Hi,
On Thu, Apr 06, 2023 at 06:28:01AM -0700, Xu Biang wrote:
> Smatch Warns:
> sound/firewire/tascam/tascam-stream.c:493 snd_tscm_stream_start_duplex()
> warn: missing unwind goto?
>
> The direct return will cause the stream list of "&tscm->domain" unemptied
> and the session in "tscm" unfinished if amdtp_domain_start() returns with
> an error.
>
> Fix this by changing the direct return to a goto which will empty the
> stream list of "&tscm->domain" and finish the session in "tscm".
>
> The snd_tscm_stream_start_duplex() function is called in the prepare
> callback of PCM. According to "ALSA Kernel API Documentation", the prepare
> callback of PCM will be called many times at each setup. So, if the
> "&d->streams" list is not emptied, when the prepare callback is called
> next time, snd_tscm_stream_start_duplex() will receive -EBUSY from
> amdtp_domain_add_stream() that tries to add an existing stream to the
> domain. The error handling code after the "error" label will be executed
> in this case, and the "&d->streams" list will be emptied. So not emptying
> the "&d->streams" list will not cause an issue. But it is more efficient
> and readable to empty it on the first error by changing the direct return
> to a goto statement.
>
> The session in "tscm" has been begun before amdtp_domain_start(), so it
> needs to be finished when amdtp_domain_start() fails.
>
> Fixes: c281d46a51e3 ("ALSA: firewire-tascam: support AMDTP domain")
> Signed-off-by: Xu Biang <xubiang@xxxxxxxxxxx>
> Reviewed-by: Dan Carpenter <error27@xxxxxxxxx>
> ---
> Note that this finding is from static analysis and not tested.
>
> sound/firewire/tascam/tascam-stream.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
Indeed. I overlooked it when posting the patch. The bug exists Linux
kernel v5.4 or later and the fix should be forward to stable kernels.
Acked-by: Takashi Sakamoto <o-takashi@xxxxxxxxxxxxx>
> diff --git a/sound/firewire/tascam/tascam-stream.c b/sound/firewire/tascam/tascam-stream.c
> index 53e094cc411f..dfe783d01d7d 100644
> --- a/sound/firewire/tascam/tascam-stream.c
> +++ b/sound/firewire/tascam/tascam-stream.c
> @@ -490,7 +490,7 @@ int snd_tscm_stream_start_duplex(struct snd_tscm *tscm, unsigned int rate)
> // packet is important for media clock recovery.
> err = amdtp_domain_start(&tscm->domain, tx_init_skip_cycles, true, true);
> if (err < 0)
> - return err;
> + goto error;
>
> if (!amdtp_domain_wait_ready(&tscm->domain, READY_TIMEOUT_MS)) {
> err = -ETIMEDOUT;
> --
> 2.17.1
Thanks
Takashi Sakamoto
