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    Subject[PATCH 4.4 85/86] s390/mm: Check for valid vma before zapping in gmap_discard
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Janosch Frank <frankja@linux.ibm.com>

    commit 1843abd03250115af6cec0892683e70cf2297c25 upstream.

    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: 1e133ab296f3 ("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>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/s390/mm/pgtable.c | 2 ++
    1 file changed, 2 insertions(+)

    --- a/arch/s390/mm/pgtable.c
    +++ b/arch/s390/mm/pgtable.c
    @@ -637,6 +637,8 @@ void gmap_discard(struct gmap *gmap, uns
    vmaddr |= gaddr & ~PMD_MASK;
    /* Find vma in the parent mm */
    vma = find_vma(gmap->mm, vmaddr);
    + if (!vma)
    + continue;
    size = min(to - gaddr, PMD_SIZE - (gaddr & ~PMD_MASK));
    zap_page_range(vma, vmaddr, size, NULL);
    }

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