06.03.2019 2:43, John Snow wrote:
> If we were to allow resizes, the length check that happens when we load
> bitmap headers from disk when we read or store bitmaps would begin to
> fail:
>
> Imagine the circumstance where we've resized bitmaps in memory, but they still
> have the old values on-disk. The lengths will no longer match bdrv_getlength,
> so we must allow this check to be skipped when flushing bitmaps to disk.
>
> Limit this to when we are about to overwrite the headers: we will verify the
> outgoing headers, but we will skip verifying the known stale headers.
>
> Signed-off-by: John Snow <js...@redhat.com>
> ---
> block/qcow2-bitmap.c | 34 +++++++++++++++++++++-------------
> 1 file changed, 21 insertions(+), 13 deletions(-)
>
> diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c
> index c3b210ede1..d02730004a 100644
> --- a/block/qcow2-bitmap.c
> +++ b/block/qcow2-bitmap.c
> @@ -435,7 +435,8 @@ static inline Qcow2BitmapDirEntry
> *next_dir_entry(Qcow2BitmapDirEntry *entry)
> return (Qcow2BitmapDirEntry *)((uint8_t *)entry +
> dir_entry_size(entry));
> }
>
> -static int check_dir_entry(BlockDriverState *bs, Qcow2BitmapDirEntry *entry)
> +static int check_dir_entry(BlockDriverState *bs, Qcow2BitmapDirEntry *entry,
> + bool allow_resize)
> {
> BDRVQcow2State *s = bs->opaque;
> uint64_t phys_bitmap_bytes;
> @@ -462,8 +463,14 @@ static int check_dir_entry(BlockDriverState *bs,
> Qcow2BitmapDirEntry *entry)
> return len;
> }
>
> - fail = (phys_bitmap_bytes > BME_MAX_PHYS_SIZE) ||
> - (len > ((phys_bitmap_bytes * 8) << entry->granularity_bits));
> + if (phys_bitmap_bytes > BME_MAX_PHYS_SIZE) {
> + return -EINVAL;
> + }
> +
> + if (!allow_resize &&
> + (len > ((phys_bitmap_bytes * 8) << entry->granularity_bits))) {
> + return -EINVAL;
> + }
>
> return fail ? -EINVAL : 0;
> }
> @@ -534,7 +541,8 @@ static uint32_t bitmap_list_count(Qcow2BitmapList
> *bm_list)
> * checks it and convert to bitmap list.
> */
> static Qcow2BitmapList *bitmap_list_load(BlockDriverState *bs, uint64_t
> offset,
> - uint64_t size, Error **errp)
> + uint64_t size, bool allow_resize,
> + Error **errp)
> {
> int ret;
> BDRVQcow2State *s = bs->opaque;
> @@ -593,7 +601,7 @@ static Qcow2BitmapList *bitmap_list_load(BlockDriverState
> *bs, uint64_t offset,
> goto fail;
> }
>
> - ret = check_dir_entry(bs, e);
> + ret = check_dir_entry(bs, e, allow_resize);
> if (ret < 0) {
> error_setg(errp, "Bitmap '%.*s' doesn't satisfy the
> constraints",
> e->name_size, dir_entry_name_field(e));
> @@ -654,7 +662,7 @@ int qcow2_check_bitmaps_refcounts(BlockDriverState *bs,
> BdrvCheckResult *res,
> }
>
> bm_list = bitmap_list_load(bs, s->bitmap_directory_offset,
> - s->bitmap_directory_size, NULL);
> + s->bitmap_directory_size, false, NULL);
> if (bm_list == NULL) {
> res->corruptions++;
> return -EINVAL;
> @@ -755,7 +763,7 @@ static int bitmap_list_store(BlockDriverState *bs,
> Qcow2BitmapList *bm_list,
> e->extra_data_size = 0;
> memcpy(e + 1, bm->name, e->name_size);
>
> - if (check_dir_entry(bs, e) < 0) {
> + if (check_dir_entry(bs, e, false) < 0) {
> ret = -EINVAL;
> goto fail;
> }
> @@ -957,7 +965,7 @@ bool qcow2_load_dirty_bitmaps(BlockDriverState *bs, Error
> **errp)
> }
>
> bm_list = bitmap_list_load(bs, s->bitmap_directory_offset,
> - s->bitmap_directory_size, errp);
> + s->bitmap_directory_size, false, errp);
> if (bm_list == NULL) {
> return false;
> }
> @@ -1066,7 +1074,7 @@ Qcow2BitmapInfoList
> *qcow2_get_bitmap_info_list(BlockDriverState *bs,
> }
>
> bm_list = bitmap_list_load(bs, s->bitmap_directory_offset,
> - s->bitmap_directory_size, errp);
> + s->bitmap_directory_size, false, errp);
> if (bm_list == NULL) {
> return NULL;
> }
> @@ -1111,7 +1119,7 @@ int qcow2_reopen_bitmaps_rw_hint(BlockDriverState *bs,
> bool *header_updated,
> }
>
> bm_list = bitmap_list_load(bs, s->bitmap_directory_offset,
> - s->bitmap_directory_size, errp);
> + s->bitmap_directory_size, false, errp);
> if (bm_list == NULL) {
> return -EINVAL;
> }
> @@ -1359,7 +1367,7 @@ void
> qcow2_remove_persistent_dirty_bitmap(BlockDriverState *bs,
> }
>
> bm_list = bitmap_list_load(bs, s->bitmap_directory_offset,
> - s->bitmap_directory_size, errp);
> + s->bitmap_directory_size, false, errp);
> if (bm_list == NULL) {
> return;
> }
> @@ -1412,7 +1420,7 @@ void
> qcow2_store_persistent_dirty_bitmaps(BlockDriverState *bs, Error **errp)
> bm_list = bitmap_list_new();
> } else {
Worth comment here, that we assume that image may be resized?
> bm_list = bitmap_list_load(bs, s->bitmap_directory_offset,
> - s->bitmap_directory_size, errp);
> + s->bitmap_directory_size, true, errp);
> if (bm_list == NULL) {
> return;
> }
> @@ -1593,7 +1601,7 @@ bool qcow2_can_store_new_dirty_bitmap(BlockDriverState
> *bs,
> }
>
> bm_list = bitmap_list_load(bs, s->bitmap_directory_offset,
> - s->bitmap_directory_size, errp);
> + s->bitmap_directory_size, false, errp);
> if (bm_list == NULL) {
> goto fail;
> }
>
With Eric's suggestion:
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
--
Best regards,
Vladimir
