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

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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 <colin.king@xxxxxxxxxxxxx>

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 <colin.king@xxxxxxxxxxxxx>

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





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