2021-10-01 11:16:37

by Colin King

Subject: [PATCH][next] ALSA: usb-audio: Fix sum of uninitialized variable sample_accum

From: Colin Ian King <[email protected]>

Variable sample_accum is not being intialized and then has
ep->sample_rem added to it, leading to a bogus value. One solution
is to initialize it to zero at declaration time, but it is probably
best to just assign it to ep->sample_rem on first use.

Addresses-Coveriry: ("Uninitialized scalar variable")
Fixes: f0bd62b64016 ("ALSA: usb-audio: Improve frames size computation")
Signed-off-by: Colin Ian King <[email protected]>
---
sound/usb/endpoint.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index 42c0d2db8ba8..c6a33732db3f 100644
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -182,7 +182,7 @@ static int next_packet_size(struct snd_usb_endpoint *ep, unsigned int avail)
if (ep->fill_max)
return ep->maxframesize;

- sample_accum += ep->sample_rem;
+ sample_accum = ep->sample_rem;
if (sample_accum >= ep->pps) {
sample_accum -= ep->pps;
ret = ep->packsize[1];
--
2.32.0

2021-10-01 11:23:06

by Colin King

Subject: Re: [PATCH][next] ALSA: usb-audio: Fix sum of uninitialized variable sample_accum

On 01/10/2021 11:48, Takashi Iwai wrote:
> On Fri, 01 Oct 2021 12:44:17 +0200,
> Colin King wrote:
>>
>> From: Colin Ian King <[email protected]>
>>
>> Variable sample_accum is not being intialized and then has
>> ep->sample_rem added to it, leading to a bogus value. One solution
>> is to initialize it to zero at declaration time, but it is probably
>> best to just assign it to ep->sample_rem on first use.
>>
>> Addresses-Coveriry: ("Uninitialized scalar variable")
>> Fixes: f0bd62b64016 ("ALSA: usb-audio: Improve frames size computation")
>> Signed-off-by: Colin Ian King <[email protected]>
>
> Thanks for the patch, but it's no right fix. The Fixes tag points to
> a wrong commit, it was d215f63d49da9a8803af3e81acd6cad743686573
> ALSA: usb-audio: Check available frames for the next packet size
>
> And sample_accum has to be initialized from ep->sample_accum instead.
> I'll post the proper fix.

Thanks Takshi.

Colin

>
>
> Takashi
>
>
>> ---
>> sound/usb/endpoint.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
>> index 42c0d2db8ba8..c6a33732db3f 100644
>> --- a/sound/usb/endpoint.c
>> +++ b/sound/usb/endpoint.c
>> @@ -182,7 +182,7 @@ static int next_packet_size(struct snd_usb_endpoint *ep, unsigned int avail)
>> if (ep->fill_max)
>> return ep->maxframesize;
>>
>> - sample_accum += ep->sample_rem;
>> + sample_accum = ep->sample_rem;
>> if (sample_accum >= ep->pps) {
>> sample_accum -= ep->pps;
>> ret = ep->packsize[1];
>> --
>> 2.32.0
>>

2021-10-01 12:31:22

by Takashi Iwai

Subject: Re: [PATCH][next] ALSA: usb-audio: Fix sum of uninitialized variable sample_accum

On Fri, 01 Oct 2021 12:44:17 +0200,
Colin King wrote:
>
> From: Colin Ian King <[email protected]>
>
> Variable sample_accum is not being intialized and then has
> ep->sample_rem added to it, leading to a bogus value. One solution
> is to initialize it to zero at declaration time, but it is probably
> best to just assign it to ep->sample_rem on first use.
>
> Addresses-Coveriry: ("Uninitialized scalar variable")
> Fixes: f0bd62b64016 ("ALSA: usb-audio: Improve frames size computation")
> Signed-off-by: Colin Ian King <[email protected]>

Thanks for the patch, but it's no right fix. The Fixes tag points to
a wrong commit, it was d215f63d49da9a8803af3e81acd6cad743686573
ALSA: usb-audio: Check available frames for the next packet size

And sample_accum has to be initialized from ep->sample_accum instead.
I'll post the proper fix.


Takashi


> ---
> sound/usb/endpoint.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
> index 42c0d2db8ba8..c6a33732db3f 100644
> --- a/sound/usb/endpoint.c
> +++ b/sound/usb/endpoint.c
> @@ -182,7 +182,7 @@ static int next_packet_size(struct snd_usb_endpoint *ep, unsigned int avail)
> if (ep->fill_max)
> return ep->maxframesize;
>
> - sample_accum += ep->sample_rem;
> + sample_accum = ep->sample_rem;
> if (sample_accum >= ep->pps) {
> sample_accum -= ep->pps;
> ret = ep->packsize[1];
> --
> 2.32.0
>