diff options
| -rw-r--r-- | pkg/sentry/fs/file_overlay.go | 68 |
1 files changed, 68 insertions, 0 deletions
diff --git a/pkg/sentry/fs/file_overlay.go b/pkg/sentry/fs/file_overlay.go index c27c5946e..36b2cf75e 100644 --- a/pkg/sentry/fs/file_overlay.go +++ b/pkg/sentry/fs/file_overlay.go @@ -18,6 +18,7 @@ import ( "sync" "gvisor.googlesource.com/gvisor/pkg/log" + "gvisor.googlesource.com/gvisor/pkg/refs" "gvisor.googlesource.com/gvisor/pkg/sentry/arch" "gvisor.googlesource.com/gvisor/pkg/sentry/context" "gvisor.googlesource.com/gvisor/pkg/sentry/memmap" @@ -263,6 +264,34 @@ func (*overlayFileOperations) ConfigureMMap(ctx context.Context, file *File, opt o.copyMu.RLock() defer o.copyMu.RUnlock() + // If there is no lower inode, the overlay will never need to do a + // copy-up, and thus will never need to invalidate any mappings. We can + // call ConfigureMMap directly on the upper file. + if o.lower == nil { + f := file.FileOperations.(*overlayFileOperations) + if err := f.upper.ConfigureMMap(ctx, opts); err != nil { + return err + } + + // ConfigureMMap will set the MappableIdentity to the upper + // file and take a reference on it, but we must also hold a + // reference to the overlay file during the lifetime of the + // Mappable. If we do not do this, the overlay file can be + // Released before the upper file is Released, and we will be + // unable to traverse to the upper file during Save, thus + // preventing us from saving a proper inode mapping for the + // file. + file.IncRef() + id := &overlayMappingIdentity{ + id: opts.MappingIdentity, + overlayFile: file, + } + + // Swap out the old MappingIdentity for the wrapped one. + opts.MappingIdentity = id + return nil + } + if !o.isMappableLocked() { return syserror.ENODEV } @@ -343,3 +372,42 @@ func readdirOne(ctx context.Context, d *Dirent) (map[string]DentAttr, error) { delete(stubSerializer.Entries, "..") return stubSerializer.Entries, nil } + +// overlayMappingIdentity wraps a MappingIdentity, and also holds a reference +// on a file during its lifetime. +type overlayMappingIdentity struct { + refs.AtomicRefCount + id memmap.MappingIdentity + overlayFile *File +} + +// DecRef implements AtomicRefCount.DecRef. +func (omi *overlayMappingIdentity) DecRef() { + omi.AtomicRefCount.DecRefWithDestructor(func() { + omi.overlayFile.DecRef() + omi.id.DecRef() + }) +} + +// DeviceID implements MappingIdentity.DeviceID using the device id from the +// overlayFile. +func (omi *overlayMappingIdentity) DeviceID() uint64 { + return omi.overlayFile.Dirent.Inode.StableAttr.DeviceID +} + +// DeviceID implements MappingIdentity.InodeID using the inode id from the +// overlayFile. +func (omi *overlayMappingIdentity) InodeID() uint64 { + return omi.overlayFile.Dirent.Inode.StableAttr.InodeID +} + +// MappedName implements MappingIdentity.MappedName. +func (omi *overlayMappingIdentity) MappedName(ctx context.Context) string { + name, _ := omi.overlayFile.Dirent.FullName(RootFromContext(ctx)) + return name +} + +// Msync implements MappingIdentity.Msync. +func (omi *overlayMappingIdentity) Msync(ctx context.Context, mr memmap.MappableRange) error { + return omi.id.Msync(ctx, mr) +} |