cdi: resolve symlinks

Fix using /etc/cdi entries in rootless mode:

> level=warning msg="Refreshing the CDI registry generated errors"
> error="failed to monitor for changes: no such file or directory\nfailed to monitor for changes: no such file or directory"

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

daemon/cdi.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"fmt"
 	"os"
+	"path/filepath"
 
 	"github.com/containerd/log"
 	"github.com/moby/moby/api/types/system"
@@ -22,6 +23,14 @@ type cdiHandler struct {
 // The driver injects CDI devices into an incoming OCI spec and is called for DeviceRequests associated with CDI devices.
 // If the list of CDI spec directories is empty, the driver is not registered.
 func RegisterCDIDriver(cdiSpecDirs ...string) *cdi.Cache {
+	for i, dir := range cdiSpecDirs {
+		if _, err := os.Stat(dir); !errors.Is(err, os.ErrNotExist) {
+			cdiSpecDirs[i], err = filepath.EvalSymlinks(dir)
+			if err != nil {
+				log.L.WithField("dir", dir).WithError(err).Warn("Failed to evaluate symlinks for CDI spec directory")
+			}
+		}
+	}
 	driver, cache := newCDIDeviceDriver(cdiSpecDirs...)
 	registerDeviceDriver("cdi", driver)
 	return cache