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s390/mm: Check for valid vma before zapping in gmap_discard

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Userspace could have munmapped the area before doing unmapping from
the gmap. This would leave us with a valid vmaddr, but an invalid vma
from which we would try to zap memory.

Let's check before using the vma.

Fixes: 1e133ab296 ("s390/mm: split arch/s390/mm/pgtable.c")
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Message-Id: <20180816082432.78828-1-frankja@linux.ibm.com>
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
This commit is contained in:
Janosch Frank 2018-08-16 09:02:31 +01:00
parent df88f3181f
commit 1843abd032
1 changed files with 3 additions and 1 deletions
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4
arch/s390/mm/gmap.c
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@ -708,11 +708,13 @@ void gmap_discard(struct gmap *gmap, unsigned long from, unsigned long to)
vmaddr |= gaddr & ~PMD_MASK;
/* Find vma in the parent mm */
vma = find_vma(gmap->mm, vmaddr);
if (!vma)
continue;
/*
* We do not discard pages that are backed by
* hugetlbfs, so we don't have to refault them.
*/
if (vma && is_vm_hugetlb_page(vma))
if (is_vm_hugetlb_page(vma))
continue;
size = min(to - gaddr, PMD_SIZE - (gaddr & ~PMD_MASK));
zap_page_range(vma, vmaddr, size);