Add limit_host_fd_translation Gofer mount option.

PiperOrigin-RevId: 266177409

pkg/sentry/fs/fsutil/inode_cached.go

@@ -66,10 +66,8 @@ type CachingInodeOperations struct {
 	// mfp is used to allocate memory that caches backingFile's contents.
 	mfp pgalloc.MemoryFileProvider
 
-	// forcePageCache indicates the sentry page cache should be used regardless
-	// of whether the platform supports host mapped I/O or not. This must not be
-	// modified after inode creation.
-	forcePageCache bool
+	// opts contains options. opts is immutable.
+	opts CachingInodeOperationsOptions
 
 	attrMu sync.Mutex `state:"nosave"`
 
@@ -116,6 +114,20 @@ type CachingInodeOperations struct {
 	refs frameRefSet
 }
 
+// CachingInodeOperationsOptions configures a CachingInodeOperations.
+//
+// +stateify savable
+type CachingInodeOperationsOptions struct {
+	// If ForcePageCache is true, use the sentry page cache even if a host file
+	// descriptor is available.
+	ForcePageCache bool
+
+	// If LimitHostFDTranslation is true, apply maxFillRange() constraints to
+	// host file descriptor mappings returned by
+	// CachingInodeOperations.Translate().
+	LimitHostFDTranslation bool
+}
+
 // CachedFileObject is a file that may require caching.
 type CachedFileObject interface {
 	// ReadToBlocksAt reads up to dsts.NumBytes() bytes from the file to dsts,
@@ -159,7 +171,7 @@ type CachedFileObject interface {
 
 // NewCachingInodeOperations returns a new CachingInodeOperations backed by
 // a CachedFileObject and its initial unstable attributes.
-func NewCachingInodeOperations(ctx context.Context, backingFile CachedFileObject, uattr fs.UnstableAttr, forcePageCache bool) *CachingInodeOperations {
+func NewCachingInodeOperations(ctx context.Context, backingFile CachedFileObject, uattr fs.UnstableAttr, opts CachingInodeOperationsOptions) *CachingInodeOperations {
 	mfp := pgalloc.MemoryFileProviderFromContext(ctx)
 	if mfp == nil {
 		panic(fmt.Sprintf("context.Context %T lacks non-nil value for key %T", ctx, pgalloc.CtxMemoryFileProvider))
@@ -167,7 +179,7 @@ func NewCachingInodeOperations(ctx context.Context, backingFile CachedFileObject
 	return &CachingInodeOperations{
 		backingFile:    backingFile,
 		mfp:            mfp,
-		forcePageCache: forcePageCache,
+		opts:           opts,
 		attr:           uattr,
 		hostFileMapper: NewHostFileMapper(),
 	}
@@ -763,7 +775,7 @@ func (rw *inodeReadWriter) WriteFromBlocks(srcs safemem.BlockSeq) (uint64, error
 // and memory mappings, and false if c.cache may contain data cached from
 // c.backingFile.
 func (c *CachingInodeOperations) useHostPageCache() bool {
-	return !c.forcePageCache && c.backingFile.FD() >= 0
+	return !c.opts.ForcePageCache && c.backingFile.FD() >= 0
 }
 
 // AddMapping implements memmap.Mappable.AddMapping.
@@ -835,11 +847,15 @@ func (c *CachingInodeOperations) CopyMapping(ctx context.Context, ms memmap.Mapp
 func (c *CachingInodeOperations) Translate(ctx context.Context, required, optional memmap.MappableRange, at usermem.AccessType) ([]memmap.Translation, error) {
 	// Hot path. Avoid defer.
 	if c.useHostPageCache() {
+		mr := optional
+		if c.opts.LimitHostFDTranslation {
+			mr = maxFillRange(required, optional)
+		}
 		return []memmap.Translation{
 			{
-				Source: optional,
+				Source: mr,
 				File:   c,
-				Offset: optional.Start,
+				Offset: mr.Start,
 				Perms:  usermem.AnyAccess,
 			},
 		}, nil

pkg/sentry/fs/fsutil/inode_cached_test.go

@@ -61,7 +61,7 @@ func TestSetPermissions(t *testing.T) {
 	uattr := fs.WithCurrentTime(ctx, fs.UnstableAttr{
 		Perms: fs.FilePermsFromMode(0444),
 	})
-	iops := NewCachingInodeOperations(ctx, noopBackingFile{}, uattr, false /*forcePageCache*/)
+	iops := NewCachingInodeOperations(ctx, noopBackingFile{}, uattr, CachingInodeOperationsOptions{})
 	defer iops.Release()
 
 	perms := fs.FilePermsFromMode(0777)
@@ -150,7 +150,7 @@ func TestSetTimestamps(t *testing.T) {
 				ModificationTime: epoch,
 				StatusChangeTime: epoch,
 			}
-			iops := NewCachingInodeOperations(ctx, noopBackingFile{}, uattr, false /*forcePageCache*/)
+			iops := NewCachingInodeOperations(ctx, noopBackingFile{}, uattr, CachingInodeOperationsOptions{})
 			defer iops.Release()
 
 			if err := iops.SetTimestamps(ctx, nil, test.ts); err != nil {
@@ -188,7 +188,7 @@ func TestTruncate(t *testing.T) {
 	uattr := fs.UnstableAttr{
 		Size: 0,
 	}
-	iops := NewCachingInodeOperations(ctx, noopBackingFile{}, uattr, false /*forcePageCache*/)
+	iops := NewCachingInodeOperations(ctx, noopBackingFile{}, uattr, CachingInodeOperationsOptions{})
 	defer iops.Release()
 
 	if err := iops.Truncate(ctx, nil, uattr.Size); err != nil {
@@ -280,7 +280,7 @@ func TestRead(t *testing.T) {
 	uattr := fs.UnstableAttr{
 		Size: int64(len(buf)),
 	}
-	iops := NewCachingInodeOperations(ctx, newSliceBackingFile(buf), uattr, false /*forcePageCache*/)
+	iops := NewCachingInodeOperations(ctx, newSliceBackingFile(buf), uattr, CachingInodeOperationsOptions{})
 	defer iops.Release()
 
