[PATCH] tls: don't abort the connection on signal-interrupted sends

[Maximilian Immanuel Brandtner <maxbr@linux.ibm.com>]

When a signal interrupts a blocking send, tls_tx_records() treats the
resulting -ERESTARTSYS as a transmission failure and marks the socket
errored via tls_err_abort() with the raw error code. Later syscalls
return the kernel-internal errno 512 (ERESTARTSYS) to userspace, as the
signal it stems from is no longer pending during syscall exit and thus
never translated.

An interrupted send is not a connection error: the partially sent record
stays queued and is resent later. Interrupt error codes are therefore
excluded from the abort in the same way as -EAGAIN.

Fixes: b341ca51d267 ("tls: Fix tls_sw_sendmsg error handling")
Signed-off-by: Maximilian Immanuel Brandtner <maxbr@linux.ibm.com>
---
Tested on top of net commit 3f1f75536668 ("net: openvswitch: reject
oversized nested action attrs").

Several subsystems contain static helper functions to classify these
interrupt errnos. It might be worthwhile to refactor these static
functions into a generic helper function.
---
 net/tls/tls_sw.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index d4afc90fd796..3c9e94069e82 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -405,6 +405,24 @@ static void tls_free_open_rec(struct sock *sk)
 	}
 }
 
+static bool tls_is_non_restartable_err(int err)
+{
+	if (err >= 0)
+		return false;
+
+	switch (err) {
+	case -EAGAIN:
+	case -EINTR:
+	case -ERESTARTSYS:
+	case -ERESTARTNOINTR:
+	case -ERESTARTNOHAND:
+	case -ERESTART_RESTARTBLOCK:
+		return false;
+	default:
+		return true;
+	}
+}
+
 int tls_tx_records(struct sock *sk, int flags)
 {
 	struct tls_context *tls_ctx = tls_get_ctx(sk);
@@ -458,7 +476,7 @@ int tls_tx_records(struct sock *sk, int flags)
 	}
 
 tx_err:
-	if (rc < 0 && rc != -EAGAIN)
+	if (tls_is_non_restartable_err(rc))
 		tls_err_abort(sk, rc);
 
 	return rc;
-- 
2.55.0