Moikka Dan,
and thank you. Comments below.
On 17.04.2012 13:33, Dan Carpenter wrote:
Hi Antti,
Smatch complains about a potential information leak. I was hoping you
could take a look.
The patch de8e42035014: "[media] tda10071: NXP TDA10071 DVB-S/S2
driver" from Aug 1, 2011, leads to the following warning:
drivers/media/dvb/frontends/tda10071.c:322
tda10071_diseqc_send_master_cmd()
error: memcpy() 'diseqc_cmd->msg' too small (6 vs 16)
drivers/media/dvb/frontends/tda10071.c
290 if (diseqc_cmd->msg_len< 3 || diseqc_cmd->msg_len> 16) {
^^^^^^^^^^^^^^^^^^^^^^^^
We cap ->msg_len at 16 here. I wasn't able to figure out where the 16
came from. Or the 3 for that matter.
Those numbers are coming from include/linux/dvb/frontend.h struct
dvb_diseqc_master_cmd. And initially values are from the DiSEqC spec.
But you are correct, it is bug. Upper limit for message len should be 6
instead of 16 used currently. Likely just typo. Maybe I have done some
len testing during the development and changed it temporarily 6 => 16
and forgot switch back. Who knows...
291 ret = -EINVAL;
292 goto error;
293 }
294
295 /* wait LNB TX */
296 for (i = 500, tmp = 0; i&& !tmp; i--) {
297 ret = tda10071_rd_reg_mask(priv, 0x47,&tmp, 0x01);
298 if (ret)
299 goto error;
300
301 usleep_range(10000, 20000);
302 }
303
304 dbg("%s: loop=%d", __func__, i);
305
306 if (i == 0) {
307 ret = -ETIMEDOUT;
308 goto error;
309 }
310
311 ret = tda10071_wr_reg_mask(priv, 0x47, 0x00, 0x01);
312 if (ret)
313 goto error;
314
315 cmd.args[0x00] = CMD_LNB_SEND_DISEQC;
316 cmd.args[0x01] = 0;
317 cmd.args[0x02] = 0;
318 cmd.args[0x03] = 0;
319 cmd.args[0x04] = 2;
320 cmd.args[0x05] = 0;
321 cmd.args[0x06] = diseqc_cmd->msg_len;
322 memcpy(&cmd.args[0x07], diseqc_cmd->msg, diseqc_cmd->msg_len);
^^^^^^^^^^^^^^^
->msg is only 6 bytes long so we're copying past the end of the array.
Also cmd.arg is 0x1e (30) bytes long and we only copy 0x07 + 16 bytes
into it so it leaves the last 7 bytes of cmd.args unitialized. Btw,
why are the sizes specified in hex instead of decimal here?
323 cmd.len = 0x07 + diseqc_cmd->msg_len;
What it happens now is that garbage data will be send to DiSEqC switch -
in case of garbage data is sent from the user-space. Anyhow, I would
like to rather move these kind of common validly checking to the
DVB-core. Not only that case, but for the more commonly too. IMHO there
is currently too general checking left for the individual drivers...
And for the usage of hex numbering - I don't remember. Overall I prefer
hex numbering unless values are not clearly decimal ones, like
frequencies. But I agree indexing like that is seems more readable when
decimal numbering is used. I have generally used decimal numbering in
such cases.
Feel free to sent patch - or I will fix it someday later when suitable
time is found.
thanks,
Antti
-
http://palosaari.fi/
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