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Date: Thu, 15 Aug 2019 14:32:16 -0700
From: Jakub Kicinski <jakub.kicinski@...ronome.com>
To: Davide Caratti <dcaratti@...hat.com>
Cc: Boris Pismenny <borisp@...lanox.com>,
John Fastabend <john.fastabend@...il.com>,
Dave Watson <davejwatson@...com>,
Aviad Yehezkel <aviadye@...lanox.com>,
"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 1/3] net/tls: use RCU protection on
icsk->icsk_ulp_data
On Thu, 15 Aug 2019 18:00:42 +0200, Davide Caratti wrote:
> From: Jakub Kicinski <jakub.kicinski@...ronome.com>
>
> We need to make sure context does not get freed while diag
> code is interrogating it. Free struct tls_context with
> kfree_rcu().
>
> We add the __rcu annotation directly in icsk, and cast it
> away in the datapath accessor. Presumably all ULPs will
> do a similar thing.
>
> Signed-off-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
> ---
> include/net/inet_connection_sock.h | 2 +-
> include/net/tls.h | 9 +++++++--
> net/core/sock_map.c | 2 +-
> net/tls/tls_device.c | 2 +-
> net/tls/tls_main.c | 31 +++++++++++++++++++++++-------
> 5 files changed, 34 insertions(+), 12 deletions(-)
>
> diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h
> index c57d53e7e02c..895546058a20 100644
> --- a/include/net/inet_connection_sock.h
> +++ b/include/net/inet_connection_sock.h
> @@ -97,7 +97,7 @@ struct inet_connection_sock {
> const struct tcp_congestion_ops *icsk_ca_ops;
> const struct inet_connection_sock_af_ops *icsk_af_ops;
> const struct tcp_ulp_ops *icsk_ulp_ops;
> - void *icsk_ulp_data;
> + void __rcu *icsk_ulp_data;
> void (*icsk_clean_acked)(struct sock *sk, u32 acked_seq);
> struct hlist_node icsk_listen_portaddr_node;
> unsigned int (*icsk_sync_mss)(struct sock *sk, u32 pmtu);
> diff --git a/include/net/tls.h b/include/net/tls.h
> index 41b2d41bb1b8..4997742475cd 100644
> --- a/include/net/tls.h
> +++ b/include/net/tls.h
> @@ -41,6 +41,7 @@
> #include <linux/tcp.h>
> #include <linux/skmsg.h>
> #include <linux/netdevice.h>
> +#include <linux/rcupdate.h>
>
> #include <net/tcp.h>
> #include <net/strparser.h>
> @@ -290,6 +291,7 @@ struct tls_context {
>
> struct list_head list;
> refcount_t refcount;
> + struct rcu_head rcu;
> };
>
> enum tls_offload_ctx_dir {
> @@ -348,7 +350,7 @@ struct tls_offload_context_rx {
> #define TLS_OFFLOAD_CONTEXT_SIZE_RX \
> (sizeof(struct tls_offload_context_rx) + TLS_DRIVER_STATE_SIZE_RX)
>
> -void tls_ctx_free(struct tls_context *ctx);
> +void tls_ctx_free(struct sock *sk, struct tls_context *ctx);
> int wait_on_pending_writer(struct sock *sk, long *timeo);
> int tls_sk_query(struct sock *sk, int optname, char __user *optval,
> int __user *optlen);
> @@ -467,7 +469,10 @@ static inline struct tls_context *tls_get_ctx(const struct sock *sk)
> {
> struct inet_connection_sock *icsk = inet_csk(sk);
>
> - return icsk->icsk_ulp_data;
> + /* Use RCU on icsk_ulp_data only for sock diag code,
> + * TLS data path doesn't need rcu_dereference().
> + */
> + return (__force void *)icsk->icsk_ulp_data;
> }
>
> static inline void tls_advance_record_sn(struct sock *sk,
> diff --git a/net/core/sock_map.c b/net/core/sock_map.c
> index 1330a7442e5b..01998860afaa 100644
> --- a/net/core/sock_map.c
> +++ b/net/core/sock_map.c
> @@ -345,7 +345,7 @@ static int sock_map_update_common(struct bpf_map *map, u32 idx,
> return -EINVAL;
> if (unlikely(idx >= map->max_entries))
> return -E2BIG;
> - if (unlikely(icsk->icsk_ulp_data))
> + if (unlikely(rcu_access_pointer(icsk->icsk_ulp_data)))
> return -EINVAL;
>
> link = sk_psock_init_link();
> diff --git a/net/tls/tls_device.c b/net/tls/tls_device.c
> index d184230665eb..436df5b4bb60 100644
> --- a/net/tls/tls_device.c
> +++ b/net/tls/tls_device.c
> @@ -61,7 +61,7 @@ static void tls_device_free_ctx(struct tls_context *ctx)
> if (ctx->rx_conf == TLS_HW)
> kfree(tls_offload_ctx_rx(ctx));
>
> - tls_ctx_free(ctx);
> + tls_ctx_free(NULL, ctx);
> }
>
> static void tls_device_gc_task(struct work_struct *work)
> diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c
> index 9cbbae606ced..04829bef514c 100644
> --- a/net/tls/tls_main.c
> +++ b/net/tls/tls_main.c
> @@ -251,14 +251,31 @@ static void tls_write_space(struct sock *sk)
> ctx->sk_write_space(sk);
> }
>
> -void tls_ctx_free(struct tls_context *ctx)
> +/**
> + * tls_ctx_free() - free TLS ULP context
> + * @sk: socket to with @ctx is attached
> + * @ctx: TLS context structure
> + *
> + * Free TLS context. If @sk is %NULL caller guarantees that the socket
> + * to which @ctx was attached has no outstanding references.
> + */
> +void tls_ctx_free(struct sock *sk, struct tls_context *ctx)
> {
> + struct inet_connection_sock *icsk;
> +
> if (!ctx)
> return;
>
> memzero_explicit(&ctx->crypto_send, sizeof(ctx->crypto_send));
> memzero_explicit(&ctx->crypto_recv, sizeof(ctx->crypto_recv));
> - kfree(ctx);
> +
> + if (sk) {
> + icsk = inet_csk(sk);
> + rcu_assign_pointer(icsk->icsk_ulp_data, NULL);
Now that we kind of want to set the icsk_ulp_data to NULL under the
callback_lock I think we should let the callers do it.
> + kfree_rcu(ctx, rcu);
> + } else {
> + kfree(ctx);
> + }
> }
>
> static void tls_sk_proto_cleanup(struct sock *sk,
> @@ -306,7 +323,7 @@ static void tls_sk_proto_close(struct sock *sk, long timeout)
>
> write_lock_bh(&sk->sk_callback_lock);
> if (free_ctx)
> - icsk->icsk_ulp_data = NULL;
> + rcu_assign_pointer(icsk->icsk_ulp_data, NULL);
> sk->sk_prot = ctx->sk_proto;
> write_unlock_bh(&sk->sk_callback_lock);
> release_sock(sk);
> @@ -319,7 +336,7 @@ static void tls_sk_proto_close(struct sock *sk, long timeout)
> ctx->sk_proto_close(sk, timeout);
>
> if (free_ctx)
> - tls_ctx_free(ctx);
> + tls_ctx_free(sk, ctx);
> }
>
> static int do_tls_getsockopt_tx(struct sock *sk, char __user *optval,
> @@ -608,7 +625,7 @@ static struct tls_context *create_ctx(struct sock *sk)
> if (!ctx)
> return NULL;
>
> - icsk->icsk_ulp_data = ctx;
> + rcu_assign_pointer(icsk->icsk_ulp_data, ctx);
> ctx->setsockopt = sk->sk_prot->setsockopt;
> ctx->getsockopt = sk->sk_prot->getsockopt;
> ctx->sk_proto_close = sk->sk_prot->close;
> @@ -649,8 +666,8 @@ static void tls_hw_sk_destruct(struct sock *sk)
>
> ctx->sk_destruct(sk);
> /* Free ctx */
> - tls_ctx_free(ctx);
> - icsk->icsk_ulp_data = NULL;
> + tls_ctx_free(sk, ctx);
> + rcu_assign_pointer(icsk->icsk_ulp_data, NULL);
Let's reorder the assignment before the free.
> }
>
> static int tls_hw_prot(struct sock *sk)
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