Re: [PATCH] ALSA: firewire-lib: fix wrong value as length of header for CIP_NO_HEADER case

[Takashi Iwai <tiwai@suse.de>]

On Thu, 25 Jul 2024 18:08:21 +0200,
Gustavo A. R. Silva wrote:
> 
> 
> 
> On 25/07/24 09:56, Takashi Sakamoto wrote:
> > In a commit 1d717123bb1a ("ALSA: firewire-lib: Avoid
> > -Wflex-array-member-not-at-end warning"), DEFINE_FLEX() macro was used to
> > handle variable length of array for header field in struct fw_iso_packet
> > structure. The usage of macro has a side effect that the designated
> > initializer assigns the count of array to the given field. Therefore
> > CIP_HEADER_QUADLETS (=2) is assigned to struct fw_iso_packet.header,
> > while the original designated initializer assigns zero to all fields.
> > 
> > With CIP_NO_HEADER flag, the change causes invalid length of header in
> > isochronous packet for 1394 OHCI IT context. This bug affects all of
> > devices supported by ALSA fireface driver; RME Fireface 400, 800, UCX, UFX,
> > and 802.
> > 
> > This commit fixes the bug by replacing it with the alternative version of
> > macro which corresponds no initializer.
> 
> This change is incomplete. The patch I mention here[1] should also be applied.

Yes, but this can be fixed by another patch, right?
At least the regression introduced by the given commit can be fixed by
that.  The other fix can go through Sakamoto-san's firewire tree
individually.


thanks,

Takashi

> BTW, there is one more line that should probably be changed in `struct fw_iso_packet`
> to avoid further confusions:
> 
> -       u16 payload_length;     /* Length of indirect payload           */
> +       u16 payload_length;     /* Size of indirect payload             */
> 
> Thanks
> --
> Gustavo
> 
> [1] https://lore.kernel.org/linux-sound/dabb394e-6c85-45a0-bc06-7a45262a9a8c@embeddedor.com/T/#m0b9b0e7dd4561dc58422cf15df2dbd2ddb44b54b
> 
> > 
> > Cc: <stable@vger.kernel.org>
> > Fixes: 1d717123bb1a ("ALSA: firewire-lib: Avoid -Wflex-array-member-not-at-end warning")
> > Reported-by: Edmund Raile <edmund.raile@proton.me>
> > Closes: https://lore.kernel.org/r/rrufondjeynlkx2lniot26ablsltnynfaq2gnqvbiso7ds32il@qk4r6xps7jh2/
> > Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
> > ---
> >   sound/firewire/amdtp-stream.c | 3 +--
> >   1 file changed, 1 insertion(+), 2 deletions(-)
> > 
> > diff --git a/sound/firewire/amdtp-stream.c b/sound/firewire/amdtp-stream.c
> > index d35d0a420ee0..1a163bbcabd7 100644
> > --- a/sound/firewire/amdtp-stream.c
> > +++ b/sound/firewire/amdtp-stream.c
> > @@ -1180,8 +1180,7 @@ static void process_rx_packets(struct fw_iso_context *context, u32 tstamp, size_
> >   		(void)fw_card_read_cycle_time(fw_parent_device(s->unit)->card, &curr_cycle_time);
> >     	for (i = 0; i < packets; ++i) {
> > -		DEFINE_FLEX(struct fw_iso_packet, template, header,
> > -			    header_length, CIP_HEADER_QUADLETS);
> > +		DEFINE_RAW_FLEX(struct fw_iso_packet, template, header, CIP_HEADER_QUADLETS);
> >   		bool sched_irq = false;
> >     		build_it_pkt_header(s, desc->cycle, template,
> > pkt_header_length,