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.