[PATCH 5.17 021/146] firmware: cs_dsp: Fix overrun of unterminated control name string

[Greg Kroah-Hartman]

From: Richard Fitzgerald <rf@xxxxxxxxxxxxxxxxxxxxx>

[ Upstream commit 5b933c7262c5b0ea11ea3c3b3ea81add04895954 ]

For wmfw format v2 and later the coefficient name strings have a length
field and are NOT null-terminated. Use kasprintf() to convert the
unterminated string into a null-terminated string in an allocated buffer.

The previous code handled this duplication incorrectly using kmemdup()
and getting the length from a strlen() of the (unterminated) source string.
This resulted in creating a string that continued up to the next byte in
the firmware file that just happened to be 0x00.

Signed-off-by: Richard Fitzgerald <rf@xxxxxxxxxxxxxxxxxxxxx>
Fixes: f6bc909e7673 ("firmware: cs_dsp: add driver to support firmware loading on Cirrus Logic DSPs")
Link: https://lore.kernel.org/r/20220412163927.1303470-1-rf@xxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/firmware/cirrus/cs_dsp.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/firmware/cirrus/cs_dsp.c b/drivers/firmware/cirrus/cs_dsp.c
index e48108e694f8..7dad6f57d970 100644
--- a/drivers/firmware/cirrus/cs_dsp.c
+++ b/drivers/firmware/cirrus/cs_dsp.c
@@ -955,8 +955,7 @@ static int cs_dsp_create_control(struct cs_dsp *dsp,
 	ctl->alg_region = *alg_region;
 	if (subname && dsp->fw_ver >= 2) {
 		ctl->subname_len = subname_len;
-		ctl->subname = kmemdup(subname,
-				       strlen(subname) + 1, GFP_KERNEL);
+		ctl->subname = kasprintf(GFP_KERNEL, "%.*s", subname_len, subname);
 		if (!ctl->subname) {
 			ret = -ENOMEM;
 			goto err_ctl;
-- 
2.35.1