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Use lchown when remapping rootfs

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Use lchown when remapping the container's rootfs as to ensure that the
symlink has the correct permissions but the underlying file that it
points to is not modified.

Remapping on the host can cause host files to change outside of the
rootfs if symlinks are dereferenced.

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>
This commit is contained in:
Michael Crosby 2017-08-09 11:13:44 -04:00
parent ef344c14ba
commit 1f6b10b699
1 changed files with 4 additions and 13 deletions
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17
spec_unix.go
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@ -6,12 +6,10 @@ import (
"io/ioutil"
"os"
"path/filepath"
"strings"
"syscall"
"golang.org/x/sys/unix"
"github.com/containerd/containerd/fs"
"github.com/containerd/containerd/mount"
specs "github.com/opencontainers/runtime-spec/specs-go"
)
@ -177,17 +175,10 @@ func incrementFS(root string, uidInc, gidInc uint32) filepath.WalkFunc {
return nil
}
var (
stat = info.Sys().(*syscall.Stat_t)
u, g = int(stat.Uid + uidInc), int(stat.Gid + gidInc)
symlink = info.Mode()&os.ModeSymlink != 0
stat = info.Sys().(*syscall.Stat_t)
u, g = int(stat.Uid + uidInc), int(stat.Gid + gidInc)
)
// make sure we resolve links inside the root for symlinks
if path, err = fs.RootPath(root, strings.TrimPrefix(path, root)); err != nil {
return err
}
if err := os.Chown(path, u, g); err != nil && !symlink {
return err
}
return nil
// be sure the lchown the path as to not de-reference the symlink to a host file
return os.Lchown(path, u, g)
}
}