linux-hardening - RE: [PATCH 063/141] HID: input: Fix fall-through warnings for Clang

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Date:   Wed, 25 Nov 2020 13:34:53 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Jiri Kosina' <jikos@...nel.org>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>
CC:     Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        "linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hardening@...r.kernel.org" <linux-hardening@...r.kernel.org>
Subject: RE: [PATCH 063/141] HID: input: Fix fall-through warnings for Clang

From: Jiri Kosina <jikos@...nel.org>
> Sent: 25 November 2020 13:04
> On Fri, 20 Nov 2020, Gustavo A. R. Silva wrote:
> 
> > In preparation to enable -Wimplicit-fallthrough for Clang, fix a warning
> > by explicitly adding a goto statement instead of letting the code fall
> > through to the next case.
> >
> > Link: https://github.com/KSPP/linux/issues/115
> > Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> > ---
> >  drivers/hid/hid-input.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
> > index 9770db624bfa..37601b800a2e 100644
> > --- a/drivers/hid/hid-input.c
> > +++ b/drivers/hid/hid-input.c
> > @@ -743,6 +743,7 @@ static void hidinput_configure_usage(struct hid_input *hidinput, struct hid_fiel
> >  				field->flags |= HID_MAIN_ITEM_RELATIVE;
> >  				break;
> >  			}
> > +			goto unknown;
> >
> >  		default: goto unknown;
> 
> This makes my eyes hurt :) But adding the annotation would be ugly as
> well, so let me just take it as-is.

                case HID_GD_RFKILL_BTN:
                        /* MS wireless radio ctl extension, also check CA */
                        if (field->application == HID_GD_WIRELESS_RADIO_CTLS) {
                                map_key_clear(KEY_RFKILL);
                                /* We need to simulate the btn release */
                                field->flags |= HID_MAIN_ITEM_RELATIVE;
                                break;
                        }

It might be best to invert the condition and de-indent the code.
                case HID_GD_RFKILL_BTN:
                        /* MS wireless radio ctl extension, also check CA */
                        if (field->application != HID_GD_WIRELESS_RADIO_CTLS)
                                goto unknown;
                        map_key_clear(KEY_RFKILL);
                        /* We need to simulate the btn release */
                        field->flags |= HID_MAIN_ITEM_RELATIVE;
                        break;

	David

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