On Wed, 5 Dec 2012 15:02:56 +0100, Benjamin Tissoires wrote: > The previous memcpy implementation relied on the size advertized by the > device. There were no guarantees that buf was big enough. > > Some gymnastic is also required with the +2/-2 to take into account > the first 2 bytes of the returned buffer where the total returned > length is supplied by the device. > > Signed-off-by: Benjamin Tissoires <[email protected]> > --- > drivers/hid/i2c-hid/i2c-hid.c | 16 ++++++++++++---- > 1 file changed, 12 insertions(+), 4 deletions(-) > > diff --git a/drivers/hid/i2c-hid/i2c-hid.c b/drivers/hid/i2c-hid/i2c-hid.c > index c6630d4..ce01d59 100644 > --- a/drivers/hid/i2c-hid/i2c-hid.c > +++ b/drivers/hid/i2c-hid/i2c-hid.c > @@ -502,23 +502,31 @@ static int i2c_hid_get_raw_report(struct hid_device > *hid, > { > struct i2c_client *client = hid->driver_data; > struct i2c_hid *ihid = i2c_get_clientdata(client); > + size_t ret_count, ask_count; > int ret; > > if (report_type == HID_OUTPUT_REPORT) > return -EINVAL; > > - if (count > ihid->bufsize) > - count = ihid->bufsize; > + /* +2 bytes to include the size of the reply in the query buffer */ > + ask_count = min(count + 2, (size_t)ihid->bufsize); > > ret = i2c_hid_get_report(client, > report_type == HID_FEATURE_REPORT ? 0x03 : 0x01, > - report_number, ihid->inbuf, count); > + report_number, ihid->inbuf, ask_count); > > if (ret < 0) > return ret; > > - count = ihid->inbuf[0] | (ihid->inbuf[1] << 8); > + ret_count = ihid->inbuf[0] | (ihid->inbuf[1] << 8); > > + if (!ret_count)
I'd make this (ret_count <= 2), as this would let you call memcpy with a null or even negative length. Other than that, the new code looks OK and safe. > + return 0; > + > + ret_count = min(ret_count, ask_count); > + > + /* The query buffer contains the size, dropping it in the reply */ > + count = min(count, ret_count - 2); > memcpy(buf, ihid->inbuf + 2, count); > > return count; -- Jean Delvare -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
