netdev - [PATCH v2] vsock/test: fix failures due to wrong SO

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Message-Id: <20241024161058.435469-1-kshk@linux.ibm.com>
Date: Thu, 24 Oct 2024 11:10:58 -0500
From: Konstantin Shkolnyy <kshk@...ux.ibm.com>
To: sgarzare@...hat.com
Cc: virtualization@...ts.linux.dev, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, mjrosato@...ux.ibm.com,
        Konstantin Shkolnyy <kshk@...ux.ibm.com>
Subject: [PATCH v2] vsock/test: fix failures due to wrong SO_RCVLOWAT parameter

This happens on 64-bit big-endian machines.
SO_RCVLOWAT requires an int parameter. However, instead of int, the test
uses unsigned long in one place and size_t in another. Both are 8 bytes
long on 64-bit machines. The kernel, having received the 8 bytes, doesn't
test for the exact size of the parameter, it only cares that it's >=
sizeof(int), and casts the 4 lower-addressed bytes to an int, which, on
a big-endian machine, contains 0. 0 doesn't trigger an error, SO_RCVLOWAT
returns with success and the socket stays with the default SO_RCVLOWAT = 1,
which results in test failures.

Fixes: b1346338fbae ("vsock_test: POLLIN + SO_RCVLOWAT test")
Fixes: 542e893fbadc ("vsock/test: two tests to check credit update logic")
Signed-off-by: Konstantin Shkolnyy <kshk@...ux.ibm.com>
---

Notes:
    The problem was found on s390 (big endian), while x86-64 didn't show it. After this fix, all tests pass on s390.
Changes for v2:
- add "Fixes:" lines to the commit message

 tools/testing/vsock/vsock_test.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/testing/vsock/vsock_test.c b/tools/testing/vsock/vsock_test.c
index 8d38dbf8f41f..7fd25b814b4b 100644
--- a/tools/testing/vsock/vsock_test.c
+++ b/tools/testing/vsock/vsock_test.c
@@ -835,7 +835,7 @@ static void test_stream_poll_rcvlowat_server(const struct test_opts *opts)
 
 static void test_stream_poll_rcvlowat_client(const struct test_opts *opts)
 {
-	unsigned long lowat_val = RCVLOWAT_BUF_SIZE;
+	int lowat_val = RCVLOWAT_BUF_SIZE;
 	char buf[RCVLOWAT_BUF_SIZE];
 	struct pollfd fds;
 	short poll_flags;
@@ -1357,7 +1357,7 @@ static void test_stream_rcvlowat_def_cred_upd_client(const struct test_opts *opt
 static void test_stream_credit_update_test(const struct test_opts *opts,
 					   bool low_rx_bytes_test)
 {
-	size_t recv_buf_size;
+	int recv_buf_size;
 	struct pollfd fds;
 	size_t buf_size;
 	void *buf;
-- 
2.34.1