2022-06-08 12:53:34

by Harshit Mogalapalli

Subject: [PATCH] HID: cp2112: prevent a buffer overflow in cp2112_xfer()

Smatch warnings:
drivers/hid/hid-cp2112.c:793 cp2112_xfer() error: __memcpy()
'data->block[1]' too small (33 vs 255)
drivers/hid/hid-cp2112.c:793 cp2112_xfer() error: __memcpy() 'buf' too
small (64 vs 255)

The 'read_length' variable is provided by 'data->block[0]' which comes
from user and it(read_length) can take a value between 0-255. Add an
upper bound to 'read_length' variable to prevent a buffer overflow in
memcpy().

Fixes: 542134c0375b ("HID: cp2112: Fix I2C_BLOCK_DATA transactions")
Signed-off-by: Harshit Mogalapalli <[email protected]>
---
drivers/hid/hid-cp2112.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/drivers/hid/hid-cp2112.c b/drivers/hid/hid-cp2112.c
index ece147d1a278..1e16b0fa310d 100644
--- a/drivers/hid/hid-cp2112.c
+++ b/drivers/hid/hid-cp2112.c
@@ -790,6 +790,11 @@ static int cp2112_xfer(struct i2c_adapter *adap, u16 addr,
data->word = le16_to_cpup((__le16 *)buf);
break;
case I2C_SMBUS_I2C_BLOCK_DATA:
+ if (read_length > I2C_SMBUS_BLOCK_MAX) {
+ ret = -EINVAL;
+ goto power_normal;
+ }
+
memcpy(data->block + 1, buf, read_length);
break;
case I2C_SMBUS_BLOCK_DATA:
--
2.31.1

2022-06-09 09:17:01

by Jiri Kosina

Subject: Re: [PATCH] HID: cp2112: prevent a buffer overflow in cp2112_xfer()

On Wed, 8 Jun 2022, Harshit Mogalapalli wrote:

> Smatch warnings:
> drivers/hid/hid-cp2112.c:793 cp2112_xfer() error: __memcpy()
> 'data->block[1]' too small (33 vs 255)
> drivers/hid/hid-cp2112.c:793 cp2112_xfer() error: __memcpy() 'buf' too
> small (64 vs 255)
>
> The 'read_length' variable is provided by 'data->block[0]' which comes
> from user and it(read_length) can take a value between 0-255. Add an
> upper bound to 'read_length' variable to prevent a buffer overflow in
> memcpy().
>
> Fixes: 542134c0375b ("HID: cp2112: Fix I2C_BLOCK_DATA transactions")
> Signed-off-by: Harshit Mogalapalli <[email protected]>
> ---
> drivers/hid/hid-cp2112.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/hid/hid-cp2112.c b/drivers/hid/hid-cp2112.c
> index ece147d1a278..1e16b0fa310d 100644
> --- a/drivers/hid/hid-cp2112.c
> +++ b/drivers/hid/hid-cp2112.c
> @@ -790,6 +790,11 @@ static int cp2112_xfer(struct i2c_adapter *adap, u16 addr,
> data->word = le16_to_cpup((__le16 *)buf);
> break;
> case I2C_SMBUS_I2C_BLOCK_DATA:
> + if (read_length > I2C_SMBUS_BLOCK_MAX) {
> + ret = -EINVAL;
> + goto power_normal;
> + }
> +
> memcpy(data->block + 1, buf, read_length);
> break;

Good catch, now applied. Thanks,

--
Jiri Kosina
SUSE Labs