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

[Wanlong Gao]

Hi Jessica,

On 2017/5/29 17:10, Jessica Yu wrote:
> +++ Xie XiuQi [20/05/17 15:46 +0800]:
>> From: Wanlong Gao <gaowanlong@xxxxxxxxxx>
>>
>> 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@xxxxxxxxxx>
>> Signed-off-by: Xie XiuQi <xiexiuqi@xxxxxxxxxx>
>> ---
>> 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@xxxxxxxxxx>
Tested-by: Wanlong Gao <gaowanlong@xxxxxxxxxx>


Thanks,
Wanlong Gao

> 
> 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
>>
> 
> .
>