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Subject: Re: [PATCH v2] media: si2165: fix a missing check of return value
To:     Sean Young <sean@mess.org>
Cc:     Kangjie Lu <kjlu@umn.edu>, pakki001@umn.edu,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        linux-media@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20181221045403.59303-1-kjlu@umn.edu>
 <7a5d505d-692b-f067-51f6-815787cffba3@gentoo.org>
 <20190305211743.vi6zksuw2eltusif@gofer.mess.org>
From:   Matthias Schwarzott <zzam@gentoo.org>
Message-ID: <a6c6075d-27fd-4e07-2d9c-28186e75aab8@gentoo.org>
Date:   Wed, 6 Mar 2019 22:36:58 +0100
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Am 05.03.19 um 22:17 schrieb Sean Young:
> 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@umn.edu>
>>
>> Reviewed-by: Matthias Schwarzott <zzam@gentoo.org>
> 
> Unless it is tested on the actual hardware we can't apply this. This could
> introduce regressions.
> 

I tested it on a Hauppauge WinTV-HVR5500 tuning to DVB-C.

Regards
Matthias

Tested-by: Matthias Schwarzott <zzam@gentoo.org>

> 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,
>>>
>