[PATCH v2] usb: typec: ucsi: displayport: Fix OOB altmode array index
From: Jameson Thies
Date: Fri Sep 04 2026 - 19:44:16 EST
The UCSI displayport driver indexes the connector's port altmode array
with the GET_CURRENT_CAM response after checking it is not 0xff. The
port altmode array is UCSI_MAX_ALTMODES elements long. If the PPM
returns an invalid GET_CURRENT_CAM response above UCSI_MAX_ALTMODES and
not equal to 0xff, the kernel may crash with an array index OOB error.
Update the UCSI displayport driver to verify the current cam is less
than UCSI_MAX_ALTMODES before accessing the port altmode array.
Fixes: af8622f6a585 ("usb: typec: ucsi: Support for DisplayPort alt mode")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Jameson Thies <jthies@xxxxxxxxxx>
---
Changes in v2:
- removed 0xff alt mode assignement when GET_CURRENT_CAM returns an error.
- return -EINVAL when alt mode index above UCSI_MAX_ALTMODES is returned.
drivers/usb/typec/ucsi/displayport.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/drivers/usb/typec/ucsi/displayport.c b/drivers/usb/typec/ucsi/displayport.c
index 7067f2561b84..572da7bbd29c 100644
--- a/drivers/usb/typec/ucsi/displayport.c
+++ b/drivers/usb/typec/ucsi/displayport.c
@@ -71,11 +71,14 @@ static int ucsi_displayport_enter(struct typec_altmode *alt, u32 *vdo)
if (ret < 0) {
if (ucsi->version > 0x0100)
goto err_unlock;
- cur = 0xff;
}
if (cur != 0xff) {
- ret = dp->con->port_altmode[cur] == alt ? 0 : -EBUSY;
+ if (cur < UCSI_MAX_ALTMODES)
+ ret = dp->con->port_altmode[cur] == alt ? 0 : -EBUSY;
+ else
+ ret = -EINVAL;
+
goto err_unlock;
}
base-commit: cee9395acd8043be0644b25c34bfa86623f2b935
--
2.55.0.979.g7e5102b832-goog