CVE-2026-64085

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

hwmon: (pmbus/adm1266) bounce blackbox records through a protocol-sized buffer

adm1266pmbusblock_xfer() copies the device-supplied block payload into the caller-provided buffer using the device-supplied length:

memcpy(data_r, &msgs[1].buf[1], msgs[1].buf[0]);

The helper does not know how large datar is and trusts the device to return at most one record's worth of bytes. adm1266nvmemreadblackbox() violates that contract: it advances readbuff inside data->devmem in ADM1266BLACKBOXSIZE (64-byte) strides while the helper is willing to write up to ADM1266PMBUSBLOCKMAX (255) bytes. A device that returns more than 64 bytes on the trailing record (readbuff offset 1984 in the 2048-byte devmem allocation) overflows devmem by up to 191 bytes before the post-call

if (ret != ADM1266_BLACKBOX_SIZE)
    return -EIO;

can reject the response.

Contain the fix in the caller without changing the helper signature: read each record into a 255-byte local bounce buffer that matches the helper's maximum output, validate the returned length, and only then copy exactly ADM1266BLACKBOXSIZE bytes into the dev_mem slot.