linux-kernel - Re: [PATCH v2] media: si2165: fix a missing check of return value

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Message-ID: <20190305211743.vi6zksuw2eltusif@gofer.mess.org>
Date:   Tue, 5 Mar 2019 21:17:43 +0000
From:   Sean Young <sean@...s.org>
To:     Matthias Schwarzott <zzam@...too.org>
Cc:     Kangjie Lu <kjlu@....edu>, pakki001@....edu,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] media: si2165: fix a missing check of return value

On Fri, Dec 21, 2018 at 09:24:46AM +0100, Matthias Schwarzott wrote:
> Am 21.12.18 um 05:54 schrieb Kangjie Lu:
> > si2165_readreg8() may fail. Looking into si2165_readreg8(), we will find
> > that "val_tmp" will be an uninitialized value when regmap_read() fails.
> > "val_tmp" is then assigned to "val". So if si2165_readreg8() fails,
> > "val" will be a random value. Further use will lead to undefined
> > behaviors. The fix checks if si2165_readreg8() fails, and if so, returns
> > its error code upstream.
> > 
> > Signed-off-by: Kangjie Lu <kjlu@....edu>
> 
> Reviewed-by: Matthias Schwarzott <zzam@...too.org>

Unless it is tested on the actual hardware we can't apply this. This could
introduce regressions.

Sean

> 
> > ---
> >  drivers/media/dvb-frontends/si2165.c | 8 +++++---
> >  1 file changed, 5 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/media/dvb-frontends/si2165.c b/drivers/media/dvb-frontends/si2165.c
> > index feacd8da421d..d55d8f169dca 100644
> > --- a/drivers/media/dvb-frontends/si2165.c
> > +++ b/drivers/media/dvb-frontends/si2165.c
> > @@ -275,18 +275,20 @@ static u32 si2165_get_fe_clk(struct si2165_state *state)
> >  
> >  static int si2165_wait_init_done(struct si2165_state *state)
> >  {
> > -	int ret = -EINVAL;
> > +	int ret;
> >  	u8 val = 0;
> >  	int i;
> >  
> >  	for (i = 0; i < 3; ++i) {
> > -		si2165_readreg8(state, REG_INIT_DONE, &val);
> > +		ret = si2165_readreg8(state, REG_INIT_DONE, &val);
> > +		if (ret < 0)
> > +			return ret;
> >  		if (val == 0x01)
> >  			return 0;
> >  		usleep_range(1000, 50000);
> >  	}
> >  	dev_err(&state->client->dev, "init_done was not set\n");
> > -	return ret;
> > +	return -EINVAL;
> >  }
> >  
> >  static int si2165_upload_firmware_block(struct si2165_state *state,
> >