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

Andrew Donnellan [off-list ref] writes:

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 <redacted>
Signed-off-by: Andrew Donnellan <redacted>

I agree this allows ibm,platform-dump to work without weakening the
filter for other calls. Thanks.

Reviewed-by: Nathan Lynch <redacted>