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-rw-r--r--pkg/sentry/fs/README.md12
-rw-r--r--pkg/sentry/fs/dirent.go2
-rw-r--r--pkg/sentry/fs/file_overlay_test.go70
-rw-r--r--pkg/sentry/fs/gofer/session.go6
-rw-r--r--pkg/sentry/fs/inode_overlay.go43
-rw-r--r--pkg/sentry/fs/inode_overlay_test.go123
-rw-r--r--pkg/sentry/fs/mock.go2
-rw-r--r--pkg/sentry/fs/mount.go28
-rw-r--r--pkg/sentry/fs/mount_overlay.go39
-rw-r--r--pkg/sentry/fs/overlay.go8
-rw-r--r--pkg/sentry/fs/tty/fs.go2
11 files changed, 279 insertions, 56 deletions
diff --git a/pkg/sentry/fs/README.md b/pkg/sentry/fs/README.md
index 76638cdae..7680187f4 100644
--- a/pkg/sentry/fs/README.md
+++ b/pkg/sentry/fs/README.md
@@ -193,6 +193,18 @@ interface. It multiplexes between upper and lower directory memory mappings and
stores a copy of memory references so they can be transferred to the upper
directory `fs.Mappable` when the file is copied up.
+The lower filesystem in an overlay may contain another (nested) overlay, but the
+upper filesystem may not contain another overlay. In other words, nested
+overlays form a tree structure that only allows branching in the lower
+filesystem.
+
+Caching decisions in the overlay are delegated to the upper filesystem, meaning
+that the Keep and Revalidate methods on the overlay return the same values as
+the upper filesystem. A small wrinkle is that the lower filesystem is not
+allowed to return `true` from Revalidate, as the overlay can not reload inodes
+from the lower filesystem. A lower filesystem that does return `true` from
+Revalidate will trigger a panic.
+
The `fs.Inode` also holds a reference to a `fs.MountedFilesystem` that
normalizes across the mounted filesystem state of the upper and lower
directories.
diff --git a/pkg/sentry/fs/dirent.go b/pkg/sentry/fs/dirent.go
index 821cc5789..f81ad5792 100644
--- a/pkg/sentry/fs/dirent.go
+++ b/pkg/sentry/fs/dirent.go
@@ -503,7 +503,7 @@ func (d *Dirent) walk(ctx context.Context, root *Dirent, name string, walkMayUnl
//
// We never allow the file system to revalidate mounts, that could cause them
// to unexpectedly drop out before umount.
- if cd.mounted || !cd.Inode.MountSource.Revalidate(ctx, cd) {
+ if cd.mounted || !cd.Inode.MountSource.Revalidate(ctx, cd.Inode) {
// Good to go. This is the fast-path.
return cd, nil
}
diff --git a/pkg/sentry/fs/file_overlay_test.go b/pkg/sentry/fs/file_overlay_test.go
index 407ba8562..38762d8a1 100644
--- a/pkg/sentry/fs/file_overlay_test.go
+++ b/pkg/sentry/fs/file_overlay_test.go
@@ -21,6 +21,7 @@ import (
"gvisor.googlesource.com/gvisor/pkg/sentry/context"
"gvisor.googlesource.com/gvisor/pkg/sentry/context/contexttest"
"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
+ ramfstest "gvisor.googlesource.com/gvisor/pkg/sentry/fs/ramfs/test"
)
func TestReaddir(t *testing.T) {
@@ -48,7 +49,7 @@ func TestReaddir(t *testing.T) {
{name: "a"},
{name: "b"},
}, nil), /* lower */
- ),
+ false /* revalidate */),
names: []string{".", "..", "a", "b"},
},
{
@@ -59,7 +60,7 @@ func TestReaddir(t *testing.T) {
{name: "b"},
}, nil), /* upper */
nil, /* lower */
- ),
+ false /* revalidate */),
names: []string{".", "..", "a", "b"},
},
{
@@ -67,11 +68,11 @@ func TestReaddir(t *testing.T) {
dir: fs.NewTestOverlayDir(ctx,
newTestRamfsDir(ctx, []dirContent{
{name: "a"},
- }, nil), /* lower */
+ }, nil), /* upper */
