From 2318681bf850996a3e9c682ca3290aa9f05fd15c Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Tue, 25 Mar 2014 14:23:31 +0100
Subject: [PATCH 24/49] qcow2: Validate snapshot table offset/size (CVE-2014-0144)
RH-Author: Kevin Wolf <kwolf@redhat.com>
Message-id: <1395753835-7591-25-git-send-email-kwolf@redhat.com>
Patchwork-id: n/a
O-Subject: [virt-devel] [EMBARGOED RHEL-7.0 qemu-kvm PATCH 24/48] qcow2: Validate snapshot table offset/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
This avoid unbounded memory allocation and fixes a potential buffer
overflow on 32 bit hosts.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
block/qcow2-snapshot.c | 29 ++++-------------------------
block/qcow2.c | 15 +++++++++++++++
block/qcow2.h | 29 ++++++++++++++++++++++++++++-
tests/qemu-iotests/080 | 27 +++++++++++++++++++++++++++
tests/qemu-iotests/080.out | 17 +++++++++++++++++
5 files changed, 91 insertions(+), 26 deletions(-)
diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
index aa88c51..5d73506 100644
--- a/block/qcow2-snapshot.c
+++ b/block/qcow2-snapshot.c
@@ -26,31 +26,6 @@
#include "block/block_int.h"
#include "block/qcow2.h"
-typedef struct QEMU_PACKED QCowSnapshotHeader {
- /* header is 8 byte aligned */
- uint64_t l1_table_offset;
-
- uint32_t l1_size;
- uint16_t id_str_size;
- uint16_t name_size;
-
- uint32_t date_sec;
- uint32_t date_nsec;
-
- uint64_t vm_clock_nsec;
-
- uint32_t vm_state_size;
- uint32_t extra_data_size; /* for extension */
- /* extra data follows */
- /* id_str follows */
- /* name follows */
-} QCowSnapshotHeader;
-
-typedef struct QEMU_PACKED QCowSnapshotExtraData {
- uint64_t vm_state_size_large;
- uint64_t disk_size;
-} QCowSnapshotExtraData;
-
void qcow2_free_snapshots(BlockDriverState *bs)
{
BDRVQcowState *s = bs->opaque;
@@ -334,6 +309,10 @@ int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
uint64_t *l1_table = NULL;
int64_t l1_table_offset;
+ if (s->nb_snapshots >= QCOW_MAX_SNAPSHOTS) {
+ return -EFBIG;
+ }
+
memset(sn, 0, sizeof(*sn));
/* Generate an ID if it wasn't passed */
diff --git a/block/qcow2.c b/block/qcow2.c
index 5513fac..8c74dea 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -622,6 +622,21 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
goto fail;
}
+ /* Snapshot table offset/length */
+ if (header.nb_snapshots > QCOW_MAX_SNAPSHOTS) {
+ error_setg(errp, "Too many snapshots");
+ ret = -EINVAL;
+ goto fail;
+ }
+
+ ret = validate_table_offset(bs, header.snapshots_offset,
+ header.nb_snapshots,
+ sizeof(QCowSnapshotHeader));
+ if (ret < 0) {
+ error_setg(errp, "Invalid snapshot table offset");
+ goto fail;
+ }
+
s->snapshots_offset = header.snapshots_offset;
s->nb_snapshots = header.nb_snapshots;
diff --git a/block/qcow2.h b/block/qcow2.h
index 4a653c5..5efc96e 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -38,6 +38,7 @@
#define QCOW_CRYPT_AES 1
#define QCOW_MAX_CRYPT_CLUSTERS 32
+#define QCOW_MAX_SNAPSHOTS 65536
/* indicate that the refcount of the referenced cluster is exactly one. */
#define QCOW_OFLAG_COPIED (1LL << 63)
@@ -97,6 +98,32 @@ typedef struct QCowHeader {
uint32_t header_length;
} QCowHeader;
+typedef struct QEMU_PACKED QCowSnapshotHeader {
+ /* header is 8 byte aligned */
+ uint64_t l1_table_offset;
+
+ uint32_t l1_size;
+ uint16_t id_str_size;
+ uint16_t name_size;
+
+ uint32_t date_sec;
