[PATCH net-next v2 4/8] tls: honor O_NONBLOCK in tls_sw_splice_read()

[Chuck Lever <cel@kernel.org>]

tls_sw_splice_read() takes its blocking behavior from
SPLICE_F_NONBLOCK alone. When splicing from a socket to a pipe,
do_splice() sets that flag from the pipe's O_NONBLOCK, not the
socket's. On a nonblocking socket, a splice(2) call without
SPLICE_F_NONBLOCK therefore sleeps in tls_rx_rec_wait() until a
record arrives. tcp_splice_read() instead reads sock->file->f_flags
and returns -EAGAIN.

Poll makes the sleep reachable. tls_sw_sock_is_readable() reports
the socket readable while any record sits on rx_list, including a
zero-length record that delivers no bytes to the pipe. The
strparser announces a record before decryption, when its plaintext
length is unknown, so the readiness test cannot screen such a
record out. The splice consumes it and waits for the next, and an
event loop that polls and then splices stalls every connection it
multiplexes.

Treat the socket's O_NONBLOCK as nonblocking too. A caller that
sets O_NONBLOCK and splices without SPLICE_F_NONBLOCK, taking that
flag to govern only the pipe, now gets -EAGAIN where it blocked
before. sendfile(2) from a TLS socket changes the same way, because
do_sendfile() leaves the input file's O_NONBLOCK out of the splice
flags. Both now behave as they do on a plain TCP socket.

Fixes: c46234ebb4d1 ("tls: RX path for ktls")
Signed-off-by: Chuck Lever <cel@kernel.org>
---
 net/tls/tls_sw.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index 79a807e51bc7..6ca1e9f4e504 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -2020,10 +2020,14 @@ ssize_t tls_sw_splice_read(struct socket *sock,  loff_t *ppos,
 	struct sk_buff *skb;
 	bool released = true;
 	ssize_t copied = 0;
+	bool nonblock;
 	int chunk;
 	int err;
 
-	err = tls_rx_reader_lock(sk, ctx, flags & SPLICE_F_NONBLOCK);
+	nonblock = (flags & SPLICE_F_NONBLOCK) ||
+		   (sock->file->f_flags & O_NONBLOCK);
+
+	err = tls_rx_reader_lock(sk, ctx, nonblock);
 	if (err < 0)
 		return err;
 
@@ -2038,8 +2042,7 @@ ssize_t tls_sw_splice_read(struct socket *sock,  loff_t *ppos,
 	} else {
 		struct tls_decrypt_arg darg;
 
-		err = tls_rx_rec_wait(sk, flags & SPLICE_F_NONBLOCK,
-				      released, false);
+		err = tls_rx_rec_wait(sk, nonblock, released, false);
 		if (err <= 0)
 			goto splice_read_end;
 
@@ -2069,10 +2072,7 @@ ssize_t tls_sw_splice_read(struct socket *sock,  loff_t *ppos,
 	if (rxm->full_len == 0) {
 		consume_skb(skb);
 		if (signal_pending(current)) {
-			long timeo;
-
-			timeo = sock_rcvtimeo(sk, flags & SPLICE_F_NONBLOCK);
-			err = sock_intr_errno(timeo);
+			err = sock_intr_errno(sock_rcvtimeo(sk, nonblock));
 			goto splice_read_end;
 		}
 		goto retry;

-- 
2.55.0