newTestRamfsDir(ctx, []dirContent{
{name: "b"},
}, nil), /* lower */
- ),
+ false /* revalidate */),
names: []string{".", "..", "a", "b"},
},
{
@@ -79,11 +80,11 @@ func TestReaddir(t *testing.T) {
dir: fs.NewTestOverlayDir(ctx,
newTestRamfsDir(ctx, []dirContent{
{name: "a"},
- }, []string{"b"}), /* lower */
+ }, []string{"b"}), /* upper */
newTestRamfsDir(ctx, []dirContent{
{name: "c"},
}, nil), /* lower */
- ),
+ false /* revalidate */),
names: []string{".", "..", "a", "c"},
},
{
@@ -91,12 +92,12 @@ func TestReaddir(t *testing.T) {
dir: fs.NewTestOverlayDir(ctx,
newTestRamfsDir(ctx, []dirContent{
{name: "a"},
- }, []string{"b"}), /* lower */
+ }, []string{"b"}), /* upper */
newTestRamfsDir(ctx, []dirContent{
{name: "b"}, /* will be masked */
{name: "c"},
}, nil), /* lower */
- ),
+ false /* revalidate */),
names: []string{".", "..", "a", "c"},
},
} {
@@ -120,6 +121,59 @@ func TestReaddir(t *testing.T) {
}
}
+func TestReaddirRevalidation(t *testing.T) {
+ ctx := contexttest.Context(t)
+ ctx = &rootContext{
+ Context: ctx,
+ root: fs.NewDirent(newTestRamfsDir(ctx, nil, nil), "root"),
+ }
+
+ // Create an overlay with two directories, each with one file.
+ upper := newTestRamfsDir(ctx, []dirContent{{name: "a"}}, nil)
+ lower := newTestRamfsDir(ctx, []dirContent{{name: "b"}}, nil)
+ overlay := fs.NewTestOverlayDir(ctx, upper, lower, true /* revalidate */)
+
+ // Get a handle to the dirent in the upper filesystem so that we can
+ // modify it without going through the dirent.
+ upperDir := upper.InodeOperations.(*dir).InodeOperations.(*ramfstest.Dir)
+
+ // Check that overlay returns the files from both upper and lower.
+ openDir, err := overlay.GetFile(ctx, fs.NewDirent(overlay, "stub"), fs.FileFlags{Read: true})
+ if err != nil {
+ t.Fatalf("GetFile got error %v, want nil", err)
+ }
+ ser := &fs.CollectEntriesSerializer{}
+ if err := openDir.Readdir(ctx, ser); err != nil {
+ t.Fatalf("Readdir got error %v, want nil", err)
+ }
+ got, want := ser.Order, []string{".", "..", "a", "b"}
+ if !reflect.DeepEqual(got, want) {
+ t.Errorf("Readdir got names %v, want %v", got, want)
+ }
+
+ // Remove "a" from the upper and add "c".
+ if err := upperDir.Remove(ctx, upper, "a"); err != nil {
+ t.Fatalf("error removing child: %v", err)
+ }
+ upperDir.AddChild(ctx, "c", fs.NewInode(ramfstest.NewFile(ctx, fs.FilePermissions{}),
+ upper.MountSource, fs.StableAttr{Type: fs.RegularFile}))
+
+ // Seek to beginning of the directory and do the readdir again.
+ if _, err := openDir.Seek(ctx, fs.SeekSet, 0); err != nil {
+ t.Fatalf("error seeking to beginning of dir: %v", err)
+ }
+ ser = &fs.CollectEntriesSerializer{}
+ if err := openDir.Readdir(ctx, ser); err != nil {
+ t.Fatalf("Readdir got error %v, want nil", err)
+ }
+
+ // Readdir should return the updated children.
+ got, want = ser.Order, []string{".", "..", "b", "c"}
+ if !reflect.DeepEqual(got, want) {
+ t.Errorf("Readdir got names %v, want %v", got, want)
+ }
+}
+
type rootContext struct {
context.Context
root *fs.Dirent
diff --git a/pkg/sentry/fs/gofer/session.go b/pkg/sentry/fs/gofer/session.go
index bfb1154dc..eeb9087e9 100644
--- a/pkg/sentry/fs/gofer/session.go
+++ b/pkg/sentry/fs/gofer/session.go
@@ -145,12 +145,12 @@ func (s *session) Destroy() {
s.conn.Close()
}
-// Revalidate returns true if the cache policy is does not allow for VFS caching.
