2018-05-07 23:09:25

by Colin King

Subject: [PATCH][media-next] media: ddbridge: avoid out-of-bounds write on array demod_in_use

From: Colin Ian King <[email protected]>

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 <[email protected]>
---
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;
--
2.17.0

2018-05-08 10:39:15

by Daniel Scheller

Subject: Re: [PATCH][media-next] media: ddbridge: avoid out-of-bounds write on array demod_in_use

Hi Colin,

Am Tue, 8 May 2018 00:08:42 +0100
schrieb Colin King <[email protected]>:

> From: Colin Ian King <[email protected]>
>
> 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 <[email protected]>
> ---
> 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).

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

Best regards,
Daniel Scheller
--
https://github.com/herrnst

2018-05-08 10:40:31

by Colin King

Subject: Re: [PATCH][media-next] media: ddbridge: avoid out-of-bounds write on array demod_in_use

On 08/05/18 11:38, Daniel Scheller wrote:
> Hi Colin,
>
> Am Tue, 8 May 2018 00:08:42 +0100
> schrieb Colin King <[email protected]>:
>
>> From: Colin Ian King <[email protected]>
>>
>> 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 <[email protected]>
>> ---
>> 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
>

2018-05-09 20:15:23

by Daniel Scheller

Subject: Re: [PATCH][media-next] media: ddbridge: avoid out-of-bounds write on array demod_in_use

Hi Colin,

Am Tue, 8 May 2018 11:39:56 +0100
schrieb Colin Ian King <[email protected]>:

> On 08/05/18 11:38, Daniel Scheller wrote:
> > Hi Colin,
> >
> > Am Tue, 8 May 2018 00:08:42 +0100
> > schrieb Colin King <[email protected]>:
> >
> >> From: Colin Ian King <[email protected]>
> >>
> >> 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 <[email protected]>
> >> ---
> >> 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!

JFYI, patch sent as part of a few other fixes and up at linux-media
patchwork:

https://patchwork.linuxtv.org/patch/49403/

Best regards,
Daniel Scheller
--
https://github.com/herrnst