[Qemu-devel] [PATCH EMBARGOED 7/7] vmdk: check l1 size before opening image

[Fam Zheng <famz@redhat.com>]

L1 table size is calculated from capacity, granularity and l2 table
size. If capacity is too big or later two are too small, the L1 table
will be too big to allocate in memory. Limit it to a reasonable range.

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 block/vmdk.c               | 8 ++++++++
 tests/qemu-iotests/059     | 8 ++++++++
 tests/qemu-iotests/059.out | 6 ++++++
 3 files changed, 22 insertions(+)

diff --git a/block/vmdk.c b/block/vmdk.c
index e28bfc8..2114ef6 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -596,6 +596,14 @@ static int vmdk_open_vmdk4(BlockDriverState *bs,
     }
     l1_size = (le64_to_cpu(header.capacity) + l1_entry_sectors - 1)
                 / l1_entry_sectors;
+    if (l1_size > 512 * 1024 * 1024) {
+        /* although with big capacity and small l1_entry_sectors, we can get a
+         * big l1_size, we don't want unbounded value to allocate the table.
+         * Limit it to 512M, which is 16PB for default cluster and L2 table
+         * size */
+        error_report("L1 size too big");
+        return -EFBIG;
+    }
     if (le32_to_cpu(header.flags) & VMDK4_FLAG_RGD) {
         l1_backup_offset = le64_to_cpu(header.rgd_offset) << 9;
     }
diff --git a/tests/qemu-iotests/059 b/tests/qemu-iotests/059
index aa9eb57..e09e041 100755
--- a/tests/qemu-iotests/059
+++ b/tests/qemu-iotests/059
@@ -43,6 +43,7 @@ _supported_fmt vmdk
 _supported_proto generic
 _supported_os Linux
 
+capacity_offset=16
 granularity_offset=20
 grain_table_size_offset=44
 
@@ -58,6 +59,13 @@ _make_test_img 64M
 poke_file "$TEST_IMG" "$grain_table_size_offset" "\xff\xff\xff\xff"
 $QEMU_IO -c "read 0 512" $TEST_IMG 2>&1 | _filter_qemu_io | _filter_testdir
 
+echo "=== Testing too big L1 table size ==="
+echo
+_make_test_img 64M
+poke_file "$TEST_IMG" "$capacity_offset" "\xff\xff\xff\xff"
+poke_file "$TEST_IMG" "$grain_table_size_offset" "\x01\x00\x00\x00"
+$QEMU_IO -c "read 0 512" $TEST_IMG 2>&1 | _filter_qemu_io | _filter_testdir
+
 # success, all done
 echo "*** done"
 rm -f $seq.full
diff --git a/tests/qemu-iotests/059.out b/tests/qemu-iotests/059.out
index 583955f..9e715e5 100644
--- a/tests/qemu-iotests/059.out
+++ b/tests/qemu-iotests/059.out
@@ -11,4 +11,10 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
 L2 table size too big
 qemu-io: can't open device TEST_DIR/t.vmdk
 no file open, try 'help open'
+=== Testing too big L1 table size ===
+
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
+L1 size too big
+qemu-io: can't open device TEST_DIR/t.vmdk
+no file open, try 'help open'
 *** done
-- 
1.8.3.4