-func (s *session) Revalidate(ctx context.Context, d *fs.Dirent) bool {
+// Revalidate implements MountSource.Revalidate.
+func (s *session) Revalidate(ctx context.Context, i *fs.Inode) bool {
return s.cachePolicy.revalidateDirent()
}
-// TakeRefs takes an extra reference on dirent if possible.
+// Keep implements MountSource.Keep.
func (s *session) Keep(d *fs.Dirent) bool {
return s.cachePolicy.keepDirent(d.Inode)
}
diff --git a/pkg/sentry/fs/inode_overlay.go b/pkg/sentry/fs/inode_overlay.go
index 543db9ac7..34e62a4a2 100644
--- a/pkg/sentry/fs/inode_overlay.go
+++ b/pkg/sentry/fs/inode_overlay.go
@@ -57,6 +57,10 @@ func overlayLookup(ctx context.Context, parent *overlayEntry, inode *Inode, name
var upperInode *Inode
var lowerInode *Inode
+ // We must remember whether the upper fs returned a negative dirent,
+ // because it is only safe to return one if the upper did.
+ var negativeUpperChild bool
+
// Does the parent directory exist in the upper file system?
if parent.upper != nil {
// First check if a file object exists in the upper file system.
@@ -70,7 +74,9 @@ func overlayLookup(ctx context.Context, parent *overlayEntry, inode *Inode, name
return nil, err
}
if child != nil {
- if !child.IsNegative() {
+ if child.IsNegative() {
+ negativeUpperChild = true
+ } else {
upperInode = child.Inode
upperInode.IncRef()
}
@@ -81,7 +87,18 @@ func overlayLookup(ctx context.Context, parent *overlayEntry, inode *Inode, name
if overlayHasWhiteout(parent.upper, name) {
if upperInode == nil {
parent.copyMu.RUnlock()
- return NewNegativeDirent(name), nil
+ if negativeUpperChild {
+ // If the upper fs returnd a negative
+ // Dirent, then the upper is OK with
+ // that negative Dirent being cached in
+ // the Dirent tree, so we can return
+ // one from the overlay.
+ return NewNegativeDirent(name), nil
+ }
+ // Upper fs is not OK with a negative Dirent
+ // being cached in the Dirent tree, so don't
+ // return one.
+ return nil, syserror.ENOENT
}
entry, err := newOverlayEntry(ctx, upperInode, nil, false)
if err != nil {
@@ -127,9 +144,14 @@ func overlayLookup(ctx context.Context, parent *overlayEntry, inode *Inode, name
// Was all of this for naught?
if upperInode == nil && lowerInode == nil {
- // Return a negative Dirent indicating that nothing was found.
parent.copyMu.RUnlock()
- return NewNegativeDirent(name), nil
+ // We can only return a negative dirent if the upper returned
+ // one as well. See comments above regarding negativeUpperChild
+ // for more info.
+ if negativeUpperChild {
+ return NewNegativeDirent(name), nil
+ }
+ return nil, syserror.ENOENT
}
// Did we find a lower Inode? Remember this because we may decide we don't
@@ -568,10 +590,19 @@ func overlayHandleOps(o *overlayEntry) HandleOperations {
}
// NewTestOverlayDir returns an overlay Inode for tests.
-func NewTestOverlayDir(ctx context.Context, upper *Inode, lower *Inode) *Inode {
+//
+// If `revalidate` is true, then the upper filesystem will require
+// revalidation.
