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From 0f9e33b29b76a647c903753a0758b9c85e75d73a Mon Sep 17 00:00:00 2001
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From: Kevin Wolf <kwolf@redhat.com>
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Date: Tue, 25 Mar 2014 14:23:29 +0100
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Subject: [PATCH 22/49] qcow2: Check refcount table size (CVE-2014-0144)
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RH-Author: Kevin Wolf <kwolf@redhat.com>
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Message-id: <1395753835-7591-23-git-send-email-kwolf@redhat.com>
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Patchwork-id: n/a
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O-Subject: [virt-devel] [EMBARGOED RHEL-7.0 qemu-kvm PATCH 22/48] qcow2: Check refcount table size (CVE-2014-0144)
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Bugzilla: 1079455
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RH-Acked-by: Jeff Cody <jcody@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1079455
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Upstream status: Embargoed
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Limit the in-memory reference count table size to 8 MB, it's enough in
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practice. This fixes an unbounded allocation as well as a buffer
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overflow in qcow2_refcount_init().
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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---
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block/qcow2-refcount.c | 4 +++-
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block/qcow2.c | 9 +++++++++
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tests/qemu-iotests/080 | 10 ++++++++++
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tests/qemu-iotests/080.out | 7 +++++++
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4 files changed, 29 insertions(+), 1 deletions(-)
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diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
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index 09c638f..13ea5f7 100644
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--- a/block/qcow2-refcount.c
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+++ b/block/qcow2-refcount.c
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@@ -40,8 +40,10 @@ static int QEMU_WARN_UNUSED_RESULT update_refcount(BlockDriverState *bs,
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int qcow2_refcount_init(BlockDriverState *bs)
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{
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BDRVQcowState *s = bs->opaque;
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- int ret, refcount_table_size2, i;
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+ unsigned int refcount_table_size2, i;
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+ int ret;
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+ assert(s->refcount_table_size <= INT_MAX / sizeof(uint64_t));
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refcount_table_size2 = s->refcount_table_size * sizeof(uint64_t);
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s->refcount_table = g_malloc(refcount_table_size2);
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if (s->refcount_table_size > 0) {
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diff --git a/block/qcow2.c b/block/qcow2.c
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index 5568cf9..a7780ac 100644
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--- a/block/qcow2.c
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+++ b/block/qcow2.c
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@@ -576,10 +576,19 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
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s->csize_shift = (62 - (s->cluster_bits - 8));
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s->csize_mask = (1 << (s->cluster_bits - 8)) - 1;
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s->cluster_offset_mask = (1LL << s->csize_shift) - 1;
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+
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s->refcount_table_offset = header.refcount_table_offset;
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s->refcount_table_size =
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header.refcount_table_clusters << (s->cluster_bits - 3);
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+ if (header.refcount_table_clusters > (0x800000 >> s->cluster_bits)) {
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+ /* 8 MB refcount table is enough for 2 PB images at 64k cluster size
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+ * (128 GB for 512 byte clusters, 2 EB for 2 MB clusters) */
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+ error_setg(errp, "Reference count table too large");
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+ ret = -EINVAL;
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+ goto fail;
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+ }
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+
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s->snapshots_offset = header.snapshots_offset;
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s->nb_snapshots = header.nb_snapshots;
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diff --git a/tests/qemu-iotests/080 b/tests/qemu-iotests/080
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index 6d588dd..6179e05 100755
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--- a/tests/qemu-iotests/080
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+++ b/tests/qemu-iotests/080
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@@ -45,6 +45,7 @@ _supported_os Linux
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header_size=104
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offset_backing_file_offset=8
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+offset_refcount_table_clusters=56
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offset_header_size=100
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offset_ext_magic=$header_size
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offset_ext_size=$((header_size + 4))
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@@ -67,6 +68,15 @@ poke_file "$TEST_IMG" "$offset_ext_size" "\x7f\xff\xff\xff"
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poke_file "$TEST_IMG" "$offset_backing_file_offset" "\x00\x00\x00\x00\x00\x00\x00\x00"
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{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
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+echo
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+echo "== Huge refcount table size =="
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+_make_test_img 64M
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+poke_file "$TEST_IMG" "$offset_refcount_table_clusters" "\xff\xff\xff\xff"
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+{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
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+poke_file "$TEST_IMG" "$offset_refcount_table_clusters" "\x00\x02\x00\x01"
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+{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
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+
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+
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# success, all done
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echo "*** done"
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rm -f $seq.full
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diff --git a/tests/qemu-iotests/080.out b/tests/qemu-iotests/080.out
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index 48c40aa..6fef6d9 100644
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--- a/tests/qemu-iotests/080.out
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+++ b/tests/qemu-iotests/080.out
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@@ -13,4 +13,11 @@ qemu-io: can't open device TEST_DIR/t.qcow2: Invalid backing file offset
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no file open, try 'help open'
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qemu-io: can't open device TEST_DIR/t.qcow2: Header extension too large
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no file open, try 'help open'
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+
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+== Huge refcount table size ==
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+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
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+qemu-io: can't open device TEST_DIR/t.qcow2: Reference count table too large
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+no file open, try 'help open'
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+qemu-io: can't open device TEST_DIR/t.qcow2: Reference count table too large
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+no file open, try 'help open'
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*** done
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--
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1.7.1
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