Implement StatFS for various VFS2 filesystems.

This mainly involved enabling kernfs' client filesystems to provide a
StatFS implementation.

Fixes #3411, #3515.

PiperOrigin-RevId: 329009864

7 files changed, 36 insertions, 19 deletions

diff --git a/pkg/sentry/fsimpl/proc/filesystem.go b/pkg/sentry/fsimpl/proc/filesystem.go
index c350ec127..03b5941b9 100644
--- a/pkg/sentry/fsimpl/proc/filesystem.go
+++ b/pkg/sentry/fsimpl/proc/filesystem.go
@@ -121,3 +121,10 @@ func newStaticDir(creds *auth.Credentials, devMajor, devMinor uint32, ino uint64
 type InternalData struct {
 	Cgroups map[string]string
 }
+
+type implStatFS struct{}
+
+// StatFS implements kernfs.Inode.StatFS.
+func (*implStatFS) StatFS(context.Context, *vfs.Filesystem) (linux.Statfs, error) {
+	return vfs.GenericStatFS(linux.PROC_SUPER_MAGIC), nil
+}
diff --git a/pkg/sentry/fsimpl/proc/subtasks.go b/pkg/sentry/fsimpl/proc/subtasks.go
index 01c0efb3a..d57d94dbc 100644
--- a/pkg/sentry/fsimpl/proc/subtasks.go
+++ b/pkg/sentry/fsimpl/proc/subtasks.go
@@ -31,12 +31,13 @@ import (
 //
 // +stateify savable
 type subtasksInode struct {
-	subtasksInodeRefs
-	kernfs.InodeNotSymlink
-	kernfs.InodeDirectoryNoNewChildren
+	implStatFS
+	kernfs.AlwaysValid
 	kernfs.InodeAttrs
+	kernfs.InodeDirectoryNoNewChildren
+	kernfs.InodeNotSymlink
 	kernfs.OrderedChildren
-	kernfs.AlwaysValid
+	subtasksInodeRefs
 
 	locks vfs.FileLocks
 
diff --git a/pkg/sentry/fsimpl/proc/task.go b/pkg/sentry/fsimpl/proc/task.go
index 66b557abd..dbdb5d929 100644
--- a/pkg/sentry/fsimpl/proc/task.go
+++ b/pkg/sentry/fsimpl/proc/task.go
@@ -32,12 +32,13 @@ import (
 //
 // +stateify savable
 type taskInode struct {
-	taskInodeRefs
-	kernfs.InodeNotSymlink
+	implStatFS
+	kernfs.InodeAttrs
 	kernfs.InodeDirectoryNoNewChildren
 	kernfs.InodeNoDynamicLookup
-	kernfs.InodeAttrs
+	kernfs.InodeNotSymlink
 	kernfs.OrderedChildren
+	taskInodeRefs
 
 	locks vfs.FileLocks
 
diff --git a/pkg/sentry/fsimpl/proc/task_fds.go b/pkg/sentry/fsimpl/proc/task_fds.go
index 0527b2de8..3f0d78461 100644
--- a/pkg/sentry/fsimpl/proc/task_fds.go
+++ b/pkg/sentry/fsimpl/proc/task_fds.go
@@ -100,13 +100,14 @@ func (i *fdDir) IterDirents(ctx context.Context, cb vfs.IterDirentsCallback, off
 //
 // +stateify savable
 type fdDirInode struct {
+	fdDir
 	fdDirInodeRefs
-	kernfs.InodeNotSymlink
-	kernfs.InodeDirectoryNoNewChildren
+	implStatFS
+	kernfs.AlwaysValid
 	kernfs.InodeAttrs
+	kernfs.InodeDirectoryNoNewChildren
+	kernfs.InodeNotSymlink
 	kernfs.OrderedChildren
-	kernfs.AlwaysValid
-	fdDir
 }
 
