From: David Hildenbrand david@redhat.com
[ Upstream commit b159f94c86b43cf7e73e654bc527255b1f4eafc4 ]
... otherwise we will try unlocking a spinlock that was never locked via a garbage pointer.
At the time we reach this code path, we usually successfully looked up a PGSTE already; however, evil user space could have manipulated the VMA layout in the meantime and triggered removal of the page table.
Fixes: 1e133ab296f3 ("s390/mm: split arch/s390/mm/pgtable.c") Signed-off-by: David Hildenbrand david@redhat.com Reviewed-by: Claudio Imbrenda imbrenda@linux.ibm.com Acked-by: Heiko Carstens hca@linux.ibm.com Link: https://lore.kernel.org/r/20210909162248.14969-3-david@redhat.com Signed-off-by: Christian Borntraeger borntraeger@de.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/s390/mm/gmap.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
--- a/arch/s390/mm/gmap.c +++ b/arch/s390/mm/gmap.c @@ -662,9 +662,10 @@ void __gmap_zap(struct gmap *gmap, unsig vmaddr |= gaddr & ~PMD_MASK; /* Get pointer to the page table entry */ ptep = get_locked_pte(gmap->mm, vmaddr, &ptl); - if (likely(ptep)) + if (likely(ptep)) { ptep_zap_unused(gmap->mm, vmaddr, ptep, 0); - pte_unmap_unlock(ptep, ptl); + pte_unmap_unlock(ptep, ptl); + } } } EXPORT_SYMBOL_GPL(__gmap_zap);