+func NewTestOverlayDir(ctx context.Context, upper, lower *Inode, revalidate bool) *Inode {
fs := &overlayFilesystem{}
+ var upperMsrc *MountSource
+ if revalidate {
+ upperMsrc = NewRevalidatingMountSource(fs, MountSourceFlags{})
+ } else {
+ upperMsrc = NewNonCachingMountSource(fs, MountSourceFlags{})
+ }
msrc := NewMountSource(&overlayMountSourceOperations{
- upper: NewNonCachingMountSource(fs, MountSourceFlags{}),
+ upper: upperMsrc,
lower: NewNonCachingMountSource(fs, MountSourceFlags{}),
}, fs, MountSourceFlags{})
overlay := &overlayEntry{
diff --git a/pkg/sentry/fs/inode_overlay_test.go b/pkg/sentry/fs/inode_overlay_test.go
index 684d54bd2..a7be9d040 100644
--- a/pkg/sentry/fs/inode_overlay_test.go
+++ b/pkg/sentry/fs/inode_overlay_test.go
@@ -35,7 +35,6 @@ func TestLookup(t *testing.T) {
name string
// Want from lookup.
- err error
found bool
hasUpper bool
hasLower bool
@@ -50,7 +49,7 @@ func TestLookup(t *testing.T) {
dir: false,
},
}, nil), /* lower */
- ),
+ false /* revalidate */),
name: "a",
found: true,
hasUpper: false,
@@ -66,7 +65,7 @@ func TestLookup(t *testing.T) {
},
}, nil), /* upper */
nil, /* lower */
- ),
+ false /* revalidate */),
name: "a",
found: true,
hasUpper: true,
@@ -87,7 +86,7 @@ func TestLookup(t *testing.T) {
dir: false,
},
}, nil), /* lower */
- ),
+ false /* revalidate */),
name: "a",
found: true,
hasUpper: false,
@@ -108,7 +107,7 @@ func TestLookup(t *testing.T) {
dir: false,
},
}, nil), /* lower */
- ),
+ false /* revalidate */),
name: "a",
found: true,
hasUpper: true,
@@ -129,7 +128,7 @@ func TestLookup(t *testing.T) {
dir: false,
},
}, nil), /* lower */
- ),
+ false /* revalidate */),
name: "a",
found: true,
hasUpper: true,
@@ -150,7 +149,7 @@ func TestLookup(t *testing.T) {
dir: true,
},
}, nil), /* lower */
- ),
+ false /* revalidate */),
name: "a",
found: true,
hasUpper: true,
@@ -166,7 +165,7 @@ func TestLookup(t *testing.T) {
dir: false,
},
}, nil), /* lower */
- ),
+ false /* revalidate */),
name: "a",
found: false,
hasUpper: false,
@@ -182,7 +181,7 @@ func TestLookup(t *testing.T) {
dir: false,
},
}, nil), /* lower */
- ),
+ false /* revalidate */),
name: "a",
found: true,
hasUpper: false,
@@ -191,13 +190,14 @@ func TestLookup(t *testing.T) {
} {
t.Run(test.desc, func(t *testing.T) {
dirent, err := test.dir.Lookup(ctx, test.name)
- if err != test.err {
- t.Fatalf("lookup got error %v, want %v", err, test.err)
- }
- if test.found && dirent.IsNegative() {
- t.Fatalf("lookup expected to find %q, got negative dirent", test.name)
+ if test.found && (err == syserror.ENOENT || dirent.IsNegative()) {
+ t.Fatalf("lookup %q expected to find positive dirent, got dirent %v err %v", test.name, dirent, err)
}
if !test.found {
+ if err != syserror.ENOENT && !dirent.IsNegative() {
+ t.Errorf("lookup %q expected to return ENOENT or negative dirent, got dirent %v err %v", test.name, dirent, err)
+ }
+ // Nothing more to check.
return
}
if hasUpper := dirent.Inode.TestHasUpperFS(); hasUpper != test.hasUpper {
@@ -210,6 +210,95 @@ func TestLookup(t *testing.T) {
}
}
+func TestLookupRevalidation(t *testing.T) {
+ // File name used in the tests.
+ fileName := "foofile"
+ ctx := contexttest.Context(t)
+ for _, tc := range []struct {
+ // Test description.
+ desc string
+
+ // Upper and lower fs for the overlay.
+ upper *fs.Inode
+ lower *fs.Inode
+
+ // Whether the upper requires revalidation.
+ revalidate bool
+
+ // Whether we should get the same dirent on second lookup.
