From e4f093f7b1739b0872774057932704613343db77 Mon Sep 17 00:00:00 2001
From: Ayush Ranjan <ayushranjan@google.com>
Date: Fri, 18 Feb 2022 21:03:18 -0800
Subject: [PATCH] Fix lisafs client bugs for S/R support.

- There was a bug in checking for the availability of STATX_SIZE on restore.
- Make the gofer client resilient to bad open(flags). Like 9P, make lisafs
  default to O_RDONLY when a valid open mode is not available.

PiperOrigin-RevId: 429705352
---
 pkg/sentry/fsimpl/gofer/handle.go       | 9 ++++++---
 pkg/sentry/fsimpl/gofer/save_restore.go | 2 +-
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/pkg/sentry/fsimpl/gofer/handle.go b/pkg/sentry/fsimpl/gofer/handle.go
index 96c7b736d..1643e0ef3 100644
--- a/pkg/sentry/fsimpl/gofer/handle.go
+++ b/pkg/sentry/fsimpl/gofer/handle.go
@@ -18,6 +18,7 @@ import (
 	"golang.org/x/sys/unix"
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/lisafs"
+	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/p9"
 	"gvisor.dev/gvisor/pkg/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/hostfd"
@@ -42,7 +43,7 @@ func openHandle(ctx context.Context, file p9file, read, write, trunc bool) (hand
 	if err != nil {
 		return handle{fd: -1}, err
 	}
-	var flags p9.OpenFlags
+	flags := p9.ReadOnly
 	switch {
 	case read && !write:
 		flags = p9.ReadOnly
@@ -50,6 +51,8 @@ func openHandle(ctx context.Context, file p9file, read, write, trunc bool) (hand
 		flags = p9.WriteOnly
 	case read && write:
 		flags = p9.ReadWrite
+	default:
+		log.Debugf("openHandle called with read = write = false. Falling back to read only FD.")
 	}
 	if trunc {
 		flags |= p9.OpenTruncate
@@ -71,7 +74,7 @@ func openHandle(ctx context.Context, file p9file, read, write, trunc bool) (hand
 
 // Preconditions: read || write.
 func openHandleLisa(ctx context.Context, fdLisa lisafs.ClientFD, read, write, trunc bool) (handle, error) {
-	var flags uint32
+	flags := uint32(unix.O_RDONLY)
 	switch {
 	case read && write:
 		flags = unix.O_RDWR
@@ -80,7 +83,7 @@ func openHandleLisa(ctx context.Context, fdLisa lisafs.ClientFD, read, write, tr
 	case write:
 		flags = unix.O_WRONLY
 	default:
-		panic("tried to open unreadable and unwritable handle")
+		log.Debugf("openHandleLisa called with read = write = false. Falling back to read only FD.")
 	}
 	if trunc {
 		flags |= unix.O_TRUNC
diff --git a/pkg/sentry/fsimpl/gofer/save_restore.go b/pkg/sentry/fsimpl/gofer/save_restore.go
index 01f053999..18f8a1ea5 100644
--- a/pkg/sentry/fsimpl/gofer/save_restore.go
+++ b/pkg/sentry/fsimpl/gofer/save_restore.go
@@ -325,7 +325,7 @@ func (d *dentry) restoreFileLisa(ctx context.Context, inode *lisafs.Inode, opts
 	defer d.metadataMu.Unlock()
 	if d.isRegularFile() {
 		if opts.ValidateFileSizes {
-			if inode.Stat.Mask&linux.STATX_SIZE != 0 {
+			if inode.Stat.Mask&linux.STATX_SIZE == 0 {
 				return vfs.ErrCorruption{fmt.Errorf("gofer.dentry(%q).restoreFile: file size validation failed: file size not available", genericDebugPathname(d))}
 			}
 			if d.size != inode.Stat.Size {