go-selinux: retry on EINTR

Wrap some syscalls (lgetattr, lsetattr, fstatfs, statfs)
to retry on EINTR.

Related:
 - containers/storage#757
 - https://go-review.googlesource.com/c/go/+/249178
 - golang/go#38033

Signed-off-by: Kir Kolyshkin <[email protected]>

Author: kolyshkin

go-selinux/selinux_linux.go

@@ -111,7 +111,7 @@ func verifySELinuxfsMount(mnt string) bool {
 		if err == nil {
 			break
 		}
-		if err == unix.EAGAIN {
+		if err == unix.EAGAIN || err == unix.EINTR {
 			continue
 		}
 		return false
@@ -250,8 +250,17 @@ func getSELinuxPolicyRoot() string {
 }
 
 func isProcHandle(fh *os.File) error {
-	var buf unix.Statfs_t
-	err := unix.Fstatfs(int(fh.Fd()), &buf)
+	var (
+		buf unix.Statfs_t
+		err error
+	)
+
+	for {
+		err = unix.Fstatfs(int(fh.Fd()), &buf)
+		if err != unix.EINTR {
+			break
+		}
+	}
 	if err != nil {
 		return errors.Wrapf(err, "statfs(%q) failed", fh.Name())
 	}
@@ -307,9 +316,17 @@ func setFileLabel(fpath string, label string) error {
 	if fpath == "" {
 		return ErrEmptyPath
 	}
-	if err := unix.Lsetxattr(fpath, xattrNameSelinux, []byte(label), 0); err != nil {
+	var err error
+	for {
+		err = unix.Lsetxattr(fpath, xattrNameSelinux, []byte(label), 0)
+		if err != unix.EINTR {
+			break
+		}
+	}
+	if err != nil {
 		return errors.Wrapf(err, "failed to set file label on %s", fpath)
 	}
+
 	return nil
 }
 

go-selinux/xattrs.go

@@ -6,25 +6,35 @@ import (
 	"golang.org/x/sys/unix"
 )
 
-// Returns a []byte slice if the xattr is set and nil otherwise
-// Requires path and its attribute as arguments
-func lgetxattr(path string, attr string) ([]byte, error) {
+// lgetxattr returns a []byte slice containing the value of
+// an extended attribute attr set for path.
+func lgetxattr(path, attr string) ([]byte, error) {
 	// Start with a 128 length byte array
 	dest := make([]byte, 128)
-	sz, errno := unix.Lgetxattr(path, attr, dest)
+	sz, errno := doLgetxattr(path, attr, dest)
 	for errno == unix.ERANGE {
 		// Buffer too small, use zero-sized buffer to get the actual size
-		sz, errno = unix.Lgetxattr(path, attr, []byte{})
+		sz, errno = doLgetxattr(path, attr, []byte{})
 		if errno != nil {
 			return nil, errno
 		}
 
 		dest = make([]byte, sz)
-		sz, errno = unix.Lgetxattr(path, attr, dest)
+		sz, errno = doLgetxattr(path, attr, dest)
 	}
 	if errno != nil {
 		return nil, errno
 	}
 
 	return dest[:sz], nil
 }
+
+// doLgetxattr is a wrapper that retries on EINTR
+func doLgetxattr(path, attr string, dest []byte) (int, error) {
+	for {
+		sz, err := unix.Lgetxattr(path, attr, dest)
+		if err != unix.EINTR {
+			return sz, err
+		}
+	}
+}