+ wantSame bool
+ }{
+ {
+ desc: "file from upper with no revalidation",
+ upper: newTestRamfsDir(ctx, []dirContent{{name: fileName}}, nil),
+ lower: newTestRamfsDir(ctx, nil, nil),
+ revalidate: false,
+ wantSame: true,
+ },
+ {
+ desc: "file from upper with revalidation",
+ upper: newTestRamfsDir(ctx, []dirContent{{name: fileName}}, nil),
+ lower: newTestRamfsDir(ctx, nil, nil),
+ revalidate: true,
+ wantSame: false,
+ },
+ {
+ desc: "file from lower with no revalidation",
+ upper: newTestRamfsDir(ctx, nil, nil),
+ lower: newTestRamfsDir(ctx, []dirContent{{name: fileName}}, nil),
+ revalidate: false,
+ wantSame: true,
+ },
+ {
+ desc: "file from lower with revalidation",
+ upper: newTestRamfsDir(ctx, nil, nil),
+ lower: newTestRamfsDir(ctx, []dirContent{{name: fileName}}, nil),
+ revalidate: true,
+ // The file does not exist in the upper, so we do not
+ // need to revalidate it.
+ wantSame: true,
+ },
+ {
+ desc: "file from upper and lower with no revalidation",
+ upper: newTestRamfsDir(ctx, []dirContent{{name: fileName}}, nil),
+ lower: newTestRamfsDir(ctx, []dirContent{{name: fileName}}, nil),
+ revalidate: false,
+ wantSame: true,
+ },
+ {
+ desc: "file from upper and lower with revalidation",
+ upper: newTestRamfsDir(ctx, []dirContent{{name: fileName}}, nil),
+ lower: newTestRamfsDir(ctx, []dirContent{{name: fileName}}, nil),
+ revalidate: true,
+ wantSame: false,
+ },
+ } {
+ t.Run(tc.desc, func(t *testing.T) {
+ root := fs.NewDirent(newTestRamfsDir(ctx, nil, nil), "root")
+ ctx = &rootContext{
+ Context: ctx,
+ root: root,
+ }
+ overlay := fs.NewDirent(fs.NewTestOverlayDir(ctx, tc.upper, tc.lower, tc.revalidate), "overlay")
+ // Lookup the file twice through the overlay.
+ first, err := overlay.Walk(ctx, root, fileName)
+ if err != nil {
+ t.Fatalf("overlay.Walk(%q) failed: %v", fileName, err)
+ }
+ second, err := overlay.Walk(ctx, root, fileName)
+ if err != nil {
+ t.Fatalf("overlay.Walk(%q) failed: %v", fileName, err)
+ }
+
+ if tc.wantSame && first != second {
+ t.Errorf("dirent lookup got different dirents, wanted same\nfirst=%+v\nsecond=%+v", first, second)
+ } else if !tc.wantSame && first == second {
+ t.Errorf("dirent lookup got the same dirent, wanted different: %+v", first)
+ }
+ })
+ }
+}
+
type dir struct {
fs.InodeOperations
@@ -231,6 +320,10 @@ type dirContent struct {
dir bool
}
+func newTestRamfsInode(ctx context.Context, msrc *fs.MountSource) *fs.Inode {
+ return fs.NewInode(ramfstest.NewFile(ctx, fs.FilePermissions{}), msrc, fs.StableAttr{Type: fs.RegularFile})
+}
+
func newTestRamfsDir(ctx context.Context, contains []dirContent, negative []string) *fs.Inode {
msrc := fs.NewCachingMountSource(nil, fs.MountSourceFlags{})
contents := make(map[string]*fs.Inode)
@@ -238,7 +331,7 @@ func newTestRamfsDir(ctx context.Context, contains []dirContent, negative []stri
if c.dir {
contents[c.name] = newTestRamfsDir(ctx, nil, nil)
} else {
- contents[c.name] = fs.NewInode(ramfstest.NewFile(ctx, fs.FilePermissions{}), msrc, fs.StableAttr{Type: fs.RegularFile})
+ contents[c.name] = newTestRamfsInode(ctx, msrc)
}
}
dops := ramfstest.NewDir(ctx, contents, fs.FilePermissions{
diff --git a/pkg/sentry/fs/mock.go b/pkg/sentry/fs/mock.go
index dc82a2002..89a0103ba 100644
--- a/pkg/sentry/fs/mock.go
+++ b/pkg/sentry/fs/mock.go
@@ -68,7 +68,7 @@ func NewMockMountSource(cache *DirentCache) *MountSource {
}
// Revalidate implements fs.MountSourceOperations.Revalidate.
