Commit 79ffe608 authored by Jakub Kicinski's avatar Jakub Kicinski Committed by David S. Miller
Browse files

net/tls: add a TX lock 



TLS TX needs to release and re-acquire the socket lock if send buffer
fills up.

TLS SW TX path currently depends on only allowing one thread to enter
the function by the abuse of sk_write_pending. If another writer is
already waiting for memory no new ones are allowed in.

This has two problems:
 - writers don't wake other threads up when they leave the kernel;
   meaning that this scheme works for single extra thread (second
   application thread or delayed work) because memory becoming
   available will send a wake up request, but as Mallesham and
   Pooja report with larger number of threads it leads to threads
   being put to sleep indefinitely;
 - the delayed work does not get _scheduled_ but it may _run_ when
   other writers are present leading to crashes as writers don't
   expect state to change under their feet (same records get pushed
   and freed multiple times); it's hard to reliably bail from the
   work, however, because the mere presence of a writer does not
   guarantee that the writer will push pending records before exiting.

Ensuring wakeups always happen will make the code basically open
code a mutex. Just use a mutex.

The TLS HW TX path does not have any locking (not even the
sk_write_pending hack), yet it uses a per-socket sg_tx_data
array to push records.

Fixes: a42055e8 ("net/tls: Add support for async encryption of records for performance")
Reported-by: default avatarMallesham Jatharakonda <mallesh537@gmail.com>
Reported-by: default avatarPooja Trivedi <poojatrivedi@gmail.com>
Signed-off-by: default avatarJakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: default avatarSimon Horman <simon.horman@netronome.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 02b1fa07

include/net/tls.h

+5 −0
Original line number Diff line number Diff line
@@ -40,6 +40,7 @@ 
#include <linux/socket.h>

#include <linux/tcp.h>

#include <linux/skmsg.h>

#include <linux/mutex.h>

#include <linux/netdevice.h>

#include <linux/rcupdate.h>
@@ -269,6 +270,10 @@ struct tls_context { 


	bool in_tcp_sendpages;

	bool pending_open_record_frags;



	struct mutex tx_lock; /* protects partially_sent_* fields and

			       * per-type TX fields

			       */

	unsigned long flags;



	/* cache cold stuff */

net/tls/tls_device.c

+6 −0
Original line number Diff line number Diff line
@@ -523,8 +523,10 @@ last_record: 
int tls_device_sendmsg(struct sock *sk, struct msghdr *msg, size_t size)

{

	unsigned char record_type = TLS_RECORD_TYPE_DATA;

	struct tls_context *tls_ctx = tls_get_ctx(sk);

	int rc;



	mutex_lock(&tls_ctx->tx_lock);

	lock_sock(sk);



	if (unlikely(msg->msg_controllen)) {
@@ -538,12 +540,14 @@ int tls_device_sendmsg(struct sock *sk, struct msghdr *msg, size_t size) 


out:

	release_sock(sk);

	mutex_unlock(&tls_ctx->tx_lock);

	return rc;

}



int tls_device_sendpage(struct sock *sk, struct page *page,

			int offset, size_t size, int flags)

{

	struct tls_context *tls_ctx = tls_get_ctx(sk);

	struct iov_iter	msg_iter;

	char *kaddr = kmap(page);

	struct kvec iov;
@@ -552,6 +556,7 @@ int tls_device_sendpage(struct sock *sk, struct page *page, 
	if (flags & MSG_SENDPAGE_NOTLAST)

		flags |= MSG_MORE;



	mutex_lock(&tls_ctx->tx_lock);

	lock_sock(sk);



	if (flags & MSG_OOB) {
@@ -568,6 +573,7 @@ int tls_device_sendpage(struct sock *sk, struct page *page, 


out:

	release_sock(sk);

	mutex_unlock(&tls_ctx->tx_lock);

	return rc;

}

net/tls/tls_main.c

+2 −0
Original line number Diff line number Diff line
@@ -267,6 +267,7 @@ void tls_ctx_free(struct sock *sk, struct tls_context *ctx) 


	memzero_explicit(&ctx->crypto_send, sizeof(ctx->crypto_send));

	memzero_explicit(&ctx->crypto_recv, sizeof(ctx->crypto_recv));

	mutex_destroy(&ctx->tx_lock);



	if (sk)

		kfree_rcu(ctx, rcu);
@@ -612,6 +613,7 @@ static struct tls_context *create_ctx(struct sock *sk) 
	if (!ctx)

		return NULL;



	mutex_init(&ctx->tx_lock);

	rcu_assign_pointer(icsk->icsk_ulp_data, ctx);

	ctx->sk_proto = sk->sk_prot;

	return ctx;

net/tls/tls_sw.c

+7 −14
Original line number Diff line number Diff line
@@ -897,15 +897,9 @@ int tls_sw_sendmsg(struct sock *sk, struct msghdr *msg, size_t size) 
	if (msg->msg_flags & ~(MSG_MORE | MSG_DONTWAIT | MSG_NOSIGNAL))

		return -ENOTSUPP;



	mutex_lock(&tls_ctx->tx_lock);

	lock_sock(sk);



	/* Wait till there is any pending write on socket */

	if (unlikely(sk->sk_write_pending)) {

		ret = wait_on_pending_writer(sk, &timeo);

		if (unlikely(ret))

			goto send_end;

	}



	if (unlikely(msg->msg_controllen)) {

		ret = tls_proccess_cmsg(sk, msg, &record_type);

		if (ret) {
@@ -1091,6 +1085,7 @@ send_end: 
	ret = sk_stream_error(sk, msg->msg_flags, ret);



	release_sock(sk);

	mutex_unlock(&tls_ctx->tx_lock);

	return copied ? copied : ret;

}
@@ -1114,13 +1109,6 @@ static int tls_sw_do_sendpage(struct sock *sk, struct page *page, 
	eor = !(flags & (MSG_MORE | MSG_SENDPAGE_NOTLAST));

	sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk);



	/* Wait till there is any pending write on socket */

	if (unlikely(sk->sk_write_pending)) {

		ret = wait_on_pending_writer(sk, &timeo);

		if (unlikely(ret))

			goto sendpage_end;

	}



	/* Call the sk_stream functions to manage the sndbuf mem. */

	while (size > 0) {

		size_t copy, required_size;
@@ -1219,15 +1207,18 @@ sendpage_end: 
int tls_sw_sendpage(struct sock *sk, struct page *page,

		    int offset, size_t size, int flags)

{

	struct tls_context *tls_ctx = tls_get_ctx(sk);

	int ret;



	if (flags & ~(MSG_MORE | MSG_DONTWAIT | MSG_NOSIGNAL |

		      MSG_SENDPAGE_NOTLAST | MSG_SENDPAGE_NOPOLICY))

		return -ENOTSUPP;



	mutex_lock(&tls_ctx->tx_lock);

	lock_sock(sk);

	ret = tls_sw_do_sendpage(sk, page, offset, size, flags);

	release_sock(sk);

	mutex_unlock(&tls_ctx->tx_lock);

	return ret;

}
@@ -2170,9 +2161,11 @@ static void tx_work_handler(struct work_struct *work) 


	if (!test_and_clear_bit(BIT_TX_SCHEDULED, &ctx->tx_bitmask))

		return;

	mutex_lock(&tls_ctx->tx_lock);

	lock_sock(sk);

	tls_tx_records(sk, -1);

	release_sock(sk);

	mutex_unlock(&tls_ctx->tx_lock);

}



void tls_sw_write_space(struct sock *sk, struct tls_context *ctx)

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