[PATCH 5.15 152/935] power: supply: cros_usbpd-charger: bound the EC-reported port count

5.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Bryam Vargas <redacted>

commit 48355ce49359740f52e94d3623f6fc557ce341f0 upstream.

cros_usbpd_charger_probe() reads two port counts from the EC and uses
one of them, num_charger_ports, as the loop bound when populating a
fixed-size array:

	struct port_data *ports[EC_USB_PD_MAX_PORTS];	/* 8 entries */
	...
	for (i = 0; i < charger->num_charger_ports; i++)
		charger->ports[charger->num_registered_psy++] = port;

Both num_usbpd_ports (from EC_CMD_USB_PD_PORTS) and num_charger_ports
(from EC_CMD_CHARGE_PORT_COUNT) are u8 values reported by the EC. The
only validation is a sanity check that compares the two EC-reported
values against each other:

	if (num_charger_ports < num_usbpd_ports ||
	    num_charger_ports > num_usbpd_ports + 1)
		return -EPROTO;

It never checks either count against EC_USB_PD_MAX_PORTS, the size of
the ports[] array. A malfunctioning, malicious or compromised EC that
reports num_usbpd_ports == num_charger_ports == N for any N > 8 (for
example both 255) passes this check, and the loop then writes N pointers
into the 8-entry ports[] array embedded in the devm_kzalloc()'d
charger_data, overflowing it by up to 255 - 8 = 247 entries (~1976
bytes): a slab out-of-bounds write.

Reject a port count larger than the ports[] array can hold.

Fixes: f68b883e8fad ("power: supply: add cros-ec USBPD charger driver.")
Cc: <redacted>
Signed-off-by: Bryam Vargas <redacted>
Reviewed-by: Tzung-Bi Shih <tzungbi@kernel.org>
Link: https://patch.msgid.link/20260616-b4-disp-5e197080-v2-1-8aa5bffce945@proton.me (local)
Signed-off-by: Sebastian Reichel <redacted>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/power/supply/cros_usbpd-charger.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/drivers/power/supply/cros_usbpd-charger.c
+++ b/drivers/power/supply/cros_usbpd-charger.c

@@ -600,10 +600,13 @@ static int cros_usbpd_charger_probe(stru
 
 	/*
 	 * Sanity checks on the number of ports:
-	 *  there should be at most 1 dedicated port
+	 *  there should be at most 1 dedicated port, and the count must
+	 *  not exceed the maximum number of supported ports
+	 *  (EC_USB_PD_MAX_PORTS).
 	 */
 	if (charger->num_charger_ports < charger->num_usbpd_ports ||
-	    charger->num_charger_ports > (charger->num_usbpd_ports + 1)) {
+	    charger->num_charger_ports > (charger->num_usbpd_ports + 1) ||
+	    charger->num_charger_ports > EC_USB_PD_MAX_PORTS) {
 		dev_err(dev, "Unexpected number of charge port count\n");
 		ret = -EPROTO;
 		goto fail_nowarn;