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To: Wolfgang Bumiller <w.bumiller@proxmox.com>
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<tto4hi2gxxlta3yumimb3gtjc2lyptrkhu3hf6cyfhj33supwr@twn4jty73ixv>
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From: Filip Schauer <f.schauer@proxmox.com>
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Subject: Re: [pbs-devel] [PATCH backup] fix #5946: disks: wipe: ensure GPT
header backup is wiped
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Superseded by:
https://lore.proxmox.com/pbs-devel/20250211162639.141541-1-f.schauer@proxmox.com/
On 06/02/2025 16:01, Wolfgang Bumiller wrote:
> On Wed, Dec 04, 2024 at 11:33:31AM +0100, Filip Schauer wrote:
>> When wiping a block device with a GUID partition table, the header
>> backup might get left behind at the end of the disk. This commit also
>> wipes the last 4096 bytes of the disk, making sure that a GPT header
>> backup is erased, even from disks with 4k sector sizes.
>>
>> Signed-off-by: Filip Schauer <f.schauer@proxmox.com>
>> ---
>> src/tools/disks/mod.rs | 47 +++++++++++++++++++++++++-----------------
>> 1 file changed, 28 insertions(+), 19 deletions(-)
>>
>> diff --git a/src/tools/disks/mod.rs b/src/tools/disks/mod.rs
>> index 61aceccd..26e14603 100644
>> --- a/src/tools/disks/mod.rs
>> +++ b/src/tools/disks/mod.rs
>> @@ -1176,29 +1176,38 @@ pub fn wipe_blockdev(disk: &Disk) -> Result<(), Error> {
>> let wipefs_output = proxmox_sys::command::run_command(wipefs_command, None)?;
>> info!("wipefs output: {wipefs_output}");
>>
>> - let size = disk.size().map(|size| size / 1024 / 1024)?;
>> - let count = size.min(200);
>> -
>> - let mut dd_command = std::process::Command::new("dd");
>> - let mut of_path = OsString::from("of=");
>> - of_path.push(disk_path);
>> - let mut count_str = OsString::from("count=");
>> - count_str.push(count.to_string());
>> - let args = [
>> - "if=/dev/zero".into(),
>> - of_path,
>> - "bs=1M".into(),
>> - "conv=fdatasync".into(),
>> - count_str,
>> - ];
>> - dd_command.args(args);
>> -
>> - let dd_output = proxmox_sys::command::run_command(dd_command, None)?;
>> - info!("dd output: {dd_output}");
>> + let dd_zero = |seek: Option<&str>, bs: &str, count: &str| -> Result<(), Error> {
>> + let mut dd_command = std::process::Command::new("dd");
>> + let mut of_path = OsString::from("of=");
>> + of_path.push(disk_path);
>> + dd_command
>> + .arg("if=/dev/zero")
>> + .arg(of_path)
>> + .arg(format!("bs={bs}"))
>> + .arg("conv=fdatasync")
>> + .arg(format!("count={count}"));
>> +
>> + if let Some(seek) = seek {
>> + dd_command.arg(format!("seek={seek}"));
>> + }
>> +
>> + let dd_output = proxmox_sys::command::run_command(dd_command, None)?;
>> + info!("dd output: {dd_output}");
>> +
>> + Ok(())
>> + };
>> +
>> + let size = disk.size()?;
>> + let count = (size / 1024 / 1024).min(200).to_string();
>> + dd_zero(None, "1M", &count)?;
>>
>> if is_partition {
>> // set the partition type to 0x83 'Linux filesystem'
>> change_parttype(disk, "8300")?;
>> + } else {
>> + // Wipe the end of the disk to remove a potential GPT header backup
>> + let seek = (size / 512 - 8).to_string();
>> + dd_zero(Some(&seek), "512", "8")?;
>> }
>>
>> Ok(())
>> --
>> 2.39.5
> I don't know why we call out to dd for simple writes.
> I'd suggest just using `write_all_at` like so:
>
> ---8<---
> diff --git a/src/tools/disks/mod.rs b/src/tools/disks/mod.rs
> index 571446db..e22691b7 100644
> --- a/src/tools/disks/mod.rs
> +++ b/src/tools/disks/mod.rs
> @@ -4,11 +4,11 @@ use std::collections::{HashMap, HashSet};
> use std::ffi::{OsStr, OsString};
> use std::io;
> use std::os::unix::ffi::{OsStrExt, OsStringExt};
> -use std::os::unix::fs::MetadataExt;
> +use std::os::unix::fs::{FileExt, MetadataExt, OpenOptionsExt};
> use std::path::{Path, PathBuf};
> use std::sync::{Arc, LazyLock};
>
> -use anyhow::{bail, format_err, Error};
> +use anyhow::{bail, format_err, Context as _, Error};
> use libc::dev_t;
> use once_cell::sync::OnceCell;
>
> @@ -1176,25 +1176,7 @@ pub fn wipe_blockdev(disk: &Disk) -> Result<(), Error> {
> let wipefs_output = proxmox_sys::command::run_command(wipefs_command, None)?;
> info!("wipefs output: {wipefs_output}");
>
> - let size = disk.size().map(|size| size / 1024 / 1024)?;
> - let count = size.min(200);
> -
> - let mut dd_command = std::process::Command::new("dd");
> - let mut of_path = OsString::from("of=");
> - of_path.push(disk_path);
> - let mut count_str = OsString::from("count=");
> - count_str.push(count.to_string());
> - let args = [
> - "if=/dev/zero".into(),
> - of_path,
> - "bs=1M".into(),
> - "conv=fdatasync".into(),
> - count_str,
> - ];
> - dd_command.args(args);
> -
> - let dd_output = proxmox_sys::command::run_command(dd_command, None)?;
> - info!("dd output: {dd_output}");
> + zero_start_and_end(disk)?;
>
> if is_partition {
> // set the partition type to 0x83 'Linux filesystem'
> @@ -1204,6 +1186,29 @@ pub fn wipe_blockdev(disk: &Disk) -> Result<(), Error> {
> Ok(())
> }
>
> +pub fn zero_start_and_end(disk: &Disk) -> Result<(), Error> {
> + let disk_path = match disk.device_path() {
> + Some(path) => path,
> + None => bail!("disk {:?} has no node in /dev", disk.syspath()),
> + };
> +
> + let disk_size = disk.size()?;
> + let file = std::fs::OpenOptions::new()
> + .write(true)
> + .custom_flags(libc::O_CLOEXEC | libc::O_DSYNC)
> + .open(disk_path)
> + .with_context(|| "failed to open device {disk_path:?} for writing")?;
> + let write_size = disk_size.min(1024 * 1024);
> + let zeroes = proxmox_io::boxed::zeroed(write_size as usize);
> + file.write_all_at(&zeroes, 0)
> + .with_context(|| "failed to wipe start of device {disk_path:?}")?;
> + if disk_size > 4096 {
> + file.write_all_at(&zeroes[0..4096], disk_size - 4096)
> + .with_context(|| "failed to wipe end of device {disk_path:?}")?;
> + }
> + Ok(())
> +}
> +
> pub fn change_parttype(part_disk: &Disk, part_type: &str) -> Result<(), Error> {
> let part_path = match part_disk.device_path() {
> Some(path) => path,
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