CVE-2026-46064

Description

In the Linux kernel, the following vulnerability has been resolved: ibmasm: fix heap over-read in ibmasm_send_i2o_message() The ibmasm_send_i2o_message() function uses get_dot_command_size() to compute the byte count for memcpy_toio(), but this value is derived from user-controlled fields in the dot_command_header (command_size: u8, data_size: u16) and is never validated against the actual allocation size. A root user can write a small buffer with inflated header fields, causing memcpy_toio() to read up to ~65 KB past the end of the allocation into adjacent kernel heap, which is then forwarded to the service processor over MMIO. Silently clamping the copy size is not sufficient: if the header fields claim a larger size than the buffer, the SP receives a dot command whose own header is inconsistent with the I2O message length, which can cause the SP to desynchronize. Reject such commands outright by returning failure. Validate command_size before calling get_mfa_inbound() to avoid leaking an I2O message frame: reading INBOUND_QUEUE_PORT dequeues a hardware frame from the controller's free pool, and returning without a corresponding set_mfa_inbound() call would permanently exhaust it. Additionally, clamp command_size to I2O_COMMAND_SIZE before the memcpy_toio() so the MMIO write stays within the I2O message frame, consistent with the clamping already performed by outgoing_message_size() for the header field.

Predictions

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

References

• https://git.kernel.org/stable/c/fd19eb1c75047a4ed4e855f56cafd704dc3914e0
• https://git.kernel.org/stable/c/fe31722b0194ff76bf8b461e8bf97a2081147787
• https://git.kernel.org/stable/c/c1c2417c60dbdca5ebb00462f21ee71c2d7f7083
• https://git.kernel.org/stable/c/9e8f6c9d4ecddda2f28baa1678340286cff3969c
• https://git.kernel.org/stable/c/9aad71144fa3682cca3837a06c8623016790e7ec
• https://security-tracker.debian.org/tracker/CVE-2026-46064