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

[Jessica Yu]

+++ 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?

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