[Qemu-devel] [PATCH v2 2/5] qcow1: Check maximum cluster size

[Kevin Wolf <kwolf@redhat.com>]

Huge values for header.cluster_bits cause unbounded allocations (e.g.
for s->cluster_cache) and crash qemu this way. Less huge values may
survive those allocations, but can cause integer overflows later on.

The only cluster sizes that qemu can create are 4k (for standalone
images) and 512 (for images with backing files), so we can limit it
to 64k.

Cc: qemu-stable@nongnu.org
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/qcow.c               | 10 ++++++--
 tests/qemu-iotests/092     | 63 ++++++++++++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/092.out | 13 ++++++++++
 tests/qemu-iotests/group   |  1 +
 4 files changed, 85 insertions(+), 2 deletions(-)
 create mode 100755 tests/qemu-iotests/092
 create mode 100644 tests/qemu-iotests/092.out

diff --git a/block/qcow.c b/block/qcow.c
index 3684794..e60df23 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -128,11 +128,17 @@ static int qcow_open(BlockDriverState *bs, QDict *options, int flags,
         goto fail;
     }
 
-    if (header.size <= 1 || header.cluster_bits < 9) {
-        error_setg(errp, "invalid value in qcow header");
+    if (header.size <= 1) {
+        error_setg(errp, "Image size is too small (must be at least 2 bytes)");
         ret = -EINVAL;
         goto fail;
     }
+    if (header.cluster_bits < 9 || header.cluster_bits > 16) {
+        error_setg(errp, "Cluster size must be between 512 and 64k");
+        ret = -EINVAL;
+        goto fail;
+    }
+
     if (header.crypt_method > QCOW_CRYPT_AES) {
         error_setg(errp, "invalid encryption method in qcow header");
         ret = -EINVAL;
diff --git a/tests/qemu-iotests/092 b/tests/qemu-iotests/092
new file mode 100755
index 0000000..d060e6f
--- /dev/null
+++ b/tests/qemu-iotests/092
@@ -0,0 +1,63 @@
+#!/bin/bash
+#
+# qcow1 format input validation tests
+#
+# Copyright (C) 2014 Red Hat, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+# creator
+owner=kwolf@redhat.com
+
+seq=`basename $0`
+echo "QA output created by $seq"
+
+here=`pwd`
+tmp=/tmp/$$
+status=1	# failure is the default!
+
+_cleanup()
+{
+    rm -f $TEST_IMG.snap
+    _cleanup_test_img
+}
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+. ./common.rc
+. ./common.filter
+
+_supported_fmt qcow
+_supported_proto generic
+_supported_os Linux
+
+offset_cluster_bits=32
+
+echo
+echo "== Invalid cluster size =="
+_make_test_img 64M
+poke_file "$TEST_IMG" "$offset_cluster_bits" "\xff"
+{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
+poke_file "$TEST_IMG" "$offset_cluster_bits" "\x1f"
+{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
+poke_file "$TEST_IMG" "$offset_cluster_bits" "\x08"
+{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
+poke_file "$TEST_IMG" "$offset_cluster_bits" "\x11"
+{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
+
+# success, all done
+echo "*** done"
+rm -f $seq.full
+status=0
diff --git a/tests/qemu-iotests/092.out b/tests/qemu-iotests/092.out
new file mode 100644
index 0000000..8bf8158
--- /dev/null
+++ b/tests/qemu-iotests/092.out
@@ -0,0 +1,13 @@
+QA output created by 092
+
+== Invalid cluster size ==
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 
+qemu-io: can't open device TEST_DIR/t.qcow: Cluster size must be between 512 and 64k
+no file open, try 'help open'
+qemu-io: can't open device TEST_DIR/t.qcow: Cluster size must be between 512 and 64k
+no file open, try 'help open'
+qemu-io: can't open device TEST_DIR/t.qcow: Cluster size must be between 512 and 64k
+no file open, try 'help open'
+qemu-io: can't open device TEST_DIR/t.qcow: Cluster size must be between 512 and 64k
+no file open, try 'help open'
+*** done
diff --git a/tests/qemu-iotests/group b/tests/qemu-iotests/group
index 2988cfd..0f07440 100644
--- a/tests/qemu-iotests/group
+++ b/tests/qemu-iotests/group
@@ -98,3 +98,4 @@
 089 rw auto quick
 090 rw auto quick
 091 rw auto
+092 rw auto quick
-- 
1.8.3.1