The Linux kernel s390/dasd driver had a flaw in dasd_int_handler() where an NRF read of an unallocated ESE track was completed as successful regardless of errors from ese_read(). Specifically, dasd_eckd_ese_read() could return an error before zeroing the destination buffer, leaving stale or uninitialized memory in the buffer. Despite this, the request was marked DASD_CQR_SUCCESS, causing the block layer to receive invalid data. The vulnerability was fixed by adding proper error checking of ese_read() and failing the request if an error occurs.

The vulnerability could cause the block layer to receive stale or uninitialized memory instead of zeroed data when an ESE read fails. This could potentially lead to data integrity issues or leakage of residual memory contents. No information about exploitation or active attacks is available.

A fix has been applied to the Linux kernel to properly check the return value of ese_read() and fail the request on error instead of marking it successful. Users should update to the fixed kernel version once available. No additional mitigation is indicated.