);
+
+ return copy_selem;
+}
+
+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 = 0;
+
+ 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;
+
+ smap = rcu_dereference(SDATA(selem)->smap);
+ if (!(smap->map.map_flags & BPF_F_CLONE))
+ continue;
+
+ /* Note that for lockless listeners adding new element
+ * here can race with cleanup in bpf_sk_storage_map_free.
+ * Try to grab map refcnt to make sure that it's still
+ * alive and prevent concurrent removal.
+ */
+ 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 out;
+ }
+
+ 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 out;
+ }
+
+ new_sk_storage = rcu_dereference(copy_selem->sk_storage);
+ }
+ bpf_map_put(map);
+ }
+
+out:
+ rcu_read_unlock();
+
+ /* In case of an error, don't free anything explicitly here, the
+ * caller is responsible to call bpf_sk_storage_free.
+ */
+
+ return ret;
+}
+
BPF_CALL_4(bpf_sk_storage_get, struct bpf_map *, map, struct sock *, sk,
void *, value, u64, flags)
{
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1851,9 +1851,12 @@ struct sock *sk_clone_lock(const struct
goto out;
}
RCU_INIT_POINTER(newsk->sk_reuseport_cb, NULL);
-#ifdef CONFIG_BPF_SYSCALL
- RCU_INIT_POINTER(newsk->sk_bpf_storage, NULL);
-#endif
+
+ if (bpf_sk_storage_clone(sk, newsk)) {
+ sk_free_unlock_clone(newsk);
+ newsk = NULL;
+ goto out;
+ }
newsk->sk_err = 0;
newsk->sk_err_soft = 0;