From: David Hildenbrand david@redhat.com
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
--- arch/s390/mm/gmap.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
--- a/arch/s390/mm/gmap.c +++ b/arch/s390/mm/gmap.c @@ -759,14 +759,18 @@ static void gmap_call_notifier(struct gm static inline unsigned long *gmap_table_walk(struct gmap *gmap, unsigned long gaddr, int level) { + const int asce_type = gmap->asce & _ASCE_TYPE_MASK; unsigned long *table;
if ((gmap->asce & _ASCE_TYPE_MASK) + 4 < (level * 4)) return NULL; if (gmap_is_shadow(gmap) && gmap->removed) return NULL; - if (gaddr & (-1UL << (31 + ((gmap->asce & _ASCE_TYPE_MASK) >> 2)*11))) + + if (asce_type != _ASCE_TYPE_REGION1 && + gaddr & (-1UL << (31 + (asce_type >> 2) * 11))) return NULL; + table = gmap->table; switch (gmap->asce & _ASCE_TYPE_MASK) { case _ASCE_TYPE_REGION1: