s390/mm: Remove folio handling for kernel faults in do_secure_storage_access()

Remove folio handling for secure storage access exceptions that happen
via the kernel mapping. Using folio_try_get() for exceptions via the
kernel mapping is racy: for example such an exception may happen on one
CPU, while a different CPU frees the corresponding page. Subsequently the
page can be part of a folio of different size, before the faulting CPU
executes folio_try_get(). This may lead to data corruption.

As of now this scenario does not seem to be possible, however with the
upcoming load_unaligned_zeropad() this is possible.

As a side effect PG_arch_1 is not cleared anymore for such faults via the
kernel mapping. However given that this bit is over-indicating it
shouldn't matter.

Tested-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Acked-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

0 files changed, 0 insertions, 0 deletions