CVE-2026-63960

In the Linux kernel, the following vulnerability has been resolved:

usb: typec: wcove: don't write past struct pdmessage in wcovereadrxbuffer()

wcovereadrxbuffer() copies the PD RX FIFO into the caller's struct pdmessage with

for (i = 0; i < USBC_RXINFO_RXBYTES(info); i++)
    regmap_read(wcove->regmap, USBC_RX_DATA + i, msg + i);

which has two problems:

USBCRXINFORXBYTES() is a 5-bit field (max 31) while struct pd_message is 30 bytes (__le16 header + __le32 payload[PDMAXPAYLOAD], packed). The byte count latched in RXINFO is the number of bytes the port partner put on the wire, so a malicious partner that transmits a 31-byte frame can drive the loop one byte past the destination if the WCOVE BMC receiver does not enforce the PD object-count limit in hardware. The existing FIXME flagged this as unverified.

Independently, regmapread() takes an unsigned int * and stores a full unsigned int at the destination. Passing the byte pointer msg + i means each iteration writes four bytes; the high three are zero (valbits is 8) and are normally overwritten by the next iteration, but the final iteration's high bytes are not. With RXBYTES == 30 the i == 29 iteration already writes three zero bytes past msg, which sits on the IRQ thread's stack in wcovetypecirq().

Clamp the loop to sizeof(struct pd_message) and read each register into a local before storing only its low byte, so the copy can never exceed the destination regardless of what RXINFO reports.