2023-05-13 18:11:46

by Mauro Carvalho Chehab

Subject: [PATCH 07/24] media: dvb-usb-v2: rtl28xxu: fix null-ptr-deref in rtl28xxu_i2c_xfer

From: Zhang Shurong <[email protected]>

In rtl28xxu_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. Malicious data finally reach rtl28xxu_i2c_xfer. If accessing
msg[i].buf[0] without sanity check, null ptr 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()")

Link: https://lore.kernel.org/linux-media/[email protected]
Signed-off-by: Zhang Shurong <[email protected]>
Signed-off-by: Mauro Carvalho Chehab <[email protected]>
---
drivers/media/usb/dvb-usb-v2/rtl28xxu.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)

diff --git a/drivers/media/usb/dvb-usb-v2/rtl28xxu.c b/drivers/media/usb/dvb-usb-v2/rtl28xxu.c
index 795a012d4020..f7884bb56fcc 100644
--- a/drivers/media/usb/dvb-usb-v2/rtl28xxu.c
+++ b/drivers/media/usb/dvb-usb-v2/rtl28xxu.c
@@ -176,6 +176,10 @@ static int rtl28xxu_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msg[],
ret = -EOPNOTSUPP;
goto err_mutex_unlock;
} else if (msg[0].addr == 0x10) {
+ if (msg[0].len < 1 || msg[1].len < 1) {
+ ret = -EOPNOTSUPP;
+ goto err_mutex_unlock;
+ }
/* method 1 - integrated demod */
if (msg[0].buf[0] == 0x00) {
/* return demod page from driver cache */
@@ -189,6 +193,10 @@ static int rtl28xxu_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msg[],
ret = rtl28xxu_ctrl_msg(d, &req);
}
} else if (msg[0].len < 2) {
+ if (msg[0].len < 1) {
+ ret = -EOPNOTSUPP;
+ goto err_mutex_unlock;
+ }
/* method 2 - old I2C */
req.value = (msg[0].buf[0] << 8) | (msg[0].addr << 1);
req.index = CMD_I2C_RD;
@@ -217,8 +225,16 @@ static int rtl28xxu_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msg[],
ret = -EOPNOTSUPP;
goto err_mutex_unlock;
} else if (msg[0].addr == 0x10) {
+ if (msg[0].len < 1) {
+ ret = -EOPNOTSUPP;
+ goto err_mutex_unlock;
+ }
/* method 1 - integrated demod */
if (msg[0].buf[0] == 0x00) {
+ if (msg[0].len < 2) {
+ ret = -EOPNOTSUPP;
+ goto err_mutex_unlock;
+ }
/* save demod page for later demod access */
dev->page = msg[0].buf[1];
ret = 0;
@@ -231,6 +247,10 @@ static int rtl28xxu_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msg[],
ret = rtl28xxu_ctrl_msg(d, &req);
}
} else if ((msg[0].len < 23) && (!dev->new_i2c_write)) {
+ if (msg[0].len < 1) {
+ ret = -EOPNOTSUPP;
+ goto err_mutex_unlock;
+ }
/* method 2 - old I2C */
req.value = (msg[0].buf[0] << 8) | (msg[0].addr << 1);
req.index = CMD_I2C_WR;
--
2.40.1

2023-05-17 07:01:34

by Matthias Schwarzott

Subject: Re: [PATCH 07/24] media: dvb-usb-v2: rtl28xxu: fix null-ptr-deref in rtl28xxu_i2c_xfer

Am 13.05.23 um 19:57 schrieb Mauro Carvalho Chehab:
> From: Zhang Shurong <[email protected]>
>
> In rtl28xxu_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. Malicious data finally reach rtl28xxu_i2c_xfer. If accessing
> msg[i].buf[0] without sanity check, null ptr 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()")
>
> Link: https://lore.kernel.org/linux-media/[email protected]
> Signed-off-by: Zhang Shurong <[email protected]>
> Signed-off-by: Mauro Carvalho Chehab <[email protected]>
> ---
> drivers/media/usb/dvb-usb-v2/rtl28xxu.c | 20 ++++++++++++++++++++
> 1 file changed, 20 insertions(+)
>
> diff --git a/drivers/media/usb/dvb-usb-v2/rtl28xxu.c b/drivers/media/usb/dvb-usb-v2/rtl28xxu.c
> index 795a012d4020..f7884bb56fcc 100644
> --- a/drivers/media/usb/dvb-usb-v2/rtl28xxu.c
> +++ b/drivers/media/usb/dvb-usb-v2/rtl28xxu.c
> @@ -176,6 +176,10 @@ static int rtl28xxu_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msg[],
> ret = -EOPNOTSUPP;
> goto err_mutex_unlock;
> } else if (msg[0].addr == 0x10) {

Is there a need to compare msg[0].addr and msg[1].addr for the combined
write+read transfer?

@Mauro: It seems a lot of i2c_xfer functions do only partial checking of
address and direction for these combined write+read transfers. Is this a
problem?

> + if (msg[0].len < 1 || msg[1].len < 1) {
> + ret = -EOPNOTSUPP;
> + goto err_mutex_unlock;
> + }
> /* method 1 - integrated demod */
> if (msg[0].buf[0] == 0x00) {
> /* return demod page from driver cache */
> @@ -189,6 +193,10 @@ static int rtl28xxu_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msg[],
> ret = rtl28xxu_ctrl_msg(d, &req);
> }
> } else if (msg[0].len < 2) {
> + if (msg[0].len < 1) {
The code sequence is correct, but looks a bit strange. Maybe this is better:
} else if (msg[0].len < 1) {
ret = -EOPNOTSUPP;
goto err_mutex_unlock;
} else if (msg[0].len < 2) {

> + ret = -EOPNOTSUPP;
> + goto err_mutex_unlock;
> + }
> /* method 2 - old I2C */
> req.value = (msg[0].buf[0] << 8) | (msg[0].addr << 1);
> req.index = CMD_I2C_RD;
> @@ -217,8 +225,16 @@ static int rtl28xxu_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msg[],
> ret = -EOPNOTSUPP;
> goto err_mutex_unlock;
> } else if (msg[0].addr == 0x10) {
> + if (msg[0].len < 1) {
Is a write of a single byte fine? req.size below will be 0.

> + ret = -EOPNOTSUPP;
> + goto err_mutex_unlock;
> + }
> /* method 1 - integrated demod */
> if (msg[0].buf[0] == 0x00) {
> + if (msg[0].len < 2) {
> + ret = -EOPNOTSUPP;
> + goto err_mutex_unlock;
> + }
> /* save demod page for later demod access */
> dev->page = msg[0].buf[1];
> ret = 0;
> @@ -231,6 +247,10 @@ static int rtl28xxu_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msg[],
> ret = rtl28xxu_ctrl_msg(d, &req);
> }
> } else if ((msg[0].len < 23) && (!dev->new_i2c_write)) {
> + if (msg[0].len < 1) {
> + ret = -EOPNOTSUPP;
> + goto err_mutex_unlock;
> + }
> /* method 2 - old I2C */
> req.value = (msg[0].buf[0] << 8) | (msg[0].addr << 1);
> req.index = CMD_I2C_WR;