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powerpc/rtas: Allow ibm,platform-dump RTAS call with null buffer address

Mamatha Inamdar requested to merge mainamdar/centos-stream-9:bz2095499 into main

Bugzilla: https://bugzilla.redhat.com/2095499

BI:https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=49053882

Tested: Verified Brew build test kernel RPMs and confirmed issue is resovled

commit 7bc08056a6dabc3a1442216daf527edf61ac24b6 Author: Andrew Donnellan ajd@linux.ibm.com Date: Tue Jun 14 23:49:52 2022 +1000

powerpc/rtas: Allow ibm,platform-dump RTAS call with null buffer address

Add a special case to block_rtas_call() to allow the ibm,platform-dump RTAS
call through the RTAS filter if the buffer address is 0.

According to PAPR, ibm,platform-dump is called with a null buffer address
to notify the platform firmware that processing of a particular dump is
finished.

Without this, on a pseries machine with CONFIG_PPC_RTAS_FILTER enabled, an
application such as rtas_errd that is attempting to retrieve a dump will
encounter an error at the end of the retrieval process.

Fixes: bd59380c5ba4 ("powerpc/rtas: Restrict RTAS requests from userspace")
Cc: stable@vger.kernel.org
Reported-by: Sathvika Vasireddy <sathvika@linux.ibm.com>
Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
Reviewed-by: Tyrel Datwyler <tyreld@linux.ibm.com>
Reviewed-by: Nathan Lynch <nathanl@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220614134952.156010-1-ajd@linux.ibm.com

Signed-off-by: Mamatha Inamdar minamdar@redhat.com

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