-func (n *MockMountSourceOps) Revalidate(context.Context, *Dirent) bool {
+func (n *MockMountSourceOps) Revalidate(context.Context, *Inode) bool {
return n.revalidate
}
diff --git a/pkg/sentry/fs/mount.go b/pkg/sentry/fs/mount.go
index c72372929..455f5b35c 100644
--- a/pkg/sentry/fs/mount.go
+++ b/pkg/sentry/fs/mount.go
@@ -27,10 +27,10 @@ import (
// DirentOperations provide file systems greater control over how long a Dirent stays pinned
// in core. Implementations must not take Dirent.mu.
type DirentOperations interface {
- // Revalidate returns true if the Dirent is stale and its
+ // Revalidate returns true if the Inode is stale and its
// InodeOperations needs to be reloaded. Revalidate will never be
- // called on a Dirent that is mounted.
- Revalidate(ctx context.Context, dirent *Dirent) bool
+ // called on a Inode that is mounted.
+ Revalidate(ctx context.Context, inode *Inode) bool
// Keep returns true if the Dirent should be kept in memory for as long
// as possible beyond any active references.
@@ -249,7 +249,8 @@ func (msrc *MountSource) FlushDirentRefs() {
// aggressively. Filesystem may be nil if there is no backing filesystem.
func NewCachingMountSource(filesystem Filesystem, flags MountSourceFlags) *MountSource {
return NewMountSource(&SimpleMountSourceOperations{
- keep: true,
+ keep: true,
+ revalidate: false,
}, filesystem, flags)
}
@@ -257,7 +258,17 @@ func NewCachingMountSource(filesystem Filesystem, flags MountSourceFlags) *Mount
// Filesystem may be nil if there is no backing filesystem.
func NewNonCachingMountSource(filesystem Filesystem, flags MountSourceFlags) *MountSource {
return NewMountSource(&SimpleMountSourceOperations{
- keep: false,
+ keep: false,
+ revalidate: false,
+ }, filesystem, flags)
+}
+
+// NewRevalidatingMountSource returns a generic mount that will cache dirents,
+// but will revalidate them on each lookup.
+func NewRevalidatingMountSource(filesystem Filesystem, flags MountSourceFlags) *MountSource {
+ return NewMountSource(&SimpleMountSourceOperations{
+ keep: true,
+ revalidate: true,
}, filesystem, flags)
}
@@ -265,12 +276,13 @@ func NewNonCachingMountSource(filesystem Filesystem, flags MountSourceFlags) *Mo
//
// +stateify savable
type SimpleMountSourceOperations struct {
- keep bool
+ keep bool
+ revalidate bool
}
// Revalidate implements MountSourceOperations.Revalidate.
-func (*SimpleMountSourceOperations) Revalidate(context.Context, *Dirent) bool {
- return false
+func (smo *SimpleMountSourceOperations) Revalidate(context.Context, *Inode) bool {
+ return smo.revalidate
}
// Keep implements MountSourceOperations.Keep.
diff --git a/pkg/sentry/fs/mount_overlay.go b/pkg/sentry/fs/mount_overlay.go
index d135e8a37..9fa87c10f 100644
--- a/pkg/sentry/fs/mount_overlay.go
+++ b/pkg/sentry/fs/mount_overlay.go
@@ -14,10 +14,13 @@
package fs
-import "gvisor.googlesource.com/gvisor/pkg/sentry/context"
+import (
+ "gvisor.googlesource.com/gvisor/pkg/sentry/context"
+)
// overlayMountSourceOperations implements MountSourceOperations for an overlay
-// mount point.
+// mount point. The upper filesystem determines the caching behavior of the
+// overlay.
