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AkihiroSudaAkihiroSuda
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btrfs: Allow unprivileged user to delete subvolumes (kernel >= 4.18)
Fix issue 41762 Cherry-pick "drivers: btrfs: Allow unprivileged user to delete subvolumes" from containers/storage containers/storage@831e32b > 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>
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‎daemon/graphdriver/btrfs/btrfs.go‎

Lines changed: 8 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -633,7 +633,14 @@ func (d *Driver) Remove(id string) error {
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d.updateQuotaStatus()
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if err := subvolDelete(d.subvolumesDir(), id, d.quotaEnabled); err != nil {
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return err
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if d.quotaEnabled {
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return err
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}
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// If quota is not enabled, fallback to rmdir syscall to delete subvolumes.
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// This would allow unprivileged user to delete their owned subvolumes
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// in kernel >= 4.18 without user_subvol_rm_allowed mount option.
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//
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// From https://github.com/containers/storage/pull/508/commits/831e32b6bdcb530acc4c1cb9059d3c6dba14208c
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}
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if err := system.EnsureRemoveAll(dir); err != nil {
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return err

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