From 79ffe6087e9145d2377385cac48d0d6a6b4225a5 Mon Sep 17 00:00:00 2001 From: Jakub Kicinski Date: Tue, 5 Nov 2019 14:24:35 -0800 Subject: 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: a42055e8d2c3 ("net/tls: Add support for async encryption of records for performance") Reported-by: Mallesham Jatharakonda Reported-by: Pooja Trivedi Signed-off-by: Jakub Kicinski Reviewed-by: Simon Horman Signed-off-by: David S. Miller --- net/tls/tls_sw.c | 21 +++++++-------------- 1 file changed, 7 insertions(+), 14 deletions(-) (limited to 'net/tls/tls_sw.c') diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c index e155b792df0b..446f23c1f3ce 100644 --- a/net/tls/tls_sw.c +++ b/net/tls/tls_sw.c @@ -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) -- cgit