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Merge pull request #7772 from mathis-m/fix/userxattr_on_tmpfs

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fix: check for tmpfs when evaluating if userxattr is needed
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Derek McGowan 2022-12-08 16:02:08 -08:00 committed by GitHub
commit f3368b4a5b
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1 changed files with 26 additions and 0 deletions
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26
snapshots/overlay/overlayutils/check.go
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@ -23,6 +23,7 @@ import (
"fmt" "fmt"
"os" "os"
"path/filepath" "path/filepath"
"syscall"
kernel "github.com/containerd/containerd/contrib/seccomp/kernelversion" kernel "github.com/containerd/containerd/contrib/seccomp/kernelversion"
"github.com/containerd/containerd/log" "github.com/containerd/containerd/log"
@ -31,6 +32,11 @@ import (
"github.com/containerd/continuity/fs" "github.com/containerd/continuity/fs"
) )
const (
// see https://man7.org/linux/man-pages/man2/statfs.2.html
tmpfsMagic = 0x01021994
)
// SupportsMultipleLowerDir checks if the system supports multiple lowerdirs, // SupportsMultipleLowerDir checks if the system supports multiple lowerdirs,
// which is required for the overlay snapshotter. On 4.x kernels, multiple lowerdirs // which is required for the overlay snapshotter. On 4.x kernels, multiple lowerdirs
// are always available (so this check isn't needed), and backported to RHEL and // are always available (so this check isn't needed), and backported to RHEL and
@ -88,6 +94,21 @@ func Supported(root string) error {
return SupportsMultipleLowerDir(root) return SupportsMultipleLowerDir(root)
} }
// IsPathOnTmpfs returns whether the path is on a tmpfs or not.
//
// It uses statfs to check if the fs type is TMPFS_MAGIC (0x01021994)
// see https://man7.org/linux/man-pages/man2/statfs.2.html
func IsPathOnTmpfs(d string) bool {
stat := syscall.Statfs_t{}
err := syscall.Statfs(d, &stat)
if err != nil {
log.L.WithError(err).Warnf("Could not retrieve statfs for %v", d)
return false
}
return stat.Type == tmpfsMagic
}
// NeedsUserXAttr returns whether overlayfs should be mounted with the "userxattr" mount option. // NeedsUserXAttr returns whether overlayfs should be mounted with the "userxattr" mount option.
// //
// The "userxattr" option is needed for mounting overlayfs inside a user namespace with kernel >= 5.11. // The "userxattr" option is needed for mounting overlayfs inside a user namespace with kernel >= 5.11.
@ -114,6 +135,11 @@ func NeedsUserXAttr(d string) (bool, error) {
return false, nil return false, nil
} }
// userxattr not permitted on tmpfs https://man7.org/linux/man-pages/man5/tmpfs.5.html
if IsPathOnTmpfs(d) {
return false, nil
}
// Fast path on kernels >= 5.11 // Fast path on kernels >= 5.11
// //
// Keep in mind that distro vendors might be going to backport the patch to older kernels // Keep in mind that distro vendors might be going to backport the patch to older kernels