[PATCH v2 4/4] soc: qcom: geni-se: Fix write to read-only firmware buffer

[Viken Dadhaniya <viken.dadhaniya@oss.qualcomm.com>]

geni_find_protocol_fw() casts fw->data to a non-const struct se_fw_hdr
pointer and writes back the rounded-up fw_size value:

        sefw->fw_size_in_items = cpu_to_le16(fw_size);

The firmware subsystem maps the firmware blob read-only. Writing through
the cast pointer causes a level-3 permission fault on AArch64 and
crashes the kernel during driver probe.

The write-back is no longer necessary: the previous commit propagates
the rounded size to the caller via fw_size_out. Remove the write-back
and make sefw (and the hdr pointer in the caller) const-correct.

Fixes: d4bf06592ad6 ("soc: qcom: geni-se: Add support to load QUP SE Firmware via Linux subsystem")
Cc: stable@vger.kernel.org
Signed-off-by: Viken Dadhaniya <viken.dadhaniya@oss.qualcomm.com>
---
 drivers/soc/qcom/qcom-geni-se.c | 22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/drivers/soc/qcom/qcom-geni-se.c b/drivers/soc/qcom/qcom-geni-se.c
index 11ca8223fbcd..6ac2bdc16984 100644
--- a/drivers/soc/qcom/qcom-geni-se.c
+++ b/drivers/soc/qcom/qcom-geni-se.c
@@ -1238,17 +1238,17 @@ EXPORT_SYMBOL_GPL(geni_se_resources_init);
  * controller. Validates the firmware size against the hardware PROG_RAM_DEPTH
  * read from SE_HW_PARAM_2.
  *
- * Return: pointer to a valid 'struct se_fw_hdr' if found, or NULL otherwise.
+ * Return: pointer to a valid 'const struct se_fw_hdr' if found, or NULL otherwise.
  */
-static struct se_fw_hdr *geni_find_protocol_fw(struct geni_se *se, const struct firmware *fw,
-					       enum geni_se_protocol_type protocol,
-					       u32 *fw_size_out)
+static const struct se_fw_hdr *geni_find_protocol_fw(struct geni_se *se, const struct firmware *fw,
+						     enum geni_se_protocol_type protocol,
+						     u32 *fw_size_out)
 {
 	struct device *dev = se->dev;
 	const struct elf32_hdr *ehdr;
 	const struct elf32_phdr *phdrs;
 	const struct elf32_phdr	*phdr;
-	struct se_fw_hdr *sefw;
+	const struct se_fw_hdr *sefw;
 	u32 fw_end, cfg_idx_end, cfg_val_end;
 	u32 prog_ram_depth;
 	u32 fw_size;
@@ -1290,7 +1290,7 @@ static struct se_fw_hdr *geni_find_protocol_fw(struct geni_se *se, const struct
 		if (phdr->p_filesz < sizeof(struct se_fw_hdr))
 			continue;
 
-		sefw = (struct se_fw_hdr *)(fw->data + phdr->p_offset);
+		sefw = (const struct se_fw_hdr *)(fw->data + phdr->p_offset);
 		fw_size = le16_to_cpu(sefw->fw_size_in_items);
 
 		if (le32_to_cpu(sefw->magic) != SE_MAGIC_NUM || le32_to_cpu(sefw->version) != 1)
@@ -1299,10 +1299,8 @@ static struct se_fw_hdr *geni_find_protocol_fw(struct geni_se *se, const struct
 		if (le16_to_cpu(sefw->serial_protocol) != protocol)
 			continue;
 
-		if (fw_size % 2 != 0) {
+		if (fw_size % 2 != 0)
 			fw_size++;
-			sefw->fw_size_in_items = cpu_to_le16(fw_size);
-		}
 
 		fw_end = le16_to_cpu(sefw->fw_offset) + fw_size * sizeof(u32);
 		cfg_idx_end = le16_to_cpu(sefw->cfg_idx_offset) +
@@ -1437,15 +1435,15 @@ static int geni_load_se_fw(struct geni_se *se, const struct firmware *fw,
 	const u8 *cfg_idx_arr;
 	u32 i, reg_value, fw_size_in_items;
 	int ret;
-	struct se_fw_hdr *hdr;
+	const struct se_fw_hdr *hdr;
 
 	hdr = geni_find_protocol_fw(se, fw, protocol, &fw_size_in_items);
 	if (!hdr)
 		return -EINVAL;
 
-	fw_data = (const u32 *)((u8 *)hdr + le16_to_cpu(hdr->fw_offset));
+	fw_data = (const u32 *)((const u8 *)hdr + le16_to_cpu(hdr->fw_offset));
 	cfg_idx_arr = (const u8 *)hdr + le16_to_cpu(hdr->cfg_idx_offset);
-	cfg_val_arr = (const u32 *)((u8 *)hdr + le16_to_cpu(hdr->cfg_val_offset));
+	cfg_val_arr = (const u32 *)((const u8 *)hdr + le16_to_cpu(hdr->cfg_val_offset));
 
 	ret = geni_icc_set_bw(se);
 	if (ret)

-- 
2.34.1