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

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In the Linux kernel, the following vulnerability has been resolved: s390/ipl: Fix NULL deref in kdump without re-IPL parm block 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. kdump passes the re-IPL parameter block to the dump kernel through os_info. Before commit 3b9678472bab ("s390/ipl: correct kdump reipl block checksum calculation"), the os_info entry was added only for IPL types which initialized reipl_block_actual. That commit moved the os_info update to machine_crash_shutdown(), making it unconditional. As a result, set_os_info_reipl_block() dereferences reipl_block_actual for IPL_TYPE_UNKNOWN. This may happen to work by chance when address zero contains readable lowcore data and the resulting empty os_info entry is ignored by the dump kernel. Skip the os_info update when no re-IPL parameter block is available. Kdump then collect the dump and reboot without setting re-IPL parameter block.

Source published

14 Oct 2026 13:26:00 UTC

Source modified

19 Oct 2026 09:18:53 UTC

Observed here

23 Oct 2026 15:48:27 UTC

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