usb: typec: ucsi: ccg: reject firmware images without a ':' record header

do_flash() locates the first .cyacd record with

	p = strnchr(fw->data, fw->size, ':');
	while (p < eof) {
		s = strnchr(p + 1, eof - p - 1, ':');
		...
	}

If the firmware image contains no ':' byte, strnchr() returns NULL. NULL compares less than the valid kernel pointer eof, so the loop body runs and strnchr() is called with p + 1 == (void *)1 and a length of roughly (unsigned long)eof, causing a wonderful crash.

The not_signed_fw fallthrough earlier in do_flash() and the chip-state branches in ccg_fw_update_needed() allow an unsigned blob to reach this loop, so a root user who can place a crafted file under /lib/firmware and write the do_flash sysfs attribute can trigger the oops.

Bail out with -EINVAL when the initial strnchr() returns NULL.

Assisted-by gkh_clanker_t1000

Cc stable <[email protected]>

Cc Heikki Krogerus <[email protected]>

Signed-off-by Greg Kroah-Hartman <[email protected]>

---
 drivers/usb/typec/ucsi/ucsi_ccg.c | 5 +++++
 1 file changed, 5 insertions(+)

drivers/usb/typec/ucsi/ucsi_ccg.c +5 -0

index 199799b319c2..4463c1ae96bd 100644
@@ -1243,6 +1243,11 @@ static int do_flash(struct ucsi_ccg *uc, enum enum_flash_mode mode)
 	 *****************************************************************/
 
 	p = strnchr(fw->data, fw->size, ':');
+	if (!p) {
+		dev_err(dev, "Bad FW format: no ':' record header found\n");
+		err = -EINVAL;
+		goto release_mem;
+	}
 	while (p < eof) {
 		s = strnchr(p + 1, eof - p - 1, ':');
 

Signature · 1 line

2.54.0