CVE-2026-80951

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

i3c: master: svc: bound IBI payload to the requested max payload len

svc i3c master handle ibi() reads the IBI payload from the RX FIFO into the IBI slot. The loop is bounded by the hardware FIFO size (SVC I3C FIFO SIZE), not by the slot size.

slot->data points into the IBI pool, which i3c generic ibi alloc pool() sizes at max payload len per slot. svc i3c master request ibi() only rejects a max payload len larger than SVC I3C FIFO SIZE, so a driver can request a smaller one. mctp-i3c requests 1. Each readsb() then copies the controller RXCOUNT bytes (up to 31) with no check against the slot size. A device that sends more bytes than the slot holds writes past slot->data, an out-of-bounds write into the IBI pool.

Bound the loop by dev->ibi->max payload len and clamp each read to the space left in the slot, the same way dw-i3c does. A device can still send more than the requested payload. Flush the leftover bytes from the RX FIFO so they do not leak into the next transfer.