netdev - [PATCH net] net/tls: Inform user space about send buffer availability

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Date:   Tue, 12 Mar 2019 07:09:51 +0000
From:   Vakul Garg <vakul.garg@....com>
To:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     "borisp@...lanox.com" <borisp@...lanox.com>,
        "aviadye@...lanox.com" <aviadye@...lanox.com>,
        "davejwatson@...com" <davejwatson@...com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "doronrk@...com" <doronrk@...com>, Vakul Garg <vakul.garg@....com>
Subject: [PATCH net] net/tls: Inform user space about send buffer availability

A previous fix ("tls: Fix write space handling") assumed that
user space application gets informed about the socket send buffer
availability when tls_push_sg() gets called. Inside tls_push_sg(), in
case do_tcp_sendpages() returns 0, the function returns without calling
ctx->sk_write_space. Further, the new function tls_sw_write_space()
did not invoke ctx->sk_write_space. This leads to situation that user
space application encounters a lockup always waiting for socket send
buffer to become available.

Rather than call ctx->sk_write_space from tls_push_sg(), it should be
called from tls_sw_write_space. So whenever tcp stack invokes
sk->sk_write_space after freeing socket send buffer, we always declare
the same to user space by the way of invoking ctx->sk_write_space. The
function tls_device_write_space() already invokes ctx->sk_write_space.

Fixes: 7463d3a2db0ef ("tls: Fix write space handling")
Signed-off-by: Vakul Garg <vakul.garg@....com>
---
 net/tls/tls_main.c | 1 -
 net/tls/tls_sw.c   | 2 ++
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c
index 17e8667917aa..1d16562f86ed 100644
--- a/net/tls/tls_main.c
+++ b/net/tls/tls_main.c
@@ -146,7 +146,6 @@ int tls_push_sg(struct sock *sk,
 	}

 	ctx->in_tcp_sendpages = false;
-	ctx->sk_write_space(sk);

 	return 0;
 }
diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index 425351ac2a9b..3d9f4cc0bb9c 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -2143,6 +2143,8 @@ void tls_sw_write_space(struct sock *sk, struct tls_context *ctx)
 				      &tx_ctx->tx_bitmask))
 			schedule_delayed_work(&tx_ctx->tx_work.work, 0);
 	}
+
+	ctx->sk_write_space(sk);
 }

 int tls_set_sw_offload(struct sock *sk, struct tls_context *ctx, int tx)
-- 
2.13.6