Re: [PATCH 05/24] media: dvb-usb-v2: ec168: fix null-ptr-deref in ec168_i2c_xfer()

[Wei Chen]

Dear Linux Developers,

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?

Thanks,
Wei


------ Original Message ------
> From zzam@xxxxxxxxxx
To "Mauro Carvalho Chehab" <mchehab@xxxxxxxxxx>
Cc "Wei Chen" <harperchen1110@xxxxxxxxx>; "Antti Palosaari" <crope@xxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; linux-media@xxxxxxxxxxxxxxx
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@xxxxxxxxx>
> >
> > 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@xxxxxxxxx
> > Signed-off-by: Wei Chen <harperchen1110@xxxxxxxxx>
> > Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
> > ---
> >   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 */