From 624143355cb6e4149ec27b9b00088aeb958da31d Mon Sep 17 00:00:00 2001 From: Max Reitz Date: Fri, 11 Oct 2019 17:28:09 +0200 Subject: [PATCH] qcow2: Keep track of the snapshot table length When repairing the snapshot table, we truncate entries that have too much extra data. This frees up space that we do not have to count towards the snapshot table size. Signed-off-by: Max Reitz Reviewed-by: Eric Blake Message-id: 20191011152814.14791-12-mreitz@redhat.com Signed-off-by: Max Reitz --- block/qcow2-snapshot.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c index 53dc1635ec..582eb3386a 100644 --- a/block/qcow2-snapshot.c +++ b/block/qcow2-snapshot.c @@ -68,6 +68,7 @@ static int qcow2_do_read_snapshots(BlockDriverState *bs, bool repair, QCowSnapshot *sn; int i, id_str_size, name_size; int64_t offset; + uint64_t table_length = 0; int ret; if (!s->nb_snapshots) { @@ -82,6 +83,8 @@ static int qcow2_do_read_snapshots(BlockDriverState *bs, bool repair, for(i = 0; i < s->nb_snapshots; i++) { bool truncate_unknown_extra_data = false; + table_length = ROUND_UP(table_length, 8); + /* Read statically sized part of the snapshot header */ offset = ROUND_UP(offset, 8); ret = bdrv_pread(bs->file, offset, &h, sizeof(h)); @@ -184,7 +187,16 @@ static int qcow2_do_read_snapshots(BlockDriverState *bs, bool repair, offset += name_size; sn->name[name_size] = '\0'; - if (offset - s->snapshots_offset > QCOW_MAX_SNAPSHOTS_SIZE) { + /* Note that the extra data may have been truncated */ + table_length += sizeof(h) + sn->extra_data_size + id_str_size + + name_size; + if (!repair) { + assert(table_length == offset - s->snapshots_offset); + } + + if (table_length > QCOW_MAX_SNAPSHOTS_SIZE || + offset - s->snapshots_offset > INT_MAX) + { ret = -EFBIG; error_setg(errp, "Snapshot table is too big"); goto fail;