+ uint32_t date_nsec;
+
+ uint64_t vm_clock_nsec;
+
+ uint32_t vm_state_size;
+ uint32_t extra_data_size; /* for extension */
+ /* extra data follows */
+ /* id_str follows */
+ /* name follows */
+} QCowSnapshotHeader;
+
+typedef struct QEMU_PACKED QCowSnapshotExtraData {
+ uint64_t vm_state_size_large;
+ uint64_t disk_size;
+} QCowSnapshotExtraData;
+
+
typedef struct QCowSnapshot {
uint64_t l1_table_offset;
uint32_t l1_size;
@@ -202,7 +229,7 @@ typedef struct BDRVQcowState {
AES_KEY aes_decrypt_key;
uint64_t snapshots_offset;
int snapshots_size;
- int nb_snapshots;
+ unsigned int nb_snapshots;
QCowSnapshot *snapshots;
int flags;
diff --git a/tests/qemu-iotests/080 b/tests/qemu-iotests/080
index f58ac73..8a8b460 100755
--- a/tests/qemu-iotests/080
+++ b/tests/qemu-iotests/080
@@ -47,6 +47,8 @@ header_size=104
offset_backing_file_offset=8
offset_refcount_table_offset=48
offset_refcount_table_clusters=56
+offset_nb_snapshots=60
+offset_snapshots_offset=64
offset_header_size=100
offset_ext_magic=$header_size
offset_ext_size=$((header_size + 4))
@@ -90,6 +92,31 @@ poke_file "$TEST_IMG" "$offset_refcount_table_offset" "\xff\xff\xff\xff\xff\xff\
poke_file "$TEST_IMG" "$offset_refcount_table_clusters" "\x00\x00\x00\x7f"
{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
+echo
+echo "== Invalid snapshot table =="
+_make_test_img 64M
+poke_file "$TEST_IMG" "$offset_nb_snapshots" "\xff\xff\xff\xff"
+{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
+poke_file "$TEST_IMG" "$offset_nb_snapshots" "\x7f\xff\xff\xff"
+{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
+
+poke_file "$TEST_IMG" "$offset_snapshots_offset" "\xff\xff\xff\xff\xff\xff\x00\x00"
+poke_file "$TEST_IMG" "$offset_nb_snapshots" "\x00\x00\xff\xff"
+{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
+
+poke_file "$TEST_IMG" "$offset_snapshots_offset" "\x12\x34\x56\x78\x90\xab\xcd\xef"
+poke_file "$TEST_IMG" "$offset_nb_snapshots" "\x00\x00\x00\x00"
+{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
+
+echo
+echo "== Hitting snapshot table size limit =="
+_make_test_img 64M
+# Put the refcount table in a more or less safe place (16 MB)
+poke_file "$TEST_IMG" "$offset_snapshots_offset" "\x00\x00\x00\x00\x01\x00\x00\x00"
+poke_file "$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
+
# success, all done
echo "*** done"
rm -f $seq.full
diff --git a/tests/qemu-iotests/080.out b/tests/qemu-iotests/080.out
index f919b58..b06f47f 100644
--- a/tests/qemu-iotests/080.out
+++ b/tests/qemu-iotests/080.out
@@ -30,4 +30,21 @@ no file open, try 'help open'
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
qemu-io: can't open device TEST_DIR/t.qcow2: Invalid reference count table offset
no file open, try 'help open'
+
+== Invalid snapshot table ==
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
+qemu-io: can't open device TEST_DIR/t.qcow2: Too many snapshots
+no file open, try 'help open'
+qemu-io: can't open device TEST_DIR/t.qcow2: Too many snapshots
+no file open, try 'help open'
+qemu-io: can't open device TEST_DIR/t.qcow2: Invalid snapshot table offset
+no file open, try 'help open'
+qemu-io: can't open device TEST_DIR/t.qcow2: Invalid snapshot table offset
+no file open, try 'help open'
+
+== Hitting snapshot table size limit ==
+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)
*** done
--
1.7.1