[PATCH v1] usb: typec: ucsi: displayport: Fix OOB altmode array index

[Jameson Thies <jthies@google.com>]

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@vger.kernel.org
Signed-off-by: Jameson Thies <jthies@google.com>
---
 drivers/usb/typec/ucsi/displayport.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/typec/ucsi/displayport.c b/drivers/usb/typec/ucsi/displayport.c
index 7067f2561b84..8d2032d0762c 100644
--- a/drivers/usb/typec/ucsi/displayport.c
+++ b/drivers/usb/typec/ucsi/displayport.c
@@ -74,7 +74,7 @@ static int ucsi_displayport_enter(struct typec_altmode *alt, u32 *vdo)
 		cur = 0xff;
 	}
 
-	if (cur != 0xff) {
+	if (cur < UCSI_MAX_ALTMODES) {
 		ret = dp->con->port_altmode[cur] == alt ? 0 : -EBUSY;
 		goto err_unlock;
 	}

base-commit: e1e6e541c5c9cf548e9fdc35fc26808c82074440
-- 
2.55.0.860.g4b6b3295ed-goog