Re: [PATCH] modinfo: don't parse built-in for explicitly given module files

[Lucas De Marchi <lucas.de.marchi@gmail.com>]

On Wed, Aug 18, 2021 at 4:23 AM Takashi Iwai <tiwai@suse.de> wrote:
>
> A recent bug report showed that modinfo doesn't give the signature
> information for certain modules, and it turned out to happen only on
> the modules that are built-in on the running kernel; then modinfo
> skips the signature check, as if the target module file never exists.
> The behavior is, however, inconsistent when modinfo is performed for
> external modules (no matter which kernel version is) and the module
> file path is explicitly given by a command-line argument, which
> guarantees the presence of the module file itself.
>
> This patch addresses the regression by checking the presence of the
> module path at first before checking the built-in module.
>
> Fixes: e7e2cb61fa9f ("modinfo: Show information about built-in modules")
> BugLink: https://bugzilla.opensuse.org/show_bug.cgi?id=1189537
> Signed-off-by: Takashi Iwai <tiwai@suse.de>
> ---
>  libkmod/libkmod-module.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/libkmod/libkmod-module.c b/libkmod/libkmod-module.c
> index 6e0ff1a99604..9e878a5345a1 100644
> --- a/libkmod/libkmod-module.c
> +++ b/libkmod/libkmod-module.c
> @@ -2292,7 +2292,8 @@ KMOD_EXPORT int kmod_module_get_info(const struct kmod_module *mod, struct kmod_
>         assert(*list == NULL);
>
>         /* remove const: this can only change internal state */
> -       if (kmod_module_is_builtin((struct kmod_module *)mod)) {
> +       if (!kmod_module_get_path(mod) &&
> +           kmod_module_is_builtin((struct kmod_module *)mod)) {

thanks for spotting this... but I'm not sure this is the right fix.
kmod_module_is_builtin() shouldn't return true if the module was
created by path rather than lookup. It seems we should rather set
mod->builtin = KMOD_MODULE_BUILTIN_NO in
kmod_module_new_from_path(). This would also fix the use of
kmod_module_is_builtin() directly by applications.

Since the builtin check uses lazy initialization,  the default is
KMOD_MODULE_BUILTIN_UNKNOWN, hence the bug here.

Lucas De Marchi

>                 count = kmod_builtin_get_modinfo(mod->ctx,
>                                                 kmod_module_get_name(mod),
>                                                 &strings);
> --
> 2.26.2
>