[Freedombox-discuss] Bug#988146: parted: Inconsistent behavior creating partitions with 'Xmib' and 'X%' (off-by-1 error?)

[Diederik de Haas]

Package: parted
Version: 3.4-1
Severity: important
X-Debbugs-Cc: freedombox-discuss at alioth-lists.debian.net

I first noticed this when trying to make an improvement to
freedom-maker, hence FB-discuss in CC, while this issue didn't present
itself with the Raspberry Pi image specs project.
The former uses 'mib', while the latter uses '%'.

To demonstrate it, I created a script to prove the issue:
==================================================
#!/bin/sh
BUILD_DIR="temp"
IMAGE_NAME="parted-test.img"
IMAGE_PATH="$BUILD_DIR/$IMAGE_NAME"
IMAGE_SIZE="100M"

echo "BUILD_DIR: $BUILD_DIR"
echo "IMAGE_NAME: $IMAGE_NAME"
echo "IMAGE_PATH: $IMAGE_PATH"
echo "IMAGE_SIZE: $IMAGE_SIZE"

if [ ! -d "$BUILD_DIR" ] ; then
    echo "directory $BUILD_DIR doesn't exist; create it"
    mkdir $BUILD_DIR
fi

echo "Creating image at '$IMAGE_PATH' of size '$IMAGE_SIZE'"
qemu-img create -f raw "$IMAGE_PATH" "$IMAGE_SIZE"
echo "Image file created"

echo -n "Creating partition table ... "
/sbin/parted -s $IMAGE_PATH mklabel msdos
echo "Done"

echo -n "Creating 1st partition ('4mib' '20%') ... "
/sbin/parted -s $IMAGE_PATH mkpart primary fat32 '4mib' '20%'
echo "Done"

echo -n "Creating 2nd partition ('20%' '40%' ... "
/sbin/parted -s $IMAGE_PATH mkpart primary ext4 '20%' '40%'
echo "Done"

echo -n "Creating 3rd partition ('40mib' '60mib') ... "
/sbin/parted -s $IMAGE_PATH mkpart primary ext4 '40mib' '60mib'
echo "Done"

echo ""
echo "Showing partition layout"
/sbin/fdisk -l $IMAGE_PATH

echo ""

echo -n "Creating 4th partition ('60mib' '100%' ... "
/sbin/parted -s $IMAGE_PATH mkpart primary ext4 '60mib' '100%'
echo "Done"

==================================================

And when I run that, I get this output:
==================================================
diederik at bagend:~/tmp/parted$ ./parted-bug-test.sh
BUILD_DIR: temp
IMAGE_NAME: parted-test.img
IMAGE_PATH: temp/parted-test.img
IMAGE_SIZE: 100M
directory temp doesn't exist; create it
Creating image at 'temp/parted-test.img' of size '100M'
Formatting 'temp/parted-test.img', fmt=raw size=104857600
Image file created
Creating partition table ... Done
Creating 1st partition ('4mib' '20%') ... Done
Creating 2nd partition ('20%' '40%' ... Done
Creating 3rd partition ('40mib' '60mib') ... Done

Showing partition layout
Disk temp/parted-test.img: 100 MiB, 104857600 bytes, 204800 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x98f2bc17

Device                Boot Start    End Sectors Size Id Type
temp/parted-test.img1       8192  40959   32768  16M  c W95 FAT32 (LBA)
temp/parted-test.img2      40960  81919   40960  20M 83 Linux
temp/parted-test.img3      81920 122880   40961  20M 83 Linux

Creating 4th partition ('60mib' '100%' ... Error: You requested a partition from 62.9MB to 105MB (sectors 122880..204799).
The closest location we can manage is 62.9MB to 105MB (sectors 122881..204799).
Done
==================================================

As the image size is (deliberately) 100M, one can swap the 'mib' and '%'
values. While it should produce the same output, it does not.

I (strongly) believe that with 'mib' the partition is created 1 sector
too large, hence the off-by-one in the subject.
Consequently, when the 'end' parameter is defined in 'mib' and then try
to create a new partition that starts at the previous end value, the
partition creation fails.


It looks like bug #902224 is related to it and possible also #835172.


Cheers,
  Diederik

-- System Information:
Debian Release: 11.0
  APT prefers unstable-debug
  APT policy: (500, 'unstable-debug'), (500, 'testing-debug'), (500, 'unstable'), (500, 'testing'), (101, 'experimental')
Architecture: amd64 (x86_64)

Kernel: Linux 5.10.0-6-amd64 (SMP w/16 CPU threads)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=en_US
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages parted depends on:
ii  libc6         2.31-12
ii  libparted2    3.4-1
ii  libreadline8  8.1-1
ii  libtinfo6     6.2+20201114-2

parted recommends no packages.

Versions of packages parted suggests:
ii  parted-doc  3.4-1

-- no debconf information