[Qemu-devel] [PATCH 046/108] qcow1: Check maximum cluster size

[Michael Roth]

From: Kevin Wolf <address@hidden>

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: address@hidden
Signed-off-by: Kevin Wolf <address@hidden>
Reviewed-by: Benoit Canet <address@hidden>
(cherry picked from commit 7159a45b2bf2dcb9f49f1e27d1d3d135a0247a2f)

Conflicts:
        tests/qemu-iotests/group

*removed context lines for tests not present in v2.0.0

Signed-off-by: Michael Roth <address@hidden>
---
 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 9018f44..26bb923 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -127,11 +127,17 @@ 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
address@hidden
+
+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 864643d..a4e601b 100644
--- a/tests/qemu-iotests/group
+++ b/tests/qemu-iotests/group
@@ -95,3 +95,4 @@
 086 rw auto quick
 087 rw auto
 088 rw auto
+092 rw auto quick
-- 
1.9.1