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

[Jessica Yu]

+++ 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@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>

Sure, thanks for testing. I'll go ahead and format this into a proper
patch and resend.

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
> >
> > .