//
// +stateify savable
type overlayMountSourceOperations struct {
@@ -34,19 +37,33 @@ func newOverlayMountSource(upper, lower *MountSource, flags MountSourceFlags) *M
}, &overlayFilesystem{}, flags)
}
-// Revalidate panics if the upper or lower MountSource require that dirent be
-// revalidated. Otherwise always returns false.
-func (o *overlayMountSourceOperations) Revalidate(ctx context.Context, dirent *Dirent) bool {
- if o.upper.Revalidate(ctx, dirent) || o.lower.Revalidate(ctx, dirent) {
- panic("an overlay cannot revalidate file objects")
+// Revalidate implements MountSourceOperations.Revalidate for an overlay by
+// delegating to the upper filesystem's Revalidate method. We cannot reload
+// files from the lower filesystem, so we panic if the lower filesystem's
+// Revalidate method returns true.
+func (o *overlayMountSourceOperations) Revalidate(ctx context.Context, inode *Inode) bool {
+ if inode.overlay == nil {
+ panic("overlay cannot revalidate inode that is not an overlay")
}
- return false
+
+ // Should we bother checking this, or just ignore?
+ if inode.overlay.lower != nil && o.lower.Revalidate(ctx, inode.overlay.lower) {
+ panic("an overlay cannot revalidate file objects from the lower fs")
+ }
+
+ if inode.overlay.upper == nil {
+ // Nothing to revalidate.
+ return false
+ }
+
+ // Does the upper require revalidation?
+ return o.upper.Revalidate(ctx, inode.overlay.upper)
}
-// Keep returns true if either upper or lower MountSource require that the
-// dirent be kept in memory.
+// Keep implements MountSourceOperations by delegating to the upper
+// filesystem's Keep method.
func (o *overlayMountSourceOperations) Keep(dirent *Dirent) bool {
- return o.upper.Keep(dirent) || o.lower.Keep(dirent)
+ return o.upper.Keep(dirent)
}
// ResetInodeMappings propagates the call to both upper and lower MountSource.
diff --git a/pkg/sentry/fs/overlay.go b/pkg/sentry/fs/overlay.go
index af13dc8c7..5a30af419 100644
--- a/pkg/sentry/fs/overlay.go
+++ b/pkg/sentry/fs/overlay.go
@@ -88,10 +88,11 @@ func isXattrOverlay(name string) bool {
// Preconditions:
//
// - upper and lower must be non-nil.
+// - upper must not be an overlay.
// - lower should not expose character devices, pipes, or sockets, because
// copying up these types of files is not supported.
-// - upper and lower must not require that file objects be revalidated.
-// - upper and lower must not have dynamic file/directory content.
+// - lower must not require that file objects be revalidated.
+// - lower must not have dynamic file/directory content.
func NewOverlayRoot(ctx context.Context, upper *Inode, lower *Inode, flags MountSourceFlags) (*Inode, error) {
if !IsDir(upper.StableAttr) {
return nil, fmt.Errorf("upper Inode is not a directory")
@@ -99,6 +100,9 @@ func NewOverlayRoot(ctx context.Context, upper *Inode, lower *Inode, flags Mount
if !IsDir(lower.StableAttr) {
return nil, fmt.Errorf("lower Inode is not a directory")
}
+ if upper.overlay != nil {
+ return nil, fmt.Errorf("cannot nest overlay in upper file of another overlay")
+ }
msrc := newOverlayMountSource(upper.MountSource, lower.MountSource, flags)
overlay, err := newOverlayEntry(ctx, upper, lower, true)
diff --git a/pkg/sentry/fs/tty/fs.go b/pkg/sentry/fs/tty/fs.go
index e28635607..fe7da05b5 100644
--- a/pkg/sentry/fs/tty/fs.go
+++ b/pkg/sentry/fs/tty/fs.go
@@ -82,7 +82,7 @@ type superOperations struct{}
// Slave entries are dropped from dir when their master is closed, so an
// existing slave Dirent in the tree is not sufficient to guarantee that it
// still exists on the filesystem.
-func (superOperations) Revalidate(context.Context, *fs.Dirent) bool {
+func (superOperations) Revalidate(context.Context, *fs.Inode) bool {
return true
}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-28 22:56:31 +0000