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

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Message-ID: <pdgrhpta6qqwa7r6zexqikcybkllootq7qwbe36i5uf3fpbavb@v4vyiclg2cis>
Date: Fri, 25 Oct 2024 10:37:49 +0200
From: Stefano Garzarella <sgarzare@...hat.com>
To: Konstantin Shkolnyy <kshk@...ux.ibm.com>
Cc: virtualization@...ts.linux.dev, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org, mjrosato@...ux.ibm.com
Subject: Re: [PATCH v2] vsock/test: fix failures due to wrong SO_RCVLOWAT
 parameter

On Thu, Oct 24, 2024 at 11:10:58AM -0500, Konstantin Shkolnyy wrote:
>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

LGTM!

Reviewed-by: Stefano Garzarella <sgarzare@...hat.com>

>
> 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
>