Bug 2552222 (CVE-2026-98399)

Summary: CVE-2026-98399 kernel: s390/ipl: Fix NULL deref in dump_reipl without re-IPL parm block
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: low Docs Contact:
Priority: low    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel. On s390 (IBM Z) systems booted without an Initial Program Load (IPL) parameter block, such as during direct kernel boot, the kernel does not verify the parameter block before dereferencing it during dump operations. A local privileged user could trigger this condition during system shutdown or dump preparation, causing a null pointer dereference. This issue results in a kernel crash, leading to a denial of service (DoS).
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Description OSIDB Bzimport 2026-10-14 13:50:22 UTC 
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.