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

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Message-ID: <23f3b0e2-dcc6-2165-68d6-a88fac1ba9ff@huawei.com>
Date:   Thu, 1 Jun 2017 19:51:17 +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

Jessica,

On 2017/5/31 11:48, Wanlong Gao wrote:
> 
> 
> 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)
> 
> 

Any idea about this error?

Thanks,
Wanlong Gao

> 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
>>>>>
>>>>
>>>> .
>>>>
>>>
>>
>> .
>>
> 
> 
> .
>