Re: [PATCH 2/2] ath11k: Handle errors if peer creation fails

Alex Dewar
2020-11-07T13:50:02Z

On Sat, Nov 07, 2020 at 01:23:30PM +0200, Kalle Valo wrote:
> Alex Dewar <alex.dewar90@gmail.com> writes:
>
> > On Tue, Oct 06, 2020 at 10:26:28AM +0300, Kalle Valo wrote:
> >> Alex Dewar <alex.dewar90@gmail.com> writes:
> >>
> >> > ath11k_peer_create() is called without its return value being checked,
> >> > meaning errors will be unhandled. Add missing check and, as the mutex is
> >> > unconditionally unlocked on leaving this function, simplify the exit
> >> > path.
> >> >
> >> > Addresses-Coverity-ID: 1497531 ("Code maintainability issues")
> >> > Fixes: 701e48a43e15 ("ath11k: add packet log support for QCA6390")
> >> > Signed-off-by: Alex Dewar <alex.dewar90@gmail.com>
> >> > ---
> >> > drivers/net/wireless/ath/ath11k/mac.c | 21 +++++++++------------
> >> > 1 file changed, 9 insertions(+), 12 deletions(-)
> >> >
> >> > diff --git a/drivers/net/wireless/ath/ath11k/mac.c b/drivers/net/wireless/ath/ath11k/mac.c
> >> > index 7f8dd47d2333..58db1b57b941 100644
> >> > --- a/drivers/net/wireless/ath/ath11k/mac.c
> >> > +++ b/drivers/net/wireless/ath/ath11k/mac.c
> >> > @@ -5211,7 +5211,7 @@ ath11k_mac_op_assign_vif_chanctx(struct ieee80211_hw *hw,
> >> > struct ath11k *ar = hw->priv;
> >> > struct ath11k_base *ab = ar->ab;
> >> > struct ath11k_vif *arvif = (void *)vif->drv_priv;
> >> > - int ret;
> >> > + int ret = 0;
> >>
> >> I prefer not to initialise the ret variable.
> >>
> >> > arvif->is_started = true;
> >> >
> >> > /* TODO: Setup ps and cts/rts protection */
> >> >
> >> > - mutex_unlock(&ar->conf_mutex);
> >> > -
> >> > - return 0;
> >> > -
> >> > -err:
> >> > +unlock:
> >> > mutex_unlock(&ar->conf_mutex);
> >> >
> >> > return ret;
> >>
> >> So in the pending branch I changed this to:
> >>
> >> ret = 0;
> >>
> >> out:
> >> mutex_unlock(&ar->conf_mutex);
> >>
> >> return ret;
> >>
> >> Please check.
> >
> > I'm afraid you've introduced a bug ;). The body of the first if-statement
> > in the function doesn't set ret because no error has occurred. So now
> > it'll jump to the label and the function will return ret uninitialized.
>
> Ouch, so I did. Good catch! I would have hoped that GCC warns about that
> but it didn't.
>
> I fixed the bug and added also a warning messages if peer_create()
> fails:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/kvalo/ath.git/commit/?h=pending&id=e3e7b8072fa6bb0928b9066cf76e19e6bd2ec663
>
> Does this look better now? :)

LGTM!

>
> > With the gcc extension, ret will be initialised to zero anyway, so we're
> > not saving anything by explicitly assigning to ret later in the
> > function.
>
> I prefer not to initialise ret in the beginning of the function and I
> try to maintain that style in ath11k. I think it's more readable that
> the error value is assigned just before the goto.

Fair enough. I appreciate that it's a style issue.

>
> --
> https://patchwork.kernel.org/project/linux-wireless/list/
>
> https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches