linux-kernel - Re: [PATCH 05/24] media: dvb-usb-v2: ec168: fix null-ptr-deref in ec168_i2c

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Message-ID: <c5e51a20-9fa4-3fa9-ee14-3410778e4dcf@gentoo.org>
Date:   Fri, 2 Jun 2023 08:41:47 +0200
From:   zzam@...too.org
To:     Wei Chen <harperchen1110@...il.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     Antti Palosaari <crope@....fi>, linux-kernel@...r.kernel.org,
        linux-media@...r.kernel.org
Subject: Re: [PATCH 05/24] media: dvb-usb-v2: ec168: fix null-ptr-deref in
 ec168_i2c_xfer()

Am 19.05.23 um 11:17 schrieb Wei Chen:
> Dear Linux Developers,
> 
Hi Wei,
> Thank you for the review for my patch in driver az6027 and ec168.
> 
> Yes, I agree with you. Sorry for my mistake. Since these two patches has 
> already been accepted and merged in git tree media, should I send a new 
> patch to revise this problem? Or how could I revise an accepted patch?

I think the best is to send new patches on top of the already accepted 
patches.

Regards
Matthias


> 
> Thanks,
> Wei
> 
> 
> ------ Original Message ------
>> From zzam@...too.org
> To "Mauro Carvalho Chehab" <mchehab@...nel.org>
> Cc "Wei Chen" <harperchen1110@...il.com>; "Antti Palosaari" 
> <crope@....fi>; linux-kernel@...r.kernel.org; linux-media@...r.kernel.org
> Date 2023/5/17 13:10:34
> Subject Re: [PATCH 05/24] media: dvb-usb-v2: ec168: fix null-ptr-deref 
> in ec168_i2c_xfer()
> 
>> Am 13.05.23 um 19:57 schrieb Mauro Carvalho Chehab:
>>> From: Wei Chen <harperchen1110@...il.com>
>>>
>>> In ec168_i2c_xfer, msg is controlled by user. When msg[i].buf is null
>>> and msg[i].len is zero, former checks on msg[i].buf would be passed.
>>> If accessing msg[i].buf[0] without sanity check, null pointer deref
>>> would happen. We add check on msg[i].len to prevent crash.
>>>
>>> Similar commit:
>>> commit 0ed554fd769a ("media: dvb-usb: az6027: fix null-ptr-deref in 
>>> az6027_i2c_xfer()")
>>>
>> Review comment below.
>>
>>> Link: 
>>> https://lore.kernel.org/linux-media/20230313085853.3252349-1-harperchen1110@gmail.com
>>> Signed-off-by: Wei Chen <harperchen1110@...il.com>
>>> Signed-off-by: Mauro Carvalho Chehab <mchehab@...nel.org>
>>> ---
>>>   drivers/media/usb/dvb-usb-v2/ec168.c | 12 ++++++++++++
>>>   1 file changed, 12 insertions(+)
>>>
>>> diff --git a/drivers/media/usb/dvb-usb-v2/ec168.c 
>>> b/drivers/media/usb/dvb-usb-v2/ec168.c
>>> index 7ed0ab9e429b..0e4773fc025c 100644
>>> --- a/drivers/media/usb/dvb-usb-v2/ec168.c
>>> +++ b/drivers/media/usb/dvb-usb-v2/ec168.c
>>> @@ -115,6 +115,10 @@ static int ec168_i2c_xfer(struct i2c_adapter 
>>> *adap, struct i2c_msg msg[],
>>>       while (i < num) {
>>>           if (num > i + 1 && (msg[i+1].flags & I2C_M_RD)) {
>>>               if (msg[i].addr == ec168_ec100_config.demod_address) {
>>> +                if (msg[i].len < 1) {
>>> +                    i = -EOPNOTSUPP;
>>> +                    break;
>>> +                }
>>>                   req.cmd = READ_DEMOD;
>>>                   req.value = 0;
>>>                   req.index = 0xff00 + msg[i].buf[0]; /* reg */
>>> @@ -131,6 +135,10 @@ static int ec168_i2c_xfer(struct i2c_adapter 
>>> *adap, struct i2c_msg msg[],
>>>               }
>>>           } else {
>>>               if (msg[i].addr == ec168_ec100_config.demod_address) {
>>> +                if (msg[i].len < 1) {
>>> +                    i = -EOPNOTSUPP;
>>> +                    break;
>>> +                }
>> The check condition should be msg[i].len < 2 or != 2. The following 
>> lines access msg[i].buf elements 0 and 1.
>>>                   req.cmd = WRITE_DEMOD;
>>>                   req.value = msg[i].buf[1]; /* val */
>>>                   req.index = 0xff00 + msg[i].buf[0]; /* reg */
>>> @@ -139,6 +147,10 @@ static int ec168_i2c_xfer(struct i2c_adapter 
>>> *adap, struct i2c_msg msg[],
>>>                   ret = ec168_ctrl_msg(d, &req);
>>>                   i += 1;
>>>               } else {
>>> +                if (msg[i].len < 1) {
>>> +                    i = -EOPNOTSUPP;
>>> +                    break;
>>> +                }
>>>                   req.cmd = WRITE_I2C;
>>>                   req.value = msg[i].buf[0]; /* val */
>>>                   req.index = 0x0100 + msg[i].addr; /* I2C addr */
>>