Implement Read in gvisor verity fs

Read is implemented by PRead, with offset obtained from Seek.

PiperOrigin-RevId: 338718587

1 files changed, 14 insertions, 0 deletions

diff --git a/pkg/sentry/fsimpl/verity/verity.go b/pkg/sentry/fsimpl/verity/verity.go
index acc565a10..a0e954efa 100644
--- a/pkg/sentry/fsimpl/verity/verity.go
+++ b/pkg/sentry/fsimpl/verity/verity.go
@@ -499,6 +499,10 @@ type fileDescription struct {
 	// directory that contains the current file/directory. This is only used
 	// if allowRuntimeEnable is set to true.
 	parentMerkleWriter *vfs.FileDescription
+
+	// off is the file offset. off is protected by mu.
+	mu  sync.Mutex `state:"nosave"`
+	off int64
 }
 
 // Release implements vfs.FileDescriptionImpl.Release.
@@ -738,6 +742,16 @@ func (fd *fileDescription) Ioctl(ctx context.Context, uio usermem.IO, args arch.
 	}
 }
 
+// Read implements vfs.FileDescriptionImpl.Read.
+func (fd *fileDescription) Read(ctx context.Context, dst usermem.IOSequence, opts vfs.ReadOptions) (int64, error) {
+	// Implement Read with PRead by setting offset.
+	fd.mu.Lock()
+	n, err := fd.PRead(ctx, dst, fd.off, opts)
+	fd.off += n
+	fd.mu.Unlock()
+	return n, err
+}
+
 // PRead implements vfs.FileDescriptionImpl.PRead.
 func (fd *fileDescription) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts vfs.ReadOptions) (int64, error) {
 	// No need to verify if the file is not enabled yet in