Linux vulnerability

What happened

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.

Affected versions

Linux: f68b883e8fad23ed0ac4756d91594809d78678ed through before fd29d08ee487f3bf50f2575aaa74f78a74b09b21 (git); f68b883e8fad23ed0ac4756d91594809d78678ed through before 78be8b7403ff7638162438b664a07d19da76059e (git); f68b883e8fad23ed0ac4756d91594809d78678ed through before 3d1e01443b221081258ff34ea0cdd0431e4ff62e (git); f68b883e8fad23ed0ac4756d91594809d78678ed through before 48355ce49359740f52e94d3623f6fc557ce341f0 (git); 4.19 Fixed: See vendor advisory.

Why it matters

Review the vendor advisory and exposure of the affected product to determine operational impact.

Detection & mitigation

• Apply vendor-provided updates or mitigations.
• Review affected product exposure and access logs.