Overview
About vulnerability
In the Linux kernel, the following vulnerability has been resolved:
power: supply: cros_usbpd-charger: bound the EC-reported port count
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.
Details
- Affected product:
- Debian 10 ELS , Debian 11 ELS , Ubuntu 20.04 ELS
- Affected packages:
- linux @ 5.10.259 (+3 more)