linux-kernel - [PATCH 1/4] firmware: cs_dsp: Fix overflow checking of wmfw header

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Date: Thu, 27 Jun 2024 15:14:29 +0100
From: Richard Fitzgerald <rf@...nsource.cirrus.com>
To: <broonie@...nel.org>
CC: <linux-kernel@...r.kernel.org>, <patches@...nsource.cirrus.com>,
        <alsa-devel@...a-project.org>, <linux-sound@...r.kernel.org>
Subject: [PATCH 1/4] firmware: cs_dsp: Fix overflow checking of wmfw header

Fix the checking that firmware file buffer is large enough for the
wmfw header, to prevent overrunning the buffer.

The original code tested that the firmware data buffer contained
enough bytes for the sums of the size of the structs

	wmfw_header + wmfw_adsp1_sizes + wmfw_footer

But wmfw_adsp1_sizes is only used on ADSP1 firmware. For ADSP2 and
Halo Core the equivalent struct is wmfw_adsp2_sizes, which is
4 bytes longer. So the length check didn't guarantee that there
are enough bytes in the firmware buffer for a header with
wmfw_adsp2_sizes.

This patch splits the length check into three separate parts. Each
of the wmfw_header, wmfw_adsp?_sizes and wmfw_footer are checked
separately before they are used.

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 | 25 ++++++++++++++++++-------
 1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/drivers/firmware/cirrus/cs_dsp.c b/drivers/firmware/cirrus/cs_dsp.c
index 0d139e4de37c..6eca62d31e20 100644
--- a/drivers/firmware/cirrus/cs_dsp.c
+++ b/drivers/firmware/cirrus/cs_dsp.c
@@ -1321,6 +1321,10 @@ static unsigned int cs_dsp_adsp1_parse_sizes(struct cs_dsp *dsp,
 	const struct wmfw_adsp1_sizes *adsp1_sizes;
 
 	adsp1_sizes = (void *)&firmware->data[pos];
+	if (sizeof(*adsp1_sizes) > firmware->size - pos) {
+		cs_dsp_err(dsp, "%s: file truncated\n", file);
+		return 0;
+	}
 
 	cs_dsp_dbg(dsp, "%s: %d DM, %d PM, %d ZM\n", file,
 		   le32_to_cpu(adsp1_sizes->dm), le32_to_cpu(adsp1_sizes->pm),
@@ -1337,6 +1341,10 @@ static unsigned int cs_dsp_adsp2_parse_sizes(struct cs_dsp *dsp,
 	const struct wmfw_adsp2_sizes *adsp2_sizes;
 
 	adsp2_sizes = (void *)&firmware->data[pos];
+	if (sizeof(*adsp2_sizes) > firmware->size - pos) {
+		cs_dsp_err(dsp, "%s: file truncated\n", file);
+		return 0;
+	}
 
 	cs_dsp_dbg(dsp, "%s: %d XM, %d YM %d PM, %d ZM\n", file,
 		   le32_to_cpu(adsp2_sizes->xm), le32_to_cpu(adsp2_sizes->ym),
@@ -1376,7 +1384,6 @@ static int cs_dsp_load(struct cs_dsp *dsp, const struct firmware *firmware,
 	struct regmap *regmap = dsp->regmap;
 	unsigned int pos = 0;
 	const struct wmfw_header *header;
-	const struct wmfw_adsp1_sizes *adsp1_sizes;
 	const struct wmfw_footer *footer;
 	const struct wmfw_region *region;
 	const struct cs_dsp_region *mem;
@@ -1392,10 +1399,8 @@ static int cs_dsp_load(struct cs_dsp *dsp, const struct firmware *firmware,
 
 	ret = -EINVAL;
 
-	pos = sizeof(*header) + sizeof(*adsp1_sizes) + sizeof(*footer);
-	if (pos >= firmware->size) {
-		cs_dsp_err(dsp, "%s: file too short, %zu bytes\n",
-			   file, firmware->size);
+	if (sizeof(*header) >= firmware->size) {
+		ret = -EOVERFLOW;
 		goto out_fw;
 	}
 
@@ -1423,13 +1428,16 @@ static int cs_dsp_load(struct cs_dsp *dsp, const struct firmware *firmware,
 
 	pos = sizeof(*header);
 	pos = dsp->ops->parse_sizes(dsp, file, pos, firmware);
+	if ((pos == 0) || (sizeof(*footer) > firmware->size - pos)) {
+		ret = -EOVERFLOW;
+		goto out_fw;
+	}
 
 	footer = (void *)&firmware->data[pos];
 	pos += sizeof(*footer);
 
 	if (le32_to_cpu(header->len) != pos) {
-		cs_dsp_err(dsp, "%s: unexpected header length %d\n",
-			   file, le32_to_cpu(header->len));
+		ret = -EOVERFLOW;
 		goto out_fw;
 	}
 
@@ -1555,6 +1563,9 @@ static int cs_dsp_load(struct cs_dsp *dsp, const struct firmware *firmware,
 	cs_dsp_buf_free(&buf_list);
 	kfree(text);
 
+	if (ret == -EOVERFLOW)
+		cs_dsp_err(dsp, "%s: file content overflows file data\n", file);
+
 	return ret;
 }
 
-- 
2.39.2