qcow2: Validate active L1 table offset and size (CVE-2014-0144)

This avoids an unbounded allocation.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

block/qcow2.c

@@ -642,6 +642,13 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
     s->nb_snapshots = header.nb_snapshots;
 
     /* read the level 1 table */
+    if (header.l1_size > 0x2000000) {
+        /* 32 MB L1 table is enough for 2 PB images at 64k cluster size
+         * (128 GB for 512 byte clusters, 2 EB for 2 MB clusters) */
+        error_setg(errp, "Active L1 table too large");
+        ret = -EFBIG;
+        goto fail;
+    }
     s->l1_size = header.l1_size;
 
     l1_vm_state_index = size_to_l1(s, header.size);
@@ -659,7 +666,16 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
         ret = -EINVAL;
         goto fail;
     }
+
+    ret = validate_table_offset(bs, header.l1_table_offset,
+                                header.l1_size, sizeof(uint64_t));
+    if (ret < 0) {
+        error_setg(errp, "Invalid L1 table offset");
+        goto fail;
+    }
     s->l1_table_offset = header.l1_table_offset;
+
+
     if (s->l1_size > 0) {
         s->l1_table = g_malloc0(
             align_offset(s->l1_size * sizeof(uint64_t), 512));

tests/qemu-iotests/080

@@ -45,6 +45,8 @@ _supported_os Linux
 header_size=104
 
 offset_backing_file_offset=8
+offset_l1_size=36
+offset_l1_table_offset=40
 offset_refcount_table_offset=48
 offset_refcount_table_clusters=56
 offset_nb_snapshots=60
@@ -117,6 +119,22 @@ poke_file "$TEST_IMG" "$offset_nb_snapshots" "\x00\x01\x00\x00"
 { $QEMU_IMG snapshot -c test $TEST_IMG; } 2>&1 | _filter_testdir
 { $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
 
+echo
+echo "== Invalid L1 table =="
+_make_test_img 64M
+poke_file "$TEST_IMG" "$offset_l1_size" "\xff\xff\xff\xff"
+{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
+poke_file "$TEST_IMG" "$offset_l1_size" "\x7f\xff\xff\xff"
+{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
+
+poke_file "$TEST_IMG" "$offset_l1_table_offset" "\x7f\xff\xff\xff\xff\xff\x00\x00"
+poke_file "$TEST_IMG" "$offset_l1_size" "\x00\x00\xff\xff"
+{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
+
+poke_file "$TEST_IMG" "$offset_l1_table_offset" "\x12\x34\x56\x78\x90\xab\xcd\xef"
+poke_file "$TEST_IMG" "$offset_l1_size" "\x00\x00\x00\x01"
+{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
+
 # success, all done
 echo "*** done"
 rm -f $seq.full

tests/qemu-iotests/080.out

@@ -47,4 +47,15 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
 qemu-img: Could not create snapshot 'test': -27 (File too large)
 read 512/512 bytes at offset 0
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+== Invalid L1 table ==
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 
+qemu-io: can't open device TEST_DIR/t.qcow2: Active L1 table too large
+no file open, try 'help open'
+qemu-io: can't open device TEST_DIR/t.qcow2: Active L1 table too large
+no file open, try 'help open'
+qemu-io: can't open device TEST_DIR/t.qcow2: Invalid L1 table offset
+no file open, try 'help open'
+qemu-io: can't open device TEST_DIR/t.qcow2: Invalid L1 table offset
+no file open, try 'help open'
 *** done