From 24bae02b197d152c2b3e4e0ba95f7942a63bad32 Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Fri, 21 Jul 2017 13:32:43 -0500 Subject: [PATCH] qcow2: Fix sector calculation in qcow2_measure() We used MAX() instead of the intended MIN() when computing how many sectors to view in the current loop iteration of qcow2_measure(), and passed in a value of INT_MAX sectors instead of our more usual limit of BDRV_REQUEST_MAX_SECTORS (the latter avoids 32-bit overflow on conversion to bytes). For small files, the bug is harmless: bdrv_get_block_status_above() clamps its *pnum answer to the BDS size, regardless of any insanely larger input request. However, for any file at least 2T in size, we can very easily end up going into an infinite loop (the maximum of 0x100000000 sectors and INT_MAX is a 64-bit quantity, which becomes 0 when assigned to int; once nb_sectors is 0, we never make progress). Signed-off-by: Eric Blake Reviewed-by: Stefan Hajnoczi Signed-off-by: Kevin Wolf --- block/qcow2.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/block/qcow2.c b/block/qcow2.c index d5790af1e0..90efa4477b 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -3669,8 +3669,8 @@ static BlockMeasureInfo *qcow2_measure(QemuOpts *opts, BlockDriverState *in_bs, for (sector_num = 0; sector_num < ssize / BDRV_SECTOR_SIZE; sector_num += pnum) { - int nb_sectors = MAX(ssize / BDRV_SECTOR_SIZE - sector_num, - INT_MAX); + int nb_sectors = MIN(ssize / BDRV_SECTOR_SIZE - sector_num, + BDRV_REQUEST_MAX_SECTORS); BlockDriverState *file; int64_t ret;