Implement StatFS for various VFS2 filesystems.

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

Fixes #3411, #3515.

PiperOrigin-RevId: 329009864

2 files changed, 16 insertions, 1 deletions

diff --git a/pkg/sentry/fsimpl/sys/kcov.go b/pkg/sentry/fsimpl/sys/kcov.go
index 92710d877..73f3d3309 100644
--- a/pkg/sentry/fsimpl/sys/kcov.go
+++ b/pkg/sentry/fsimpl/sys/kcov.go
@@ -39,8 +39,9 @@ func (fs *filesystem) newKcovFile(ctx context.Context, creds *auth.Credentials)
 type kcovInode struct {
 	kernfs.InodeAttrs
 	kernfs.InodeNoopRefCount
-	kernfs.InodeNotSymlink
 	kernfs.InodeNotDirectory
+	kernfs.InodeNotSymlink
+	implStatFS
 }
 
 func (i *kcovInode) Open(ctx context.Context, rp *vfs.ResolvingPath, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
diff --git a/pkg/sentry/fsimpl/sys/sys.go b/pkg/sentry/fsimpl/sys/sys.go
index ea30a4ec2..39952d2d0 100644
--- a/pkg/sentry/fsimpl/sys/sys.go
+++ b/pkg/sentry/fsimpl/sys/sys.go
@@ -163,9 +163,16 @@ func (d *dir) DecRef(context.Context) {
 	d.dirRefs.DecRef(d.Destroy)
 }
 
+// StatFS implements kernfs.Inode.StatFS.
+func (d *dir) StatFS(ctx context.Context, fs *vfs.Filesystem) (linux.Statfs, error) {
+	return vfs.GenericStatFS(linux.SYSFS_MAGIC), nil
+}
+
 // cpuFile implements kernfs.Inode.
 type cpuFile struct {
+	implStatFS
 	kernfs.DynamicBytesFile
+
 	maxCores uint
 }
 
@@ -182,3 +189,10 @@ func (fs *filesystem) newCPUFile(creds *auth.Credentials, maxCores uint, mode li
 	d.Init(c)
 	return d
 }
+
+type implStatFS struct{}
+
+// StatFS implements kernfs.Inode.StatFS.
+func (*implStatFS) StatFS(context.Context, *vfs.Filesystem) (linux.Statfs, error) {
+	return vfs.GenericStatFS(linux.SYSFS_MAGIC), nil
+}