i3c: master: svc: bound IBI payload to the requested max_payload_len

Overview

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.

Affected

• Linux >= dd3c52846d5954acd43f0e771689302f27dadc28 < 7c099b0b292a68d0ef558527945dbfb756fbf893
• Linux >= dd3c52846d5954acd43f0e771689302f27dadc28 < 7cc5ba756bc1cfffab9cb2695742f9f479dc73f7
• Linux >= dd3c52846d5954acd43f0e771689302f27dadc28 < 35aa6730b8c5626b879a4e893fe664f59bf07d7f
• Linux >= dd3c52846d5954acd43f0e771689302f27dadc28 < f296a0d5907bf88314dfda67245f7f69d1552470
• Linux >= dd3c52846d5954acd43f0e771689302f27dadc28 < 5697d779577e2786ff3348ae9b77020ac0cf0aab
• Linux >= dd3c52846d5954acd43f0e771689302f27dadc28 < aac3c5aababc7fb69d5bf5b0cc52d308574e3a8c
• Linux >= dd3c52846d5954acd43f0e771689302f27dadc28 < e2bda39d7f9f285ec803e200b5c1f17143d0b483
• Linux 5.12

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

Vendor advisories

• Red Hat VEX · Important · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · updated 2026-09-27 · vex