Disallow kernfs.Inode.SetStat for readonly inodes

Updates #1195, #1193

PiperOrigin-RevId: 300950993

3 files changed, 18 insertions, 5 deletions

diff --git a/pkg/sentry/fsimpl/kernfs/dynamic_bytes_file.go b/pkg/sentry/fsimpl/kernfs/dynamic_bytes_file.go
index 1c026f4d8..0d27a8867 100644
--- a/pkg/sentry/fsimpl/kernfs/dynamic_bytes_file.go
+++ b/pkg/sentry/fsimpl/kernfs/dynamic_bytes_file.go
@@ -61,9 +61,10 @@ func (f *DynamicBytesFile) Open(rp *vfs.ResolvingPath, vfsd *vfs.Dentry, opts vf
 	return &fd.vfsfd, nil
 }
 
-// SetStat implements Inode.SetStat.
-func (f *DynamicBytesFile) SetStat(*vfs.Filesystem, vfs.SetStatOptions) error {
-	// DynamicBytesFiles are immutable.
+// SetStat implements Inode.SetStat. By default DynamicBytesFile doesn't allow
+// inode attributes to be changed. Override SetStat() making it call
+// f.InodeAttrs to allow it.
+func (*DynamicBytesFile) SetStat(*vfs.Filesystem, vfs.SetStatOptions) error {
 	return syserror.EPERM
 }
 
diff --git a/pkg/sentry/fsimpl/kernfs/inode_impl_util.go b/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
index 94ca3dbdd..4ed41326d 100644
--- a/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
+++ b/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
@@ -228,7 +228,7 @@ func (a *InodeAttrs) Stat(*vfs.Filesystem, vfs.StatOptions) (linux.Statx, error)
 	stat.GID = atomic.LoadUint32(&a.gid)
 	stat.Nlink = atomic.LoadUint32(&a.nlink)
 
-	// TODO: Implement other stat fields like timestamps.
+	// TODO(gvisor.dev/issue/1193): Implement other stat fields like timestamps.
 
 	return stat, nil
 }
@@ -256,7 +256,7 @@ func (a *InodeAttrs) SetStat(_ *vfs.Filesystem, opts vfs.SetStatOptions) error {
 	// Note that not all fields are modifiable. For example, the file type and
 	// inode numbers are immutable after node creation.
 
-	// TODO: Implement other stat fields like timestamps.
+	// TODO(gvisor.dev/issue/1193): Implement other stat fields like timestamps.
 
 	return nil
 }
@@ -555,6 +555,11 @@ func (s *StaticDirectory) Open(rp *vfs.ResolvingPath, vfsd *vfs.Dentry, opts vfs
 	return fd.VFSFileDescription(), nil
 }
 
+// SetStat implements Inode.SetStat not allowing inode attributes to be changed.
+func (*StaticDirectory) SetStat(*vfs.Filesystem, vfs.SetStatOptions) error {
+	return syserror.EPERM
+}
+
 // AlwaysValid partially implements kernfs.inodeDynamicLookup.
 type AlwaysValid struct{}
 
diff --git a/pkg/sentry/fsimpl/kernfs/symlink.go b/pkg/sentry/fsimpl/kernfs/symlink.go
index 0ee7eb9b7..41c5a3099 100644
--- a/pkg/sentry/fsimpl/kernfs/symlink.go
+++ b/pkg/sentry/fsimpl/kernfs/symlink.go
@@ -18,6 +18,8 @@ import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/syserror"
 )
 
 // StaticSymlink provides an Inode implementation for symlinks that point to
@@ -52,3 +54,8 @@ func (s *StaticSymlink) Init(creds *auth.Credentials, ino uint64, target string)
 func (s *StaticSymlink) Readlink(_ context.Context) (string, error) {
 	return s.target, nil
 }
+
+// SetStat implements Inode.SetStat not allowing inode attributes to be changed.
+func (*StaticSymlink) SetStat(*vfs.Filesystem, vfs.SetStatOptions) error {
+	return syserror.EPERM
+}