s390/mm: fix BUG_ON in crst_table_upgrade
authorMartin Schwidefsky <schwidefsky@de.ibm.com>
Thu, 31 Aug 2017 11:18:22 +0000 (13:18 +0200)
committerMartin Schwidefsky <schwidefsky@de.ibm.com>
Thu, 31 Aug 2017 12:03:21 +0000 (14:03 +0200)
commit8ab867cb0806a8e195de161fd8883a0578d1d050
tree1181aefbc32ee92ad98c96f457581311f3229a3f
parent0b89ede629637c03b9a728fb08bfe6ed51de9be7
s390/mm: fix BUG_ON in crst_table_upgrade

A 31-bit compat process can force a BUG_ON in crst_table_upgrade
with specific, invalid mmap calls, e.g.

   mmap((void*) 0x7fff8000, 0x10000, 3, 32, -1, 0)

The arch_get_unmapped_area[_topdown] functions miss an if condition
in the decision to do a page table upgrade.

Fixes: 9b11c7912d00 ("s390/mm: simplify arch_get_unmapped_area[_topdown]")
Cc: <stable@vger.kernel.org> # v4.12+
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
arch/s390/mm/mmap.c