linux-kernel - Re: [PATCH] modpost: abort if a module name is too long

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Message-ID: <e29e1858-7509-5e9f-9e71-169da18033e5@huawei.com>
Date:   Wed, 31 May 2017 11:48:56 +0800
From:   Wanlong Gao <gaowanlong@...wei.com>
To:     Jessica Yu <jeyu@...hat.com>
CC:     <gaowanlong@...wei.com>, Xie XiuQi <xiexiuqi@...wei.com>,
        <akpm@...ux-foundation.org>, <linux-kernel@...r.kernel.org>,
        <rusty@...tcorp.com.au>, <john.wanghui@...wei.com>,
        <wencongyang2@...wei.com>, <guijianfeng@...wei.com>
Subject: Re: [PATCH] modpost: abort if a module name is too long



On 2017/5/31 11:30, Jessica Yu wrote:
> +++ Wanlong Gao [31/05/17 10:23 +0800]:
>> Hi Jessica,
>>
>> On 2017/5/29 17:10, Jessica Yu wrote:
>>> +++ Xie XiuQi [20/05/17 15:46 +0800]:
>>>> From: Wanlong Gao <gaowanlong@...wei.com>
>>>>
>>>> Module name has a limited length, but currently the build system
>>>> allows the build finishing even if the module name is too long.
>>>>
>>>>  CC      /root/kprobe_example/abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz.mod.o
>>>> /root/kprobe_example/abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz.mod.c:9:2:
>>>> warning: initializer-string for array of chars is too long [enabled by default]
>>>>  .name = KBUILD_MODNAME,
>>>>  ^
>>>>
>>>> but it's merely a warning.
>>>>
>>>> This patch adds the check of the module name length in modpost and stops
>>>> the build properly.
>>>>
>>>> Signed-off-by: Wanlong Gao <gaowanlong@...wei.com>
>>>> Signed-off-by: Xie XiuQi <xiexiuqi@...wei.com>
>>>> ---
>>>> scripts/mod/modpost.c | 11 +++++++++++
>>>> 1 file changed, 11 insertions(+)
>>>>
>>>> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
>>>> index 30d752a..db11c57 100644
>>>> --- a/scripts/mod/modpost.c
>>>> +++ b/scripts/mod/modpost.c
>>>> @@ -2166,6 +2166,17 @@ static int add_versions(struct buffer *b, struct module *mod)
>>>> {
>>>>     struct symbol *s, *exp;
>>>>     int err = 0;
>>>> +    const char *mod_name;
>>>> +
>>>> +    mod_name = strrchr(mod->name, '/');
>>>> +    if (mod_name == NULL)
>>>> +        mod_name = mod->name;
>>>> +    else
>>>> +        mod_name++;
>>>> +    if (strlen(mod_name) >= MODULE_NAME_LEN) {
>>>> +        merror("module name is too long [%s.ko]\n", mod->name);
>>>> +        return 1;
>>>> +    }
>>>
>>> Hi Xie,
>>>
>>> This check shouldn't be in add_versions() (which does something else entirely),
>>> it should probably be put in a separate helper function called from main. But
>>> I'm not a big fan of the extra string manipulation to do something this simple.
>>>
>>> I think this check can be vastly simplified, how about something like the
>>> following?
>>
>> This looks better, would you apply your following patch?
>>
>> Reviewed-by: Wanlong Gao <gaowanlong@...wei.com>
>> Tested-by: Wanlong Gao <gaowanlong@...wei.com>
> 
> Sure, thanks for testing. I'll go ahead and format this into a proper
> patch and resend.

Please wait, I just found that this patch makes the built module can't
be inserted by the following error:

# insmod abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabc.ko 
insmod: ERROR: could not insert module abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabc.ko: Invalid parameters

# dmesg
abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabc: Unknown symbol __fentry__ (err -22)


Thanks,
Wanlong Gao

> 
> Jessica
> 
>>>
>>> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
>>> index 48397fe..bb09fc7 100644
>>> --- a/scripts/mod/modpost.c
>>> +++ b/scripts/mod/modpost.c
>>> @@ -2139,6 +2139,9 @@ static void add_header(struct buffer *b, struct module *mod)
>>>                   "#endif\n");
>>>     buf_printf(b, "\t.arch = MODULE_ARCH_INIT,\n");
>>>     buf_printf(b, "};\n");
>>> +    buf_printf(b, "\n");
>>> +    buf_printf(b, "static void __attribute__((section(\".discard\"), used)) __modname_test(void)\n");
>>> +    buf_printf(b, "{ BUILD_BUG_ON(sizeof(KBUILD_MODNAME) > MODULE_NAME_LEN); }\n");
>>> }
>>>
>>> static void add_intree_flag(struct buffer *b, int is_intree)
>>>
>>> This simply checks if KBUILD_MODNAME > MODULE_NAME_LEN and breaks the build if
>>> it does.
>>>
>>> Jessica
>>>
>>>>     for (s = mod->unres; s; s = s->next) {
>>>>         exp = find_symbol(s->name);
>>>> -- 
>>>> 1.8.3.1
>>>>
>>>
>>> .
>>>
>>
> 
> .
>