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

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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 3b9678472b ("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.

Fixes: 3b9678472b ("s390/ipl: correct kdump reipl block checksum calculation")
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
This commit is contained in:
Vasily Gorbik 2026-08-13 13:06:54 +02:00 committed by Heiko Carstens
parent f3c63b8cab
commit 7f91887111
1 changed files with 2 additions and 0 deletions
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2
arch/s390/kernel/ipl.c
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@ -1157,6 +1157,8 @@ static struct attribute_group reipl_nss_attr_group = {
void set_os_info_reipl_block(void)
{
if (!reipl_block_actual)
return;
os_info_entry_add_data(OS_INFO_REIPL_BLOCK, reipl_block_actual,
reipl_block_actual->hdr.len);
}