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btrfs: Allow unprivileged user to delete subvolumes (kernel >= 4.18)

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Fix issue 41762

Cherry-pick "drivers: btrfs: Allow unprivileged user to delete subvolumes" from containers/storage
831e32b6bd

> In btrfs, subvolume can be deleted by IOC_SNAP_DESTROY ioctl but there
> is one catch: unprivileged IOC_SNAP_DESTROY call is restricted by default.
>
> This is because IOC_SNAP_DESTROY only performs permission checks on
> the top directory(subvolume) and unprivileged user might delete dirs/files
> which cannot be deleted otherwise. This restriction can be relaxed if
> user_subvol_rm_allowed mount option is used.
>
> Although the above ioctl had been the only way to delete a subvolume,
> btrfs now allows deletion of subvolume just like regular directory
> (i.e. rmdir sycall) since kernel 4.18.
>
> So if we fail to cleanup subvolume in subvolDelete(), just fallback to
> system.EnsureRmoveall() to try to cleanup subvolumes again.
> (Note: quota needs privilege, so if quota is enabled we do not fallback)
>
> This fix will allow non-privileged container works with btrfs backend.

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>
This commit is contained in:
Akihiro Suda 2021-03-25 18:56:23 +09:00
parent db2759dbf7
commit 62b5194f62
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GPG key ID: 49524C6F9F638F1A
1 changed files with 8 additions and 1 deletions
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7
daemon/graphdriver/btrfs/btrfs.go
View file

@ -633,8 +633,15 @@ func (d *Driver) Remove(id string) error {
d.updateQuotaStatus() d.updateQuotaStatus()
if err := subvolDelete(d.subvolumesDir(), id, d.quotaEnabled); err != nil { if err := subvolDelete(d.subvolumesDir(), id, d.quotaEnabled); err != nil {
if d.quotaEnabled {
return err return err
} }
// If quota is not enabled, fallback to rmdir syscall to delete subvolumes.
// This would allow unprivileged user to delete their owned subvolumes
// in kernel >= 4.18 without user_subvol_rm_allowed mount option.
//
// From https://github.com/containers/storage/pull/508/commits/831e32b6bdcb530acc4c1cb9059d3c6dba14208c
}
if err := system.EnsureRemoveAll(dir); err != nil { if err := system.EnsureRemoveAll(dir); err != nil {
return err return err
} }