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package rootless
import (
"errors"
"fmt"
"os"
"sort"
"sync"
"github.com/containers/storage/pkg/lockfile"
"github.com/opencontainers/runc/libcontainer/user"
spec "github.com/opencontainers/runtime-spec/specs-go"
)
// TryJoinPauseProcess attempts to join the namespaces of the pause PID via
// TryJoinFromFilePaths. If joining fails, it attempts to delete the specified
// file.
func TryJoinPauseProcess(pausePidPath string) (bool, int, error) {
if _, err := os.Stat(pausePidPath); err != nil {
if errors.Is(err, os.ErrNotExist) {
return false, -1, nil
}
return false, -1, err
}
became, ret, err := TryJoinFromFilePaths("", false, []string{pausePidPath})
if err == nil {
return became, ret, nil
}
// It could not join the pause process, let's lock the file before trying to delete it.
pidFileLock, err := lockfile.GetLockfile(pausePidPath)
if err != nil {
// The file was deleted by another process.
if os.IsNotExist(err) {
return false, -1, nil
}
return false, -1, fmt.Errorf("error acquiring lock on %s: %w", pausePidPath, err)
}
pidFileLock.Lock()
defer func() {
if pidFileLock.Locked() {
pidFileLock.Unlock()
}
}()
// Now the pause PID file is locked. Try to join once again in case it changed while it was not locked.
became, ret, err = TryJoinFromFilePaths("", false, []string{pausePidPath})
if err != nil {
// It is still failing. We can safely remove it.
os.Remove(pausePidPath)
return false, -1, nil // nolint: nilerr
}
return became, ret, err
}
var (
uidMap []user.IDMap
uidMapError error
uidMapOnce sync.Once
gidMap []user.IDMap
gidMapError error
gidMapOnce sync.Once
)
// GetAvailableUIDMap returns the UID mappings in the
// current user namespace.
func GetAvailableUIDMap() ([]user.IDMap, error) {
uidMapOnce.Do(func() {
var err error
uidMap, err = user.ParseIDMapFile("/proc/self/uid_map")
if err != nil {
uidMapError = err
return
}
})
return uidMap, uidMapError
}
// GetAvailableGIDMap returns the GID mappings in the
// current user namespace.
func GetAvailableGIDMap() ([]user.IDMap, error) {
gidMapOnce.Do(func() {
var err error
gidMap, err = user.ParseIDMapFile("/proc/self/gid_map")
if err != nil {
gidMapError = err
return
}
})
return gidMap, gidMapError
}
// GetAvailableIDMaps returns the UID and GID mappings in the
// current user namespace.
func GetAvailableIDMaps() ([]user.IDMap, []user.IDMap, error) {
u, err := GetAvailableUIDMap()
if err != nil {
return nil, nil, err
}
g, err := GetAvailableGIDMap()
if err != nil {
return nil, nil, err
}
return u, g, nil
}
func countAvailableIDs(mappings []user.IDMap) int64 {
availableUids := int64(0)
for _, r := range mappings {
availableUids += r.Count
}
return availableUids
}
// GetAvailableUids returns how many UIDs are available in the
// current user namespace.
func GetAvailableUids() (int64, error) {
uids, err := GetAvailableUIDMap()
if err != nil {
return -1, err
}
return countAvailableIDs(uids), nil
}
// GetAvailableGids returns how many GIDs are available in the
// current user namespace.
func GetAvailableGids() (int64, error) {
gids, err := GetAvailableGIDMap()
if err != nil {
return -1, err
}
return countAvailableIDs(gids), nil
}
// findIDInMappings find the the mapping that contains the specified ID.
// It assumes availableMappings is sorted by ID.
func findIDInMappings(id int64, availableMappings []user.IDMap) *user.IDMap {
i := sort.Search(len(availableMappings), func(i int) bool {
return availableMappings[i].ID <= id
})
if i < 0 || i >= len(availableMappings) {
return nil
}
r := &availableMappings[i]
if id >= r.ID && id < r.ID+r.Count {
return r
}
return nil
}
// MaybeSplitMappings checks whether the specified OCI mappings are possible
// in the current user namespace or the specified ranges must be split.
func MaybeSplitMappings(mappings []spec.LinuxIDMapping, availableMappings []user.IDMap) []spec.LinuxIDMapping {
var ret []spec.LinuxIDMapping
var overflow spec.LinuxIDMapping
overflow.Size = 0
consumed := 0
sort.Slice(availableMappings, func(i, j int) bool {
return availableMappings[i].ID > availableMappings[j].ID
})
for {
cur := overflow
// if there is no overflow left from the previous request, get the next one
if cur.Size == 0 {
if consumed == len(mappings) {
// all done
return ret
}
cur = mappings[consumed]
consumed++
}
// Find the range where the first specified ID is present
r := findIDInMappings(int64(cur.HostID), availableMappings)
if r == nil {
// The requested range is not available. Just return the original request
// and let other layers deal with it.
return mappings
}
offsetInRange := cur.HostID - uint32(r.ID)
usableIDs := uint32(r.Count) - offsetInRange
// the current range can satisfy the whole request
if usableIDs >= cur.Size {
// reset the overflow
overflow.Size = 0
} else {
// the current range can satisfy the request partially
// so move the rest to overflow
overflow.Size = cur.Size - usableIDs
overflow.ContainerID = cur.ContainerID + usableIDs
overflow.HostID = cur.HostID + usableIDs
// and cap to the usableIDs count
cur.Size = usableIDs
}
ret = append(ret, cur)
}
}
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