[PATCH 4/4] ALSA: compress: prevent potential divide by zero bugs

Dan Carpenter
2018-12-21T09:06:58Z

The problem is seen in the q6asm_dai_compr_set_params() function:

ret = q6asm_map_memory_regions(dir, prtd->audio_client, prtd->phys,
(prtd->pcm_size / prtd->periods),
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
prtd->periods);

In this code prtd->pcm_size is the buffer_size and prtd->periods comes
from params->buffer.fragments. If we allow the number of fragments to
be zero then it results in a divide by zero bug. One possible fix would
be to use prtd->pcm_count directly instead of using the division to
re-calculate it. But I decided that it doesn't really make sense to
allow zero fragments.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
I am not very sure of this patch. Please review it extra carefully
because it is an API change.

sound/core/compress_offload.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/sound/core/compress_offload.c b/sound/core/compress_offload.c
index a5b09e75e787..f7d2b373da0a 100644
--- a/sound/core/compress_offload.c
+++ b/sound/core/compress_offload.c
@@ -541,7 +541,8 @@ static int snd_compress_check_input(struct snd_compr_params *params)
{
/* first let's check the buffer parameter's */
if (params->buffer.fragment_size = 0 ||
- params->buffer.fragments > INT_MAX / params->buffer.fragment_size)
+ params->buffer.fragments > INT_MAX / params->buffer.fragment_size ||
+ params->buffer.fragments = 0)
return -EINVAL;

/* now codec parameters */
--
2.17.1