From: Takashi Iwai <ti...@suse.de>

commit 11cb881bf075cea41092a20236ba708b18e1dbb2 upstream.

There are a few places that call round{up|down}_pow_of_two() with the
value zero, and this causes undefined behavior warnings.  Avoid
calling those macros if such a nonsense value is passed; it's a minor
optimization as well, as we handle it as either an error or a value to
be skipped, instead.

Reported-by: syzbot+33ef0b6639a8d2d42...@syzkaller.appspotmail.com
Cc: <sta...@vger.kernel.org>
Link: https://lore.kernel.org/r/20201218161730.26596-1-ti...@suse.de
Signed-off-by: Takashi Iwai <ti...@suse.de>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 sound/core/oss/pcm_oss.c |   22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

--- a/sound/core/oss/pcm_oss.c
+++ b/sound/core/oss/pcm_oss.c
@@ -708,6 +708,8 @@ static int snd_pcm_oss_period_size(struc
 
        oss_buffer_size = snd_pcm_plug_client_size(substream,
                                                   
snd_pcm_hw_param_value_max(slave_params, SNDRV_PCM_HW_PARAM_BUFFER_SIZE, NULL)) 
* oss_frame_size;
+       if (!oss_buffer_size)
+               return -EINVAL;
        oss_buffer_size = rounddown_pow_of_two(oss_buffer_size);
        if (atomic_read(&substream->mmap_count)) {
                if (oss_buffer_size > runtime->oss.mmap_bytes)
@@ -743,17 +745,21 @@ static int snd_pcm_oss_period_size(struc
 
        min_period_size = snd_pcm_plug_client_size(substream,
                                                   
snd_pcm_hw_param_value_min(slave_params, SNDRV_PCM_HW_PARAM_PERIOD_SIZE, NULL));
-       min_period_size *= oss_frame_size;
-       min_period_size = roundup_pow_of_two(min_period_size);
-       if (oss_period_size < min_period_size)
-               oss_period_size = min_period_size;
+       if (min_period_size) {
+               min_period_size *= oss_frame_size;
+               min_period_size = roundup_pow_of_two(min_period_size);
+               if (oss_period_size < min_period_size)
+                       oss_period_size = min_period_size;
+       }
 
        max_period_size = snd_pcm_plug_client_size(substream,
                                                   
snd_pcm_hw_param_value_max(slave_params, SNDRV_PCM_HW_PARAM_PERIOD_SIZE, NULL));
-       max_period_size *= oss_frame_size;
-       max_period_size = rounddown_pow_of_two(max_period_size);
-       if (oss_period_size > max_period_size)
-               oss_period_size = max_period_size;
+       if (max_period_size) {
+               max_period_size *= oss_frame_size;
+               max_period_size = rounddown_pow_of_two(max_period_size);
+               if (oss_period_size > max_period_size)
+                       oss_period_size = max_period_size;
+       }
 
        oss_periods = oss_buffer_size / oss_period_size;
 


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