qcow2: Validate snapshot table offset/size (CVE-2014-0144)

This avoid unbounded memory allocation and fixes a potential buffer
overflow on 32 bit hosts.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Kevin Wolf 2014-03-26 13:05:45 +01:00 committed by Stefan Hajnoczi
parent 8c7de28305
commit ce48f2f441
5 changed files with 91 additions and 26 deletions

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@ -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;
@ -357,6 +332,10 @@ 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 */

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@ -623,6 +623,21 @@ 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;

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@ -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 (1ULL << 63)
@ -97,6 +98,32 @@ typedef struct QCowHeader {
uint32_t header_length;
} QEMU_PACKED 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;

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@ -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

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@ -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