[vfs2][gofer] Fix mmap syscall test.

We were not invalidating mappings when the file size changed in shared mode.
Enabled the syscall test for vfs2.

Updates #2923

PiperOrigin-RevId: 319346569

1 files changed, 6 insertions, 3 deletions

diff --git a/pkg/sentry/fsimpl/gofer/gofer.go b/pkg/sentry/fsimpl/gofer/gofer.go
index 709b5e496..8e74e60a5 100644
--- a/pkg/sentry/fsimpl/gofer/gofer.go
+++ b/pkg/sentry/fsimpl/gofer/gofer.go
@@ -900,6 +900,12 @@ func (d *dentry) setStat(ctx context.Context, creds *auth.Credentials, stat *lin
 	}
 	d.metadataMu.Lock()
 	defer d.metadataMu.Unlock()
+	if stat.Mask&linux.STATX_SIZE != 0 {
+		// The size needs to be changed even when
+		// !d.cachedMetadataAuthoritative() because d.mappings has to be
+		// updated.
+		d.updateFileSizeLocked(stat.Size)
+	}
 	if !d.isSynthetic() {
 		if stat.Mask != 0 {
 			if err := d.file.setAttr(ctx, p9.SetAttrMask{
@@ -961,9 +967,6 @@ func (d *dentry) setStat(ctx context.Context, creds *auth.Credentials, stat *lin
 		stat.Mask |= linux.STATX_MTIME
 	}
 	atomic.StoreInt64(&d.ctime, now)
-	if stat.Mask&linux.STATX_SIZE != 0 {
-		d.updateFileSizeLocked(stat.Size)
-	}
 	return nil
 }