linux-kernel - Re: Build regressions/improvements in v6.4 (wireless/airo)

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Message-ID: <CAMuHMdU30BzfzQ=xEDFCd2bXG=VD68sQz-60Ok8GethLsnEH8A@mail.gmail.com>
Date:   Sun, 9 Jul 2023 10:27:54 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     linux-kernel@...r.kernel.org, Kalle Valo <kvalo@...nel.org>,
        linux-wireless@...r.kernel.org,
        John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
Subject: Re: Build regressions/improvements in v6.4 (wireless/airo)

Hi Randy,

On Sun, Jul 9, 2023 at 4:46 AM Randy Dunlap <rdunlap@...radead.org> wrote:
> On 6/26/23 01:24, Geert Uytterhoeven wrote:
> > On Mon, 26 Jun 2023, Geert Uytterhoeven wrote:
> >> JFYI, when comparing v6.4[1] to v6.4-rc7[3], the summaries are:
> >>  - build errors: +1/-0
> >
> >   + /kisskb/src/drivers/net/wireless/cisco/airo.c: error: 'status_rid.currentXmitRate' is used uninitialized [-Werror=uninitialized]:  => 6163:45
>
> I cannot reproduce this build error. (I don't doubt the problem, just having a problem
> making it happen for me.)
> I have tried it with gcc-11.1.0, gcc-11.3.0, and gcc-13.1.0.

Which is similar to kisskb, using sh4-linux-gcc (GCC) 11.3.0...

> I'm surprised that this is the only instance that gcc found/warned about.

Indeed.

>
> I have a patch for this one instance, but there are 40+ instances of
>         readStatusRid()
>         readConfigRid()
>         readSsidRid()
>         readStatsRid()
>         readCapabilityRid()
> that don't check the return status of the function calls.
>
> I suppose that a patch can quieten the compiler error/warning, but given
> the 40+ other problems, it won't make the driver any noticeably better IMO.

Indeed...

> > sh4-gcc11/sh-allmodconfig
> > seen before
> >
> > This is actually a real issue, and it's been here since basically forever.
> >
> > drivers/net/wireless/cisco/airo.c:
> >
> >     static int airo_get_rate(struct net_device *dev,
> >                              struct iw_request_info *info,
> >                              union iwreq_data *wrqu,
> >                              char *extra)
> >     {
> >             struct iw_param *vwrq = &wrqu->bitrate;
> >             struct airo_info *local = dev->ml_priv;
> >             StatusRid status_rid;           /* Card status info */
> >
> >             readStatusRid(local, &status_rid, 1);
> >
> > ==>         vwrq->value = le16_to_cpu(status_rid.currentXmitRate) * 500000;
> >             ...
> >     }
> >
> >     static int readStatusRid(struct airo_info *ai, StatusRid *statr, int lock)
> >     {
> >             return PC4500_readrid(ai, RID_STATUS, statr, sizeof(*statr), lock);
> >     }
> >
> >     static int PC4500_readrid(struct airo_info *ai, u16 rid, void *pBuf, int len, int lock)
> >     {
> >             u16 status;
> >             int rc = SUCCESS;
> >
> >             if (lock) {
> >                     if (down_interruptible(&ai->sem))
> >                             return ERROR;
> >
> > pBuf output buffer contents not initialized.
> >
> >             }
> >             ...
> >     }
> >
> >
> >> [1] http://kisskb.ellerman.id.au/kisskb/branch/linus/head/6995e2de6891c724bfeb2db33d7b87775f913ad1/ (all 160 configs)
> >> [3] http://kisskb.ellerman.id.au/kisskb/branch/linus/head/45a3e24f65e90a047bef86f927ebdc4c710edaa1/ (all 160 configs)
>
> I appreciate the synopsis.  Here's a patch.  WDYT?
> ---
> From: Randy Dunlap <rdunlap@...radead.org>
> Subject: [PATCH] wifi: airo: avoid uninitialized warning in airo_get_rate()
>
> Quieten a gcc (11.3.0) build error or warning by checking the function
> call status and returning -EIO if the function call failed.
> This is similar to what several other wireless drivers do for the
> SIOCGIWRATE ioctl call.
>
> drivers/net/wireless/cisco/airo.c: error: 'status_rid.currentXmitRate' is used uninitialized [-Werror=uninitialized]
>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Randy Dunlap <rdunlap@...radead.org>
> Reported-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> Link: lore.kernel.org/r/39abf2c7-24a-f167-91da-ed4c5435d1c4@...ux-m68k.org
> Cc: Kalle Valo <kvalo@...nel.org>
> Cc: linux-wireless@...r.kernel.org
> ---
>  drivers/net/wireless/cisco/airo.c |    5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff -- a/drivers/net/wireless/cisco/airo.c b/drivers/net/wireless/cisco/airo.c
> --- a/drivers/net/wireless/cisco/airo.c
> +++ b/drivers/net/wireless/cisco/airo.c
> @@ -6157,8 +6157,11 @@ static int airo_get_rate(struct net_devi
>         struct iw_param *vwrq = &wrqu->bitrate;
>         struct airo_info *local = dev->ml_priv;
>         StatusRid status_rid;           /* Card status info */
> +       int ret;
>
> -       readStatusRid(local, &status_rid, 1);
> +       ret = readStatusRid(local, &status_rid, 1);
> +       if (ret)
> +               return -EIO;

That's about the best we can do without further surgery.
E.g. PC4500_readrid() should return a proper error code instead of
just ERROR/SUCCESS.
The case gcc complains about is when lock = 1 and the call to
down_interruptible() fails, for which -EBUSY would be appropriate.

>
>         vwrq->value = le16_to_cpu(status_rid.currentXmitRate) * 500000;
>         /* If more than one rate, set auto */
>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds