ALSA: firewire-lib: Avoid division by zero in apply_constraint_to_size()

The step variable is initialized to zero. It is changed in the loop,
but if it's not changed it will remain zero. Add a variable check
before the division.

The observed behavior was introduced by commit 826b5de90c0b
("ALSA: firewire-lib: fix insufficient PCM rule for period/buffer size"),
and it is difficult to show that any of the interval parameters will
satisfy the snd_interval_test() condition with data from the
amdtp_rate_table[] table.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 826b5de90c0b ("ALSA: firewire-lib: fix insufficient PCM rule for period/buffer size")
Signed-off-by: Andrey Shumilin <shum.sdl@nppct.ru>
Reviewed-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://patch.msgid.link/20241018060018.1189537-1-shum.sdl@nppct.ru
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/firewire/amdtp-stream.c b/sound/firewire/amdtp-stream.c
index c72b2a75477598da7e08e1d4fead83a75d69de34..7fc51f829eccac2dde0a147a4c56d51943118c92 100644 (file)
--- a/sound/firewire/amdtp-stream.c
+++ b/sound/firewire/amdtp-stream.c
@@ -172,6 +172,9 @@ static int apply_constraint_to_size(struct snd_pcm_hw_params *params,
                        step = max(step, amdtp_syt_intervals[i]);
        }
 
+       if (step == 0)
+               return -EINVAL;
+
        t.min = roundup(s->min, step);
        t.max = rounddown(s->max, step);
        t.integer = 1;