[LTP] [PATCH] sysctl/sysctl03: Test whether return EINVAL when passing negative value

[xuyang2018.jy@fujitsu.com]

Hi Cyril
> Hi!
>> +#!/bin/sh
>> +# SPDX-License-Identifier: GPL-2.0-or-later
>> +# Copyright (c) 2022 FUJITSU LIMITED. All rights reserved.
>> +# Author: Yang Xu<xuyang2018.jy@fujitsu.com>
>> +#
>> +# When we pass a negative value to the proc_doulongvec_minmax() function,
>> +# the function should return EINVAL and the corresponding interface value
>> +# does not change.
>> +#
>> +# It is also a regression test for
>> +# commit 1622ed7d0743 ("sysctl: returns -EINVAL when a negative value is passed
>> +# to proc_doulongvec_minmax").
>> +#
>> +# Use fs.epoll.max_user_watches interface to test this.
>> +
>> +TST_TESTFUNC=do_test
>> +TST_SETUP=setup
>> +TST_NEEDS_ROOT=1
>> +TST_NEEDS_CMDS="sysctl"
>> +TST_NEEDS_KCONFIGS="CONFIG_SYSCTL=y, CONFIG_PROC_FS=y, CONFIG_INOTIFY_USER=y"
>> +sys_name="fs.epoll.max_user_watches"
>> +sys_file="/proc/sys/fs/epoll/max_user_watches"
>> +
>> +. tst_test.sh
>> +
>> +setup()
>> +{
>> +	orig_value=$(cat "$sys_file")
>> +}
>> +
>> +do_test()
>> +{
>> +	tst_res TINFO "trying to set $sys_name=-1"
>> +
>> +	sysctl -w -q $sys_name=-1 2>&1 | grep -q "Invalid argument"
>> +
>> +	if [ $? -eq 0 ]; then
>> +		tst_res TPASS "sysctl returns EINVAL when passing a negative value"
>> +	else
>> +		tst_res TFAIL "sysctl doesn't return EINVAL when passing a negative value"
>> +	fi
>> +
>> +	new_value=$(cat "$sys_file")
>> +	if [ $orig_value -eq $new_value ]; then
>> +		tst_res TPASS "the interface value doesn't change when passing a negative value"
>> +	else
>> +		tst_res TFAIL "the interface value changes when passing a negative value"
>> +		sysctl -w -q $sys_name=$orig_value
>> +	fi
>> +}
>> +
>> +tst_run
>
> I'm just wondering if this wouldn't be actually easier as a C test. I
> bet that simple write() to the sys_file would work exactly the same and
> we wouldn't depend on sysctl being present on the system.
If using C program, it seems not have a suitable place to put this test 
case. Do you have some advise?

Best Regards
Yang Xu
>