[PATCH] ALSA: hdsp: Fix divide-by-zero in DDS offset control

[songxiebing]

From: Bob Song <songxiebing@xxxxxxxxxx>

hdsp_set_dds_offset() computes the target rate as
system_sample_rate + offset_hz without validating the result.  A user
can set the DDS offset to -system_sample_rate through the control API,
making rate zero and causing div_u64() in hdsp_set_dds_value() to
divide by zero.

Reject non-positive rates before programming the DDS value.

Fixes: e4b6088c8cf1 ("[ALSA] hdsp - Add support for fine tuning of sample rate support to HDSP 9632")
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Bob Song <songxiebing@xxxxxxxxxx>
---
 sound/pci/rme9652/hdsp.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/sound/pci/rme9652/hdsp.c b/sound/pci/rme9652/hdsp.c
index 7dce548b9f36..694816f966d2 100644
--- a/sound/pci/rme9652/hdsp.c
+++ b/sound/pci/rme9652/hdsp.c
@@ -2802,6 +2802,9 @@ static int hdsp_dds_offset(struct hdsp *hdsp)
 static int hdsp_set_dds_offset(struct hdsp *hdsp, int offset_hz)
 {
 	int rate = hdsp->system_sample_rate + offset_hz;
+
+	if (rate <= 0)
+		return -EINVAL;
 	hdsp_set_dds_value(hdsp, rate);
 	return 0;
 }
-- 
2.25.1