tree 1717b3c01987f7789e8071d7640ac1a758e08fb8
parent deecbb365568235e27bcbae39cbfae93a283bb00
author David Hildenbrand <david@redhat.com> 1585927846 +0200
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1587113327 +0200

KVM: s390: vsie: Fix region 1 ASCE sanity shadow address checks

commit a1d032a49522cb5368e5dfb945a85899b4c74f65 upstream.

In case we have a region 1 the following calculation
(31 + ((gmap->asce & _ASCE_TYPE_MASK) >> 2)*11)
results in 64. As shifts beyond the size are undefined the compiler is
free to use instructions like sllg. sllg will only use 6 bits of the
shift value (here 64) resulting in no shift at all. That means that ALL
addresses will be rejected.

The can result in endless loops, e.g. when prefix cannot get mapped.

Fixes: 4be130a08420 ("s390/mm: add shadow gmap support")
Tested-by: Janosch Frank <frankja@linux.ibm.com>
Reported-by: Janosch Frank <frankja@linux.ibm.com>
Cc: <stable@vger.kernel.org> # v4.8+
Signed-off-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20200403153050.20569-2-david@redhat.com
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
[borntraeger@de.ibm.com: fix patch description, remove WARN_ON_ONCE]
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>