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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
Stefan Hajnoczi
parent
8c7de28305
commit
ce48f2f441
@ -26,31 +26,6 @@
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#include "block/block_int.h"
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#include "block/qcow2.h"
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typedef struct QEMU_PACKED QCowSnapshotHeader {
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/* header is 8 byte aligned */
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uint64_t l1_table_offset;
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uint32_t l1_size;
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uint16_t id_str_size;
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uint16_t name_size;
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uint32_t date_sec;
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uint32_t date_nsec;
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uint64_t vm_clock_nsec;
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uint32_t vm_state_size;
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uint32_t extra_data_size; /* for extension */
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/* extra data follows */
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/* id_str follows */
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/* name follows */
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} QCowSnapshotHeader;
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typedef struct QEMU_PACKED QCowSnapshotExtraData {
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uint64_t vm_state_size_large;
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uint64_t disk_size;
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} QCowSnapshotExtraData;
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void qcow2_free_snapshots(BlockDriverState *bs)
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{
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BDRVQcowState *s = bs->opaque;
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@ -357,6 +332,10 @@ int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
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uint64_t *l1_table = NULL;
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int64_t l1_table_offset;
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if (s->nb_snapshots >= QCOW_MAX_SNAPSHOTS) {
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return -EFBIG;
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}
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memset(sn, 0, sizeof(*sn));
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/* 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,
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goto fail;
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}
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/* Snapshot table offset/length */
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if (header.nb_snapshots > QCOW_MAX_SNAPSHOTS) {
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error_setg(errp, "Too many snapshots");
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ret = -EINVAL;
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goto fail;
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}
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ret = validate_table_offset(bs, header.snapshots_offset,
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header.nb_snapshots,
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sizeof(QCowSnapshotHeader));
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if (ret < 0) {
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error_setg(errp, "Invalid snapshot table offset");
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goto fail;
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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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@ -38,6 +38,7 @@
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#define QCOW_CRYPT_AES 1
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#define QCOW_MAX_CRYPT_CLUSTERS 32
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#define QCOW_MAX_SNAPSHOTS 65536
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/* indicate that the refcount of the referenced cluster is exactly one. */
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#define QCOW_OFLAG_COPIED (1ULL << 63)
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@ -97,6 +98,32 @@ typedef struct QCowHeader {
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uint32_t header_length;
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} QEMU_PACKED QCowHeader;
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typedef struct QEMU_PACKED QCowSnapshotHeader {
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/* header is 8 byte aligned */
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uint64_t l1_table_offset;
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uint32_t l1_size;
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uint16_t id_str_size;
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uint16_t name_size;
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uint32_t date_sec;
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uint32_t date_nsec;
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uint64_t vm_clock_nsec;
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uint32_t vm_state_size;
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uint32_t extra_data_size; /* for extension */
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/* extra data follows */
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/* id_str follows */
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/* name follows */
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} QCowSnapshotHeader;
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typedef struct QEMU_PACKED QCowSnapshotExtraData {
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uint64_t vm_state_size_large;
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uint64_t disk_size;
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} QCowSnapshotExtraData;
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typedef struct QCowSnapshot {
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uint64_t l1_table_offset;
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uint32_t l1_size;
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@ -202,7 +229,7 @@ typedef struct BDRVQcowState {
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AES_KEY aes_decrypt_key;
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uint64_t snapshots_offset;
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int snapshots_size;
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int nb_snapshots;
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unsigned int nb_snapshots;
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QCowSnapshot *snapshots;
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int flags;
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@ -47,6 +47,8 @@ header_size=104
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offset_backing_file_offset=8
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offset_refcount_table_offset=48
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offset_refcount_table_clusters=56
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offset_nb_snapshots=60
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offset_snapshots_offset=64
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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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@ -90,6 +92,31 @@ poke_file "$TEST_IMG" "$offset_refcount_table_offset" "\xff\xff\xff\xff\xff\xff\
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poke_file "$TEST_IMG" "$offset_refcount_table_clusters" "\x00\x00\x00\x7f"
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{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
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echo
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echo "== Invalid snapshot table =="
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_make_test_img 64M
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poke_file "$TEST_IMG" "$offset_nb_snapshots" "\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_nb_snapshots" "\x7f\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" "$offset_snapshots_offset" "\xff\xff\xff\xff\xff\xff\x00\x00"
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poke_file "$TEST_IMG" "$offset_nb_snapshots" "\x00\x00\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" "$offset_snapshots_offset" "\x12\x34\x56\x78\x90\xab\xcd\xef"
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poke_file "$TEST_IMG" "$offset_nb_snapshots" "\x00\x00\x00\x00"
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{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
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echo
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echo "== Hitting snapshot table size limit =="
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_make_test_img 64M
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# Put the refcount table in a more or less safe place (16 MB)
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poke_file "$TEST_IMG" "$offset_snapshots_offset" "\x00\x00\x00\x00\x01\x00\x00\x00"
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poke_file "$TEST_IMG" "$offset_nb_snapshots" "\x00\x01\x00\x00"
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{ $QEMU_IMG snapshot -c test $TEST_IMG; } 2>&1 | _filter_testdir
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{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
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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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@ -30,4 +30,21 @@ no file open, try 'help open'
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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: Invalid reference count table offset
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no file open, try 'help open'
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== Invalid snapshot table ==
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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: Too many snapshots
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no file open, try 'help open'
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qemu-io: can't open device TEST_DIR/t.qcow2: Too many snapshots
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no file open, try 'help open'
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qemu-io: can't open device TEST_DIR/t.qcow2: Invalid snapshot table 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: Invalid snapshot table offset
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no file open, try 'help open'
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== Hitting snapshot table size limit ==
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Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
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qemu-img: Could not create snapshot 'test': -27 (File too large)
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read 512/512 bytes at offset 0
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512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
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*** done
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