diff options
Diffstat (limited to 'pkg/sentry/fs/file_overlay.go')
| -rw-r--r-- | pkg/sentry/fs/file_overlay.go | 79 |
1 files changed, 51 insertions, 28 deletions
diff --git a/pkg/sentry/fs/file_overlay.go b/pkg/sentry/fs/file_overlay.go index 948ce9c6f..273de1e14 100644 --- a/pkg/sentry/fs/file_overlay.go +++ b/pkg/sentry/fs/file_overlay.go @@ -17,7 +17,6 @@ package fs 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" @@ -222,31 +221,50 @@ func (f *overlayFileOperations) IterateDir(ctx context.Context, dirCtx *DirCtx, return offset + n, err } -// Read implements FileOperations.Read. -func (f *overlayFileOperations) Read(ctx context.Context, file *File, dst usermem.IOSequence, offset int64) (int64, error) { - o := file.Dirent.Inode.overlay +// onTop performs the given operation on the top-most available layer. +func (f *overlayFileOperations) onTop(ctx context.Context, file *File, fn func(*File, FileOperations) error) error { + file.Dirent.Inode.overlay.copyMu.RLock() + defer file.Dirent.Inode.overlay.copyMu.RUnlock() - o.copyMu.RLock() - defer o.copyMu.RUnlock() + // Only lower layer is available. + if file.Dirent.Inode.overlay.upper == nil { + return fn(f.lower, f.lower.FileOperations) + } - if o.upper != nil { - // We may need to acquire an open file handle to read from if - // copy up has occurred. Otherwise we risk reading from the - // wrong source. - f.upperMu.Lock() - if f.upper == nil { - var err error - f.upper, err = overlayFile(ctx, o.upper, file.Flags()) - if err != nil { - f.upperMu.Unlock() - log.Warningf("failed to acquire handle with flags %v: %v", file.Flags(), err) - return 0, syserror.EIO - } + f.upperMu.Lock() + if f.upper == nil { + upper, err := overlayFile(ctx, file.Dirent.Inode.overlay.upper, file.Flags()) + if err != nil { + // Something very wrong; return a generic filesystem + // error to avoid propagating internals. + f.upperMu.Unlock() + return syserror.EIO } - f.upperMu.Unlock() - return f.upper.FileOperations.Read(ctx, f.upper, dst, offset) + + // Save upper file. + f.upper = upper } - return f.lower.FileOperations.Read(ctx, f.lower, dst, offset) + f.upperMu.Unlock() + + return fn(f.upper, f.upper.FileOperations) +} + +// Read implements FileOperