linux-kernel - [PATCH] firmware: cs_dsp: Fix overrun of unterminated control name string

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Date:   Tue, 12 Apr 2022 17:39:27 +0100
From:   Richard Fitzgerald <rf@...nsource.cirrus.com>
To:     <broonie@...nel.org>
CC:     <patches@...nsource.cirrus.com>, <linux-kernel@...r.kernel.org>,
        <alsa-devel@...a-project.org>,
        Richard Fitzgerald <rf@...nsource.cirrus.com>
Subject: [PATCH] firmware: cs_dsp: Fix overrun of unterminated control name string

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@...nsource.cirrus.com>
Fixes: f6bc909e7673 ("firmware: cs_dsp: add driver to support firmware loading on Cirrus Logic DSPs")
---
 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;
-- 
2.30.2