[PATCH v3] iio: proximity: hx9023s: validate firmware size

[Laxman Acharya Padhya]

hx9023s_send_cfg() copies the firmware into a counted flexible array and
then reads fixed offsets from the copied data before walking register/value
pairs starting at FW_DATA_OFFSET. A truncated firmware image can therefore
make the driver read past the copied buffer during probe-time configuration
loading.

Reject firmware images that cannot contain the fixed header, reject images
too large for the u16 fw_size field, and validate that the advertised
register count fits in the remaining payload.

Fixes: e9ed97be4fcc ("iio: proximity: hx9023s: Added firmware file
parsing functionality")
Cc: stable@xxxxxxxxxxxxxxx
Reviewed-by: Joshua Crofts <joshua.crofts1@xxxxxxxxx>
Signed-off-by: Laxman Acharya Padhya <acharyalaxman8848@xxxxxxxxx>
---
v3:
- Resend once in plain-text format after the duplicate v2 messages.
- Keep each commit trailer on one complete line.
---
 drivers/iio/proximity/hx9023s.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/proximity/hx9023s.c b/drivers/iio/proximity/hx9023s.c
index a6ff7cbe9e65..685053b84b34 100644
--- a/drivers/iio/proximity/hx9023s.c
+++ b/drivers/iio/proximity/hx9023s.c
@@ -18,6 +18,7 @@
 #include <linux/i2c.h>
 #include <linux/interrupt.h>
 #include <linux/irqreturn.h>
+#include <linux/limits.h>
 #include <linux/math64.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
@@ -1031,6 +1032,10 @@ static int hx9023s_bin_load(struct hx9023s_data
*data, struct hx9023s_bin *bin)

 static int hx9023s_send_cfg(const struct firmware *fw, struct
hx9023s_data *data)
 {
+ /* fw_size is u16 in struct hx9023s_bin, so reject truncation. */
+ if (fw->size < FW_DATA_OFFSET || fw->size > U16_MAX)
+ return -EINVAL;
+
  struct hx9023s_bin *bin __free(kfree) =
   kzalloc(fw->size + sizeof(*bin), GFP_KERNEL);
  if (!bin)
@@ -1041,7 +1046,8 @@ static int hx9023s_send_cfg(const struct
firmware *fw, struct hx9023s_data *data
  bin->fw_ver = bin->data[FW_VER_OFFSET];
  bin->reg_count = get_unaligned_le16(bin->data + FW_REG_CNT_OFFSET);

- release_firmware(fw);
+ if (bin->reg_count > (bin->fw_size - FW_DATA_OFFSET) / 2)
+ return -EINVAL;

  return hx9023s_bin_load(data, bin);
 }
@@ -1058,6 +1064,7 @@ static void hx9023s_cfg_update(const struct
firmware *fw, void *context)
  }

  ret = hx9023s_send_cfg(fw, data);
+ release_firmware(fw);
  if (ret) {
   dev_warn(dev, "Firmware update failed: %d\n", ret);
   goto no_fw;
-- 
2.51.2