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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Janosch Frank <frankja@linux.ibm.com>,
        David Hildenbrand <david@redhat.com>,
        Dan Carpenter <dan.carpenter@oracle.com>
Subject: [PATCH 4.4 85/86] s390/mm: Check for valid vma before zapping in gmap_discard
Date:   Thu, 29 Nov 2018 15:12:50 +0100
Message-Id: <20181129140116.504805310@linuxfoundation.org>
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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);
 	}