 var _ kernfs.Inode = (*fdDirInode)(nil)
@@ -185,6 +186,7 @@ func (i *fdDirInode) DecRef(context.Context) {
 //
 // +stateify savable
 type fdSymlink struct {
+	implStatFS
 	kernfs.InodeAttrs
 	kernfs.InodeNoopRefCount
 	kernfs.InodeSymlink
@@ -233,13 +235,14 @@ func (s *fdSymlink) Getlink(ctx context.Context, mnt *vfs.Mount) (vfs.VirtualDen
 //
 // +stateify savable
 type fdInfoDirInode struct {
+	fdDir
 	fdInfoDirInodeRefs
-	kernfs.InodeNotSymlink
-	kernfs.InodeDirectoryNoNewChildren
+	implStatFS
+	kernfs.AlwaysValid
 	kernfs.InodeAttrs
+	kernfs.InodeDirectoryNoNewChildren
+	kernfs.InodeNotSymlink
 	kernfs.OrderedChildren
-	kernfs.AlwaysValid
-	fdDir
 }
 
 var _ kernfs.Inode = (*fdInfoDirInode)(nil)
diff --git a/pkg/sentry/fsimpl/proc/task_files.go b/pkg/sentry/fsimpl/proc/task_files.go
index 830b78949..356036b9b 100644
--- a/pkg/sentry/fsimpl/proc/task_files.go
+++ b/pkg/sentry/fsimpl/proc/task_files.go
@@ -648,6 +648,7 @@ func (o *oomScoreAdj) Write(ctx context.Context, src usermem.IOSequence, offset
 //
 // +stateify savable
 type exeSymlink struct {
+	implStatFS
 	kernfs.InodeAttrs
 	kernfs.InodeNoopRefCount
 	kernfs.InodeSymlink
@@ -832,6 +833,7 @@ func (s *namespaceSymlink) Getlink(ctx context.Context, mnt *vfs.Mount) (vfs.Vir
 // namespaceInode is a synthetic inode created to represent a namespace in
 // /proc/[pid]/ns/*.
 type namespaceInode struct {
+	implStatFS
 	kernfs.InodeAttrs
 	kernfs.InodeNoopRefCount
 	kernfs.InodeNotDirectory
diff --git a/pkg/sentry/fsimpl/proc/tasks.go b/pkg/sentry/fsimpl/proc/tasks.go
index 863c4467e..3ea00ab87 100644
--- a/pkg/sentry/fsimpl/proc/tasks.go
+++ b/pkg/sentry/fsimpl/proc/tasks.go
@@ -37,12 +37,13 @@ const (
 //
 // +stateify savable
 type tasksInode struct {
-	tasksInodeRefs
-	kernfs.InodeNotSymlink
-	kernfs.InodeDirectoryNoNewChildren
+	implStatFS
+	kernfs.AlwaysValid
 	kernfs.InodeAttrs
+	kernfs.InodeDirectoryNoNewChildren
+	kernfs.InodeNotSymlink
 	kernfs.OrderedChildren
-	kernfs.AlwaysValid
+	tasksInodeRefs
 
 	locks vfs.FileLocks
 
diff --git a/pkg/sentry/fsimpl/proc/tasks_files.go b/pkg/sentry/fsimpl/proc/tasks_files.go
index 7d8983aa5..8c41729e4 100644
--- a/pkg/sentry/fsimpl/proc/tasks_files.go
+++ b/pkg/sentry/fsimpl/proc/tasks_files.go
@@ -32,6 +32,7 @@ import (
 )
 
 type selfSymlink struct {
+	implStatFS
 	kernfs.InodeAttrs
 	kernfs.InodeNoopRefCount
 	kernfs.InodeSymlink
@@ -74,6 +75,7 @@ func (*selfSymlink) SetStat(context.Context, *vfs.Filesystem, *auth.Credentials,
 }
 
 type threadSelfSymlink struct {
+	implStatFS
 	kernfs.InodeAttrs
 	kernfs.InodeNoopRefCount
 	kernfs.InodeSymlink