 	// Expect the cache to be initially empty.
@@ -336,7 +336,7 @@ func TestWrite(t *testing.T) {
 	uattr := fs.UnstableAttr{
 		Size: int64(len(buf)),
 	}
-	iops := NewCachingInodeOperations(ctx, newSliceBackingFile(buf), uattr, false /*forcePageCache*/)
+	iops := NewCachingInodeOperations(ctx, newSliceBackingFile(buf), uattr, CachingInodeOperationsOptions{})
 	defer iops.Release()
 
 	// Expect the cache to be initially empty.

pkg/sentry/fs/gofer/fs.go

@@ -54,6 +54,10 @@ const (
 	// sandbox using files backed by the gofer. If set to false, unix sockets
 	// cannot be bound to gofer files without an overlay on top.
 	privateUnixSocketKey = "privateunixsocket"
+
+	// If present, sets CachingInodeOperationsOptions.LimitHostFDTranslation to
+	// true.
+	limitHostFDTranslationKey = "limit_host_fd_translation"
 )
 
 // defaultAname is the default attach name.
@@ -134,12 +138,13 @@ func (f *filesystem) Mount(ctx context.Context, device string, flags fs.MountSou
 
 // opts are parsed 9p mount options.
 type opts struct {
-	fd                int
-	aname             string
-	policy            cachePolicy
-	msize             uint32
-	version           string
-	privateunixsocket bool
+	fd                     int
+	aname                  string
+	policy                 cachePolicy
+	msize                  uint32
+	version                string
+	privateunixsocket      bool
+	limitHostFDTranslation bool
 }
 
 // options parses mount(2) data into structured options.
@@ -237,6 +242,11 @@ func options(data string) (opts, error) {
 		delete(options, privateUnixSocketKey)
 	}
 
+	if _, ok := options[limitHostFDTranslationKey]; ok {
+		o.limitHostFDTranslation = true
+		delete(options, limitHostFDTranslationKey)
+	}
+
 	// Fail to attach if the caller wanted us to do something that we
 	// don't support.
 	if len(options) > 0 {

pkg/sentry/fs/gofer/session.go

@@ -117,6 +117,11 @@ type session struct {
 	// Flags provided to the mount.
 	superBlockFlags fs.MountSourceFlags `state:"wait"`
 
+	// limitHostFDTranslation is the value used for
+	// CachingInodeOperationsOptions.LimitHostFDTranslation for all
+	// CachingInodeOperations created by the session.
+	limitHostFDTranslation bool
+
 	// connID is a unique identifier for the session connection.
 	connID string `state:"wait"`
 
@@ -218,8 +223,11 @@ func newInodeOperations(ctx context.Context, s *session, file contextFile, qid p
 
 	uattr := unstable(ctx, valid, attr, s.mounter, s.client)
 	return sattr, &inodeOperations{
-		fileState:       fileState,
-		cachingInodeOps: fsutil.NewCachingInodeOperations(ctx, fileState, uattr, s.superBlockFlags.ForcePageCache),
+		fileState: fileState,
+		cachingInodeOps: fsutil.NewCachingInodeOperations(ctx, fileState, uattr, fsutil.CachingInodeOperationsOptions{
+			ForcePageCache:         s.superBlockFlags.ForcePageCache,
+			LimitHostFDTranslation: s.limitHostFDTranslation,
+		}),
 	}
 }
 
@@ -242,13 +250,14 @@ func Root(ctx context.Context, dev string, filesystem fs.Filesystem, superBlockF
 
 	// Construct the session.
 	s := session{
-		connID:          dev,
-		msize:           o.msize,
-		version:         o.version,
-		cachePolicy:     o.policy,
-		aname:           o.aname,
-		superBlockFlags: superBlockFlags,
-		mounter:         mounter,
+		connID:                 dev,
+		msize:                  o.msize,
+		version:                o.version,
+		cachePolicy:            o.policy,
+		aname:                  o.aname,
+		superBlockFlags:        superBlockFlags,
+		limitHostFDTranslation: o.limitHostFDTranslation,
+		mounter:                mounter,
 	}
 	s.EnableLeakCheck("gofer.session")
 

pkg/sentry/fs/host/inode.go

@@ -200,8 +200,10 @@ func newInode(ctx context.Context, msrc *fs.MountSource, fd int, saveable bool,
 	// Build the fs.InodeOperations.
 	uattr := unstableAttr(msrc.MountSourceOperations.(*superOperations), &s)
 	iops := &inodeOperations{
-		fileState:       fileState,
-		cachingInodeOps: fsutil.NewCachingInodeOperations(ctx, fileState, uattr, msrc.Flags.ForcePageCache),
+		fileState: fileState,
+		cachingInodeOps: fsutil.NewCachingInodeOperations(ctx, fileState, uattr, fsutil.CachingInodeOperationsOptions{
+			ForcePageCache: msrc.Flags.ForcePageCache,
+		}),
 	}
 
 	// Return the fs.Inode.