Set file mode and type to attribute

Makes less error prone to find file type.

Updates #1197

PiperOrigin-RevId: 302974244

pkg/sentry/fsimpl/tmpfs/device_file.go

@@ -15,6 +15,8 @@
 package tmpfs
 
 import (
+	"fmt"
+
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
@@ -33,6 +35,14 @@ func (fs *filesystem) newDeviceFile(creds *auth.Credentials, mode linux.FileMode
 		major: major,
 		minor: minor,
 	}
+	switch kind {
+	case vfs.BlockDevice:
+		mode |= linux.S_IFBLK
+	case vfs.CharDevice:
+		mode |= linux.S_IFCHR
+	default:
+		panic(fmt.Sprintf("invalid DeviceKind: %v", kind))
+	}
 	file.inode.init(file, fs, creds, mode)
 	file.inode.nlink = 1 // from parent directory
 	return &file.inode

pkg/sentry/fsimpl/tmpfs/directory.go

@@ -34,16 +34,11 @@ type directory struct {
 
 func (fs *filesystem) newDirectory(creds *auth.Credentials, mode linux.FileMode) *inode {
 	dir := &directory{}
-	dir.inode.init(dir, fs, creds, mode)
+	dir.inode.init(dir, fs, creds, linux.S_IFDIR|mode)
 	dir.inode.nlink = 2 // from "." and parent directory or ".." for root
 	return &dir.inode
 }
 
-func (i *inode) isDir() bool {
-	_, ok := i.impl.(*directory)
-	return ok
-}
-
 type directoryFD struct {
 	fileDescription
 	vfs.DirectoryFileDescriptionDefaultImpl

pkg/sentry/fsimpl/tmpfs/named_pipe.go

@@ -34,7 +34,7 @@ type namedPipe struct {
 //   * rp.Mount().CheckBeginWrite() has been called successfully.
 func (fs *filesystem) newNamedPipe(creds *auth.Credentials, mode linux.FileMode) *inode {
 	file := &namedPipe{pipe: pipe.NewVFSPipe(pipe.DefaultPipeSize, usermem.PageSize)}
-	file.inode.init(file, fs, creds, mode)
+	file.inode.init(file, fs, creds, linux.S_IFIFO|mode)
 	file.inode.nlink = 1 // Only the parent has a link.
 	return &file.inode
 }

pkg/sentry/fsimpl/tmpfs/regular_file.go

@@ -89,7 +89,7 @@ func (fs *filesystem) newRegularFile(creds *auth.Credentials, mode linux.FileMod
 	file := &regularFile{
 		memFile: fs.memFile,
 	}
-	file.inode.init(file, fs, creds, mode)
+	file.inode.init(file, fs, creds, linux.S_IFREG|mode)
 	file.inode.nlink = 1 // from parent directory
 	return &file.inode
 }

pkg/sentry/fsimpl/tmpfs/symlink.go

@@ -15,6 +15,7 @@
 package tmpfs
 
 import (
+	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 )
 
@@ -27,7 +28,7 @@ func (fs *filesystem) newSymlink(creds *auth.Credentials, target string) *inode
 	link := &symlink{
 		target: target,
 	}
-	link.inode.init(link, fs, creds, 0777)
+	link.inode.init(link, fs, creds, linux.S_IFLNK|0777)
 	link.inode.nlink = 1 // from parent directory
 	return &link.inode
 }

pkg/sentry/fsimpl/tmpfs/tmpfs.go

@@ -144,7 +144,7 @@ type inode struct {
 	// Inode metadata. Writing multiple fields atomically requires holding
 	// mu, othewise atomic operations can be used.
 	mu    sync.Mutex
-	mode  uint32 // excluding file type bits, which are based on impl
+	mode  uint32 // file type and mode
 	nlink uint32 // protected by filesystem.mu instead of inode.mu
 	uid   uint32 // auth.KUID, but stored as raw uint32 for sync/atomic
 	gid   uint32 // auth.KGID, but ...
@@ -168,6 +168,9 @@ type inode struct {
 const maxLinks = math.MaxUint32
 
 func (i *inode) init(impl interface{}, fs *filesystem, creds *auth.Credentials, mode linux.FileMode) {
+	if mode.FileType() == 0 {
+		panic("file type is required in FileMode")
+	}
 	i.clock = fs.clock
 	i.refs = 1
 	i.mode = uint32(mode)
@@ -269,31 +272,21 @@ func (i *inode) statTo(stat *linux.Statx) {
 	// TODO(gvisor.dev/issues/1197): Device number.
 	switch impl := i.impl.(type) {
 	case *regularFile:
-		stat.Mode |= linux.S_IFREG
 		stat.Mask |= linux.STATX_SIZE | linux.STATX_BLOCKS
 		stat.Size = uint64(atomic.LoadUint64(&impl.size))
 		// In tmpfs, this will be FileRangeSet.Span() / 512 (but also cached in
 		// a uint64 accessed using atomic memory operations to avoid taking
 		// locks).
 		stat.Blocks = allocatedBlocksForSize(stat.Size)
-	case *directory:
-		stat.Mode |= linux.S_IFDIR
 	case *symlink:
-		stat.Mode |= linux.S_IFLNK
 		stat.Mask |= linux.STATX_SIZE | linux.STATX_BLOCKS
 		stat.Size = uint64(len(impl.target))
 		stat.Blocks = allocatedBlocksForSize(stat.Size)
-	case *namedPipe:
-		stat.Mode |= linux.S_IFIFO
 	case *deviceFile:
-		switch impl.kind {
-		case vfs.BlockDevice:
-			stat.Mode |= linux.S_IFBLK
-		case vfs.CharDevice:
-			stat.Mode |= linux.S_IFCHR
-		}
 		stat.RdevMajor = impl.major
 		stat.RdevMinor = impl.minor
+	case *directory, *namedPipe:
+		// Nothing to do.
 	default:
 		panic(fmt.Sprintf("unknown inode type: %T", i.impl))
 	}
@@ -316,7 +309,8 @@ func (i *inode) setStat(ctx context.Context, creds *auth.Credentials, stat *linu
 	)
 	mask := stat.Mask
 	if mask&linux.STATX_MODE != 0 {
-		atomic.StoreUint32(&i.mode, uint32(stat.Mode))
+		ft := atomic.LoadUint32(&i.mode) & linux.S_IFMT
+		atomic.StoreUint32(&i.mode, ft|uint32(stat.Mode&^linux.S_IFMT))
 		needsCtimeBump = true
 	}
 	if mask&linux.STATX_UID != 0 {
@@ -439,6 +433,10 @@ func (i *inode) direntType() uint8 {
 	}
 }
 
+func (i *inode) isDir() bool {
+	return linux.FileMode(i.mode).FileType() == linux.S_IFDIR
+}
+
 // fileDescription is embedded by tmpfs implementations of
 // vfs.FileDescriptionImpl.
 type fileDescription struct {