Force timestamps to update when set via InodeOperations.SetTimestamps.

The gofer's CachingInodeOperations implementation contains an optimization for
the common open-read-close pattern when we have a host FD.  In this case, the
host kernel will update the timestamp for us to a reasonably close time, so we
don't need an extra RPC to the gofer.

However, when the app explicitly sets the timestamps (via futimes or similar)
then we actually DO need to update the timestamps, because the host kernel
won't do it for us.

To fix this, a new boolean `forceSetTimestamps` was added to
CachineInodeOperations.SetMaskedAttributes. It is only set by
gofer.InodeOperations.SetTimestamps.

PiperOrigin-RevId: 272048146

1 files changed, 11 insertions, 4 deletions

diff --git a/pkg/sentry/fs/gofer/inode.go b/pkg/sentry/fs/gofer/inode.go
index 95b064aea..d918d6620 100644
--- a/pkg/sentry/fs/gofer/inode.go
+++ b/pkg/sentry/fs/gofer/inode.go
@@ -215,8 +215,8 @@ func (i *inodeFileState) WriteFromBlocksAt(ctx context.Context, srcs safemem.Blo
 }
 
 // SetMaskedAttributes implements fsutil.CachedFileObject.SetMaskedAttributes.
-func (i *inodeFileState) SetMaskedAttributes(ctx context.Context, mask fs.AttrMask, attr fs.UnstableAttr) error {
-	if i.skipSetAttr(mask) {
+func (i *inodeFileState) SetMaskedAttributes(ctx context.Context, mask fs.AttrMask, attr fs.UnstableAttr, forceSetTimestamps bool) error {
+	if i.skipSetAttr(mask, forceSetTimestamps) {
 		return nil
 	}
 	as, ans := attr.AccessTime.Unix()
@@ -251,13 +251,14 @@ func (i *inodeFileState) SetMaskedAttributes(ctx context.Context, mask fs.AttrMa
 // when:
 //   - Mask is empty
 //   - Mask contains only attributes that cannot be set in the gofer
-//   - Mask contains only atime and/or mtime, and host FD exists
+//   - forceSetTimestamps is false and mask contains only atime and/or mtime
+//     and host FD exists
 //
 // Updates to atime and mtime can be skipped because cached value will be
 // "close enough" to host value, given that operation went directly to host FD.
 // Skipping atime updates is particularly important to reduce the number of
 // operations sent to the Gofer for readonly files.
-func (i *inodeFileState) skipSetAttr(mask fs.AttrMask) bool {
+func (i *inodeFileState) skipSetAttr(mask fs.AttrMask, forceSetTimestamps bool) bool {
 	// First remove attributes that cannot be updated.
 	cpy := mask
 	cpy.Type = false
@@ -277,6 +278,12 @@ func (i *inodeFileState) skipSetAttr(mask fs.AttrMask) bool {
 		return false
 	}
 
+	// If forceSetTimestamps was passed, then we cannot skip.
+	if forceSetTimestamps {
+		return false
+	}
+
+	// Skip if we have a host FD.
 	i.handlesMu.RLock()
 	defer i.handlesMu.RUnlock()
 	return (i.readHandles != nil && i.readHandles.Host != nil) ||