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Merged
merged 5 commits into from
Aug 3, 2023
Merged

contrib/fs-idmap: Minor cleanups #3954

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99340bb
contrib/fs-idmap: Reap childs
rata Aug 1, 2023
821d001
contrib/fs-idmap: Remove not needed flags
rata Aug 1, 2023
882e5fe
contrib/fs-idmap: Check exactly 2 args are received
rata Aug 1, 2023
855c5a0
contrib/fs-idmap: Don't hardcode sleep path
rata Aug 1, 2023
0688288
contrib/fs-idmap: Move logic to a new function
rata Aug 1, 2023
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35 changes: 23 additions & 12 deletions contrib/cmd/fs-idmap/fs-idmap.go
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,6 @@ package main

import (
"fmt"
"log"
"os"
"os/exec"
"syscall"
Expand All @@ -11,40 +10,52 @@ import (
)

func main() {
if len(os.Args) < 2 {
log.Fatalf("usage: %s path_to_mount_set_attr", os.Args[0])
if len(os.Args) != 2 {
fmt.Fprintln(os.Stderr, "usage:", os.Args[0], "path_to_mount_set_attr")
os.Exit(1)
}

src := os.Args[1]
treeFD, err := unix.OpenTree(-1, src, uint(unix.OPEN_TREE_CLONE|unix.OPEN_TREE_CLOEXEC|unix.AT_EMPTY_PATH|unix.AT_RECURSIVE))
if err := supportsIDMap(src); err != nil {
fmt.Fprintln(os.Stderr, "fatal error:", err)
os.Exit(1)
}
}

func supportsIDMap(src string) error {
treeFD, err := unix.OpenTree(unix.AT_FDCWD, src, uint(unix.OPEN_TREE_CLONE|unix.OPEN_TREE_CLOEXEC|unix.AT_EMPTY_PATH))
if err != nil {
log.Fatalf("error calling open_tree %q: %v", src, err)
return fmt.Errorf("error calling open_tree %q: %w", src, err)
}
defer unix.Close(treeFD)

cmd := exec.Command("/usr/bin/sleep", "5")
cmd := exec.Command("sleep", "5")
cmd.SysProcAttr = &syscall.SysProcAttr{
Cloneflags: syscall.CLONE_NEWUSER,
UidMappings: []syscall.SysProcIDMap{{ContainerID: 0, HostID: 65536, Size: 65536}},
GidMappings: []syscall.SysProcIDMap{{ContainerID: 0, HostID: 65536, Size: 65536}},
}
if err := cmd.Start(); err != nil {
log.Fatalf("failed to run the helper binary: %v", err)
return fmt.Errorf("failed to run the helper binary: %w", err)
}
defer func() {
_ = cmd.Process.Kill()
_ = cmd.Wait()
}()

path := fmt.Sprintf("/proc/%d/ns/user", cmd.Process.Pid)
var userNsFile *os.File
if userNsFile, err = os.Open(path); err != nil {
log.Fatalf("unable to get user ns file descriptor: %v", err)
return
return fmt.Errorf("unable to get user ns file descriptor: %w", err)
}
defer userNsFile.Close()

attr := unix.MountAttr{
Attr_set: unix.MOUNT_ATTR_IDMAP,
Userns_fd: uint64(userNsFile.Fd()),
}
if err := unix.MountSetattr(treeFD, "", unix.AT_EMPTY_PATH|unix.AT_RECURSIVE, &attr); err != nil {
log.Fatalf("error calling mount_setattr: %v", err)
if err := unix.MountSetattr(treeFD, "", unix.AT_EMPTY_PATH, &attr); err != nil {
return fmt.Errorf("error calling mount_setattr: %w", err)
}

return nil
}