LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Colin Ian King <colin.king@canonical.com>
To: Daniel Scheller <d.scheller.oss@gmail.com>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>,
	linux-media@vger.kernel.org, kernel-janitors@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH][media-next] media: ddbridge: avoid out-of-bounds write on array demod_in_use
Date: Tue, 8 May 2018 11:39:56 +0100	[thread overview]
Message-ID: <c7ea26b7-d743-f2bd-fd0d-41421ae2778d@canonical.com> (raw)
In-Reply-To: <20180508123836.0b5c2f7f@lt530>

On 08/05/18 11:38, Daniel Scheller wrote:
> Hi Colin,
> 
> Am Tue,  8 May 2018 00:08:42 +0100
> schrieb Colin King <colin.king@canonical.com>:
> 
>> From: Colin Ian King <colin.king@canonical.com>
>>
>> In function stop there is a check to see if state->demod is a stopped
>> value of 0xff, however, later on, array demod_in_use is indexed with
>> this value causing an out-of-bounds write error.  Avoid this by only
>> writing to array demod_in_use if state->demod is not set to the stopped
>> sentinal value for this specific corner case.  Also, replace the magic
>> value 0xff with DEMOD_STOPPED to make code more readable.
>>
>> Detected by CoverityScan, CID#1468550 ("Out-of-bounds write")
>>
>> Fixes: daeeb1319e6f ("media: ddbridge: initial support for MCI-based MaxSX8 cards")
>> Signed-off-by: Colin Ian King <colin.king@canonical.com>
>> ---
>>  drivers/media/pci/ddbridge/ddbridge-mci.c | 11 +++++++----
>>  1 file changed, 7 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/media/pci/ddbridge/ddbridge-mci.c b/drivers/media/pci/ddbridge/ddbridge-mci.c
>> index a85ff3e6b919..1f5ed53c8d35 100644
>> --- a/drivers/media/pci/ddbridge/ddbridge-mci.c
>> +++ b/drivers/media/pci/ddbridge/ddbridge-mci.c
>> @@ -20,6 +20,8 @@
>>  #include "ddbridge-io.h"
>>  #include "ddbridge-mci.h"
>>  
>> +#define DEMOD_STOPPED	(0xff)
>> +
>>  static LIST_HEAD(mci_list);
>>  
>>  static const u32 MCLK = (1550000000 / 12);
>> @@ -193,7 +195,7 @@ static int stop(struct dvb_frontend *fe)
>>  	u32 input = state->tuner;
>>  
>>  	memset(&cmd, 0, sizeof(cmd));
>> -	if (state->demod != 0xff) {
>> +	if (state->demod != DEMOD_STOPPED) {
>>  		cmd.command = MCI_CMD_STOP;
>>  		cmd.demod = state->demod;
>>  		mci_cmd(state, &cmd, NULL);
>> @@ -209,10 +211,11 @@ static int stop(struct dvb_frontend *fe)
>>  	state->base->tuner_use_count[input]--;
>>  	if (!state->base->tuner_use_count[input])
>>  		mci_set_tuner(fe, input, 0);
>> -	state->base->demod_in_use[state->demod] = 0;
>> +	if (state->demod != DEMOD_STOPPED)
>> +		state->base->demod_in_use[state->demod] = 0;
>>  	state->base->used_ldpc_bitrate[state->nr] = 0;
>> -	state->demod = 0xff;
>> -	state->base->assigned_demod[state->nr] = 0xff;
>> +	state->demod = DEMOD_STOPPED;
>> +	state->base->assigned_demod[state->nr] = DEMOD_STOPPED;
>>  	state->base->iq_mode = 0;
>>  	mutex_unlock(&state->base->tuner_lock);
>>  	state->started = 0;
> 
> Thanks for the patch, or - better - pointing this out. While it's
> unlikely this will ever be an issue, I'm fine with changing the code
> like that, but I'd prefer to change it a bit differently (ie.
> DEMOD_STOPPED should be DEMOD_UNUSED, and I'd add defines for max.
> tuners and use/compare against them).

Sounds like a good idea.

> 
> I'll send out a different patch that will cover the potential
> coverityscan problem throughout the end of the week.

Great. Thanks!

> 
> Best regards,
> Daniel Scheller
> 

  reply	other threads:[~2018-05-08 10:40 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-07 23:08 Colin King
2018-05-08 10:38 ` Daniel Scheller
2018-05-08 10:39   ` Colin Ian King [this message]
2018-05-09 20:13     ` Daniel Scheller

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=c7ea26b7-d743-f2bd-fd0d-41421ae2778d@canonical.com \
    --to=colin.king@canonical.com \
    --cc=d.scheller.oss@gmail.com \
    --cc=kernel-janitors@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-media@vger.kernel.org \
    --cc=mchehab@kernel.org \
    --subject='Re: [PATCH][media-next] media: ddbridge: avoid out-of-bounds write on array demod_in_use' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).