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Date:   Mon, 6 May 2019 08:43:57 +0200
From:   Stanislaw Gruszka <sgruszka@redhat.com>
To:     Tony Chuang <yhchuang@realtek.com>
Cc:     "linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>
Subject: Re: [PATCH 5.1] rtw88: fix subscript above array bounds compiler
 warning
Message-ID: <20190506064357.GB5115@redhat.com>
References: <20190506062358.8288-1-sgruszka@redhat.com>
 <F7CD281DE3E379468C6D07993EA72F84D17EB2B5@RTITMBSVM04.realtek.com.tw>
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On Mon, May 06, 2019 at 06:32:01AM +0000, Tony Chuang wrote:
> > Subject: [PATCH 5.1] rtw88: fix subscript above array bounds compiler warning
> > 
> > My compiler complains about:
> > 
> > drivers/net/wireless/realtek/rtw88/phy.c: In function
> > ‘rtw_phy_rf_power_2_rssi’:
> > drivers/net/wireless/realtek/rtw88/phy.c:430:26: warning: array subscript is
> > above array bounds [-Warray-bounds]
> >   linear = db_invert_table[i][j];
> > 
> > According to comment power_db should be in range 1 ~ 96 .
> > To fix add check for boundaries before access the array.
> > 
> > Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
> > ---
> > RFC -> v1
> > - add check before accessing the array insted of
> >   rtw_phy_power_2_db() change.
> > 
> >  drivers/net/wireless/realtek/rtw88/phy.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> > 
> > diff --git a/drivers/net/wireless/realtek/rtw88/phy.c
> > b/drivers/net/wireless/realtek/rtw88/phy.c
> > index 4381b360b5b5..9ca52a4d025a 100644
> > --- a/drivers/net/wireless/realtek/rtw88/phy.c
> > +++ b/drivers/net/wireless/realtek/rtw88/phy.c
> > @@ -423,6 +423,11 @@ static u64 rtw_phy_db_2_linear(u8 power_db)
> >  	u8 i, j;
> >  	u64 linear;
> > 
> > +	if (power_db > 96)
> > +		power_db = 96;
> > +	else if (power_db < 1)
> > +		power_db = 1;
> 
> I think it's "return 1" here.

Ehh, I missed that in your comment. However 'return 1' change
the output of rtw_phy_db_2_linear() quite substantially
as the smallest value (for power_db = 1) from db_invert_table[][]
is 10. I'll post v2 patch, but please double check it's indeed
correct logic. Thanks.

Stanislaw