Re: [PATCH bpf-next v3 2/4] bpf: support cloning sk storage on accept()

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 




On 8/13/19 9:26 AM, 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@xxxxxx>
> Cc: Yonghong Song <yhs@xxxxxx>
> Acked-by: Yonghong Song <yhs@xxxxxx>
> Signed-off-by: Stanislav Fomichev <sdf@xxxxxxxxxx>
> ---
>   include/net/bpf_sk_storage.h |  10 ++++
>   include/uapi/linux/bpf.h     |   3 +
>   net/core/bpf_sk_storage.c    | 103 ++++++++++++++++++++++++++++++++++-
>   net/core/sock.c              |   9 ++-
>   4 files changed, 119 insertions(+), 6 deletions(-)
> 
> diff --git a/include/net/bpf_sk_storage.h b/include/net/bpf_sk_storage.h
> index b9dcb02e756b..8e4f831d2e52 100644
> --- 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 */
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 4393bd4b2419..0ef594ac3899 100644
> --- 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)
>   
> diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c
> index 94c7f77ecb6b..1bc7de7e18ba 100644
> --- 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_sk_storage_elem *selem)
>   		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 *sk, struct bpf_map *map)
>   	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(struct bpf_map *map)
>   
>   	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(struct bpf_map *map)
>   
>   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 +748,94 @@ static int bpf_fd_sk_storage_delete_elem(struct bpf_map *map, void *key)
>   	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;
> +
> +	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;
> +
> +		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);
> +	}
> +
> +out:
> +	rcu_read_unlock();
> +	return 0;
> +
> +err:
> +	rcu_read_unlock();
> +
> +	/* Don't free anything explicitly here, caller is responsible to
> +	 * call bpf_sk_storage_free in case of an error.
> +	 */
> +
> +	return ret;

A nit.
If you set ret = 0 initially, you do not need the above two 
rcu_read_unlock(). One "return ret" should be enough.
The comment can be changed to
	/* In case of an error, ... */


> +}
> +
>   BPF_CALL_4(bpf_sk_storage_get, struct bpf_map *, map, struct sock *, sk,
>   	   void *, value, u64, flags)
>   {
> diff --git a/net/core/sock.c b/net/core/sock.c
> index d57b0cc995a0..f5e801a9cea4 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -1851,9 +1851,12 @@ struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority)
>   			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;
> 




[Index of Archives]     [Linux Samsung SoC]     [Linux Rockchip SoC]     [Linux Actions SoC]     [Linux for Synopsys ARC Processors]     [Linux NFS]     [Linux NILFS]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]


  Powered by Linux