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use std::path::Path;
use anyhow::anyhow;
use anyhow::Context;
use anyhow::Result;
use log::debug;
use log::error;
use log::warn;
use nix::mount::mount;
use nix::mount::MsFlags;
use proc_mounts::MountIter;
const EFIVARS_MOUNT_POINT: &str = "/sys/firmware/efi/efivars";
pub struct EfivarsMountGuard {
original_flags: MsFlags,
}
impl EfivarsMountGuard {
pub fn new() -> Result<Self> {
let original_flags = get_current_mount_flags(EFIVARS_MOUNT_POINT)?;
if original_flags.contains(MsFlags::MS_RDONLY) {
debug!(
"{} mounted read only, remounting read/write",
EFIVARS_MOUNT_POINT
);
mount(
None as Option<&str>,
EFIVARS_MOUNT_POINT,
None as Option<&str>,
original_flags & !MsFlags::MS_RDONLY | MsFlags::MS_REMOUNT,
None as Option<&str>,
)
.context(format!("Failed to remount {} RW", EFIVARS_MOUNT_POINT))?
} else {
debug!(
"{} is mounted read/write, skipping remount",
EFIVARS_MOUNT_POINT
);
}
Ok(EfivarsMountGuard { original_flags })
}
}
impl Drop for EfivarsMountGuard {
fn drop(&mut self) {
// efivarfs being rw is scary. We should unmount it ASAP.
// If efivarfs is set as ro in fstab (the ideal), "remount" along will change it back.
if self.original_flags.contains(MsFlags::MS_RDONLY) {
debug!("remounting {} as read only", EFIVARS_MOUNT_POINT);
let res = mount(
None as Option<&str>,
EFIVARS_MOUNT_POINT,
None as Option<&str>,
self.original_flags | MsFlags::MS_REMOUNT,
None as Option<&str>,
);
if let Err(why) = res {
error!(
"failed to remount {} because {:#}",
EFIVARS_MOUNT_POINT, why
);
}
}
}
}
pub fn get_current_mount_flags(dest: impl AsRef<Path>) -> Result<MsFlags> {
let dest = dest.as_ref();
match MountIter::new()
.context("cannot read /proc/mounts")?
.filter_map(Result::ok)
.find(|m| m.dest == dest)
{
Some(mount_info) => {
debug!("MountInfo for {}: {}", dest.to_string_lossy(), mount_info);
Ok(to_ms_flags(&mount_info.options))
}
None => Err(anyhow!(
"mount {} is not in /proc/mounts",
dest.to_string_lossy()
)),
}
}
fn to_ms_flags(options: &[String]) -> MsFlags {
options
.iter()
.fold(MsFlags::empty(), |acc, option| match option.as_str() {
"ro" => acc | MsFlags::MS_RDONLY,
"rw" => acc, // rw means MS_RDONLY is not set
"noexec" => acc | MsFlags::MS_NOEXEC,
"nosuid" => acc | MsFlags::MS_NOSUID,
"nodev" => acc | MsFlags::MS_NODEV,
"sync" => acc | MsFlags::MS_SYNCHRONOUS,
"dirsync" => acc | MsFlags::MS_DIRSYNC,
"remount" => acc | MsFlags::MS_REMOUNT,
"bind" => acc | MsFlags::MS_BIND,
"rbind" => acc | MsFlags::MS_BIND | MsFlags::MS_REC,
"silent" => acc | MsFlags::MS_SILENT,
"mand" => acc | MsFlags::MS_MANDLOCK,
"noatime" => acc | MsFlags::MS_NOATIME,
"iversion" => acc | MsFlags::MS_I_VERSION,
"nodiratime" => acc | MsFlags::MS_NODIRATIME,
"relatime" => acc | MsFlags::MS_RELATIME,
"strictatime" => acc | MsFlags::MS_STRICTATIME,
"lazytime" => acc | MsFlags::MS_LAZYTIME,
"unbindable" => acc | MsFlags::MS_UNBINDABLE,
"runbindable" => acc | MsFlags::MS_UNBINDABLE | MsFlags::MS_REC,
"private" => acc | MsFlags::MS_PRIVATE,
"rprivate" => acc | MsFlags::MS_PRIVATE | MsFlags::MS_REC,
"slave" => acc | MsFlags::MS_SLAVE,
"rslave" => acc | MsFlags::MS_SLAVE | MsFlags::MS_REC,
"shared" => acc | MsFlags::MS_SHARED,
"rshared" => acc | MsFlags::MS_SHARED | MsFlags::MS_REC,
unknown => {
warn!("unknown mount option: {}", &unknown);
acc
}
})
}
#[cfg(test)]
pub mod tests {
use anyhow::Context;
use anyhow::Result;
use super::*;
#[test]
fn test_get_current_mount_flags_not_mounted() -> Result<()> {
assert!(
get_current_mount_flags("some random stuff").is_err(),
"error expected"
);
Ok(())
}
#[test]
fn test_get_current_mount_flags_for_root() -> Result<()> {
let _options =
get_current_mount_flags("/").context("failed to get current mount options for /")?;
Ok(())
}
#[test]
fn test_get_current_mount_flags_for_proc() -> Result<()> {
let options = get_current_mount_flags("/proc")
.context("failed to get current mount options for /")?;
assert!(
options.contains(MsFlags::MS_NODEV | MsFlags::MS_NOEXEC | MsFlags::MS_NOSUID),
"expected /proc to be mounted with nodev, noexec, nosuid"
);
assert!(
!options.contains(MsFlags::MS_REMOUNT),
"remount is not expected for /proc"
);
Ok(())
}
}