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From 0f9e33b29b76a647c903753a0758b9c85e75d73a Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Tue, 25 Mar 2014 14:23:29 +0100
Subject: [PATCH 22/49] qcow2: Check refcount table size (CVE-2014-0144)
RH-Author: Kevin Wolf <kwolf@redhat.com>
Message-id: <1395753835-7591-23-git-send-email-kwolf@redhat.com>
Patchwork-id: n/a
O-Subject: [virt-devel] [EMBARGOED RHEL-7.0 qemu-kvm PATCH 22/48] qcow2: Check refcount table size (CVE-2014-0144)
Bugzilla: 1079455
RH-Acked-by: Jeff Cody <jcody@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1079455
Upstream status: Embargoed
Limit the in-memory reference count table size to 8 MB, it's enough in
practice. This fixes an unbounded allocation as well as a buffer
overflow in qcow2_refcount_init().
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
block/qcow2-refcount.c | 4 +++-
block/qcow2.c | 9 +++++++++
tests/qemu-iotests/080 | 10 ++++++++++
tests/qemu-iotests/080.out | 7 +++++++
4 files changed, 29 insertions(+), 1 deletions(-)
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 09c638f..13ea5f7 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -40,8 +40,10 @@ static int QEMU_WARN_UNUSED_RESULT update_refcount(BlockDriverState *bs,
int qcow2_refcount_init(BlockDriverState *bs)
{
BDRVQcowState *s = bs->opaque;
- int ret, refcount_table_size2, i;
+ unsigned int refcount_table_size2, i;
+ int ret;
+ assert(s->refcount_table_size <= INT_MAX / sizeof(uint64_t));
refcount_table_size2 = s->refcount_table_size * sizeof(uint64_t);
s->refcount_table = g_malloc(refcount_table_size2);
if (s->refcount_table_size > 0) {
diff --git a/block/qcow2.c b/block/qcow2.c
index 5568cf9..a7780ac 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -576,10 +576,19 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
s->csize_shift = (62 - (s->cluster_bits - 8));
s->csize_mask = (1 << (s->cluster_bits - 8)) - 1;
s->cluster_offset_mask = (1LL << s->csize_shift) - 1;
+
s->refcount_table_offset = header.refcount_table_offset;
s->refcount_table_size =
header.refcount_table_clusters << (s->cluster_bits - 3);
+ if (header.refcount_table_clusters > (0x800000 >> s->cluster_bits)) {
+ /* 8 MB refcount 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, "Reference count table too large");
+ ret = -EINVAL;
+ goto fail;
+ }
+
s->snapshots_offset = header.snapshots_offset;
s->nb_snapshots = header.nb_snapshots;
diff --git a/tests/qemu-iotests/080 b/tests/qemu-iotests/080
index 6d588dd..6179e05 100755
--- a/tests/qemu-iotests/080
+++ b/tests/qemu-iotests/080
@@ -45,6 +45,7 @@ _supported_os Linux
header_size=104
offset_backing_file_offset=8
+offset_refcount_table_clusters=56
offset_header_size=100
offset_ext_magic=$header_size
offset_ext_size=$((header_size + 4))
@@ -67,6 +68,15 @@ poke_file "$TEST_IMG" "$offset_ext_size" "\x7f\xff\xff\xff"
poke_file "$TEST_IMG" "$offset_backing_file_offset" "\x00\x00\x00\x00\x00\x00\x00\x00"
{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
+echo
+echo "== Huge refcount table size =="
+_make_test_img 64M
+poke_file "$TEST_IMG" "$offset_refcount_table_clusters" "\xff\xff\xff\xff"
+{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
+poke_file "$TEST_IMG" "$offset_refcount_table_clusters" "\x00\x02\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
diff --git a/tests/qemu-iotests/080.out b/tests/qemu-iotests/080.out
index 48c40aa..6fef6d9 100644
--- a/tests/qemu-iotests/080.out
+++ b/tests/qemu-iotests/080.out
@@ -13,4 +13,11 @@ qemu-io: can't open device TEST_DIR/t.qcow2: Invalid backing file offset
no file open, try 'help open'
qemu-io: can't open device TEST_DIR/t.qcow2: Header extension too large
no file open, try 'help open'
+
+== Huge refcount table size ==
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
+qemu-io: can't open device TEST_DIR/t.qcow2: Reference count table too large
+no file open, try 'help open'
+qemu-io: can't open device TEST_DIR/t.qcow2: Reference count table too large
+no file open, try 'help open'
*** done
--
1.7.1