From 1037269fec43e8055c530c13d4fd58819e86b233 Mon Sep 17 00:00:00 2001 From: Tobias Stoeckmann Date: Sat, 27 Aug 2016 19:28:48 +0200 Subject: libfdisk: Distinguish between first LBA sector and partition An insufficient check leads to an invalid free space output, as seen here: $ dd if=/dev/zero of=cfdisk.iso bs=1M count=1 $ losetup -f cfdisk.iso $ echo w | fdisk /dev/loop0 $ echo '1,1' | sfdisk /dev/loop0 --append $ echo '3,' | sfdisk /dev/loop0 --append $ sfdisk --list-free /dev/loop0 Start End Sectors Size 1 2 2 1K $ _ In this case, libfdisk fails to notice that it tries to calculate space between two partitions, not between start of disk and first partition. Currently, the code tries to achieve that by checking the address of the last "partition", which is the first_lba block. Now if the first partition is merely 1 block in size, the "last" address is still equal to the first_lba block, which renders the check in libfdisk for the next partition invalid. I chose to use "nparts == 0" for this check, because the partitions are properly sorted before iterating over them. Signed-off-by: Tobias Stoeckmann --- libfdisk/src/table.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'libfdisk') diff --git a/libfdisk/src/table.c b/libfdisk/src/table.c index bf30d1b19..f9751686b 100644 --- a/libfdisk/src/table.c +++ b/libfdisk/src/table.c @@ -617,9 +617,9 @@ int fdisk_get_freespaces(struct fdisk_context *cxt, struct fdisk_table **tb) * aligned, the exception is space before the first partition where * we assume that cxt->first_lba is aligned. */ if (last + grain < pa->start - || (last < pa->start && last == cxt->first_lba)) { + || (last < pa->start && nparts == 0)) { rc = table_add_freespace(cxt, *tb, - last + (last > cxt->first_lba ? 1 : 0), + last + (nparts == 0 ? 0 : 1), pa->start - 1, NULL); } /* add gaps between logical partitions */ -- cgit v1.2.3-55-g7522