[PATCH net-next v3 1/3] net/tls: use RCU protection on icsk->icsk_ulp_data

[Davide Caratti <dcaratti@redhat.com>]

From: Jakub Kicinski <jakub.kicinski@netronome.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@netronome.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                 | 26 +++++++++++++++++++-------
 5 files changed, 29 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 a470df7ffcf9..e188139f0464 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 43252a801c3f..f8f2d2c3d627 100644
--- a/net/tls/tls_main.c
+++ b/net/tls/tls_main.c
@@ -251,14 +251,26 @@ 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)
 {
 	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)
+		kfree_rcu(ctx, rcu);
+	else
+		kfree(ctx);
 }
 
 static void tls_sk_proto_cleanup(struct sock *sk,
@@ -306,7 +318,7 @@ 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;
 	if (sk->sk_write_space == tls_write_space)
 		sk->sk_write_space = ctx->sk_write_space;
@@ -321,7 +333,7 @@ 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,
@@ -610,7 +622,7 @@ 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;
@@ -651,8 +663,8 @@ static void tls_hw_sk_destruct(struct sock *sk)
 
 	ctx->sk_destruct(sk);
 	/* Free ctx */
-	tls_ctx_free(ctx);
-	icsk->icsk_ulp_data = NULL;
+	rcu_assign_pointer(icsk->icsk_ulp_data, NULL);
+	tls_ctx_free(sk, ctx);
 }
 
 static int tls_hw_prot(struct sock *sk)
-- 
2.20.1