netdev - Re: [PATCH ethtool-next] Fixing boolean value output for Netlink reported values in JSON format

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Date:   Mon, 9 Jan 2023 09:08:00 +0100
From:   Simon Horman <simon.horman@...igine.com>
To:     Max Georgiev <glipus@...il.com>
Cc:     mkubecek@...e.cz, netdev@...r.kernel.org, kuba@...nel.org
Subject: Re: [PATCH ethtool-next] Fixing boolean value output for Netlink
 reported values in JSON format

On Fri, Jan 06, 2023 at 03:16:30PM -0700, Max Georgiev wrote:
> On Thu, Jan 5, 2023 at 5:11 AM Simon Horman <simon.horman@...igine.com> wrote:
> >
> > On Tue, Dec 27, 2022 at 10:36:20AM -0700, Maxim Georgiev wrote:
> > > Current implementation of show_bool_val() passes "val" parameter of pointer
> > > type as a last parameter to print_bool():
> > > https://git.kernel.org/pub/scm/network/ethtool/ethtool.git/tree/netlink/netlink.h#n131
> > > ...
> > > static inline void show_bool_val(const char *key, const char *fmt, uint8_t *val)
> > > {
> > >       if (is_json_context()) {
> > >               if (val)
> > > >                     print_bool(PRINT_JSON, key, NULL, val);
> > >       } else {
> > > ...
> > > print_bool() expects the last parameter to be bool:
> > > https://git.kernel.org/pub/scm/network/ethtool/ethtool.git/tree/json_print.c#n153
> > > ...
> > > void print_bool(enum output_type type,
> > >               const char *key,
> > >               const char *fmt,
> > >               bool value)
> > > {
> > > ...
> > > Current show_bool_val() implementation converts "val" pointer to bool while
> > > calling show_bool_val(). As a result show_bool_val() always prints the value
> > > as "true" as long as it gets a non-null pointer to the boolean value, even if
> > > the referred boolean value is false.
> > >
> > > Fixes: 7e5c1ddbe67d ("pause: add --json support")
> > > Signed-off-by: Maxim Georgiev <glipus@...il.com>
> >
> > Reviewed-by: Simon Horman <simon.horman@...igine.com>
> >
> > I'm assuming that val is never NULL :)
> 
> Simon, thank you for taking a look!
> Yes, the "if (val)" check on line 130 guarantees that "print_bool()"
> on line 131 is called only if val is not null.

Thanks, that is pretty obvious now you point it out.
Looks good to me :)

> > > ---
> > >  netlink/netlink.h | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/netlink/netlink.h b/netlink/netlink.h
> > > index 3240fca..1274a3b 100644
> > > --- a/netlink/netlink.h
> > > +++ b/netlink/netlink.h
> > > @@ -128,7 +128,7 @@ static inline void show_bool_val(const char *key, const char *fmt, uint8_t *val)
> > >  {
> > >       if (is_json_context()) {
> > >               if (val)
> > > -                     print_bool(PRINT_JSON, key, NULL, val);
> > > +                     print_bool(PRINT_JSON, key, NULL, *val);
> > >       } else {
> > >               print_string(PRINT_FP, NULL, fmt, u8_to_bool(val));
> > >       }
> > > --
> > > 2.38.1
> > >