CVE-2026-98399

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

s390/ipl: Fix NULL deref in dump_reipl without re-IPL parm block

Unlike kdump, which passes the re-IPL parameter block through os_info,

the stand-alone dump passes it through the IPL parm block address and

checksum in lowcore.

Some IPL types, like HMC FTP boot or QEMU direct kernel boot, might not

provide an IPL parameter block. In this case reipl_type_init() selects

IPL_TYPE_UNKNOWN and reipl_block_actual remains NULL. Nevertheless,

dump_reipl_run() unconditionally dereferences it when preparing the

lowcore fields. This may happen to work by chance when address zero

contains readable lowcore data. A zero IPL parameter block address is

then stored in lowcore, causing the stand-alone dumper to enter disabled

wait after completing the dump.

Explicitly store a zero IPL parameter block address and checksum when no

re-IPL parameter block is available. This does not change the behavior:

the stand-alone dumper completes the dump and halts, while valid re-IPL

parameter blocks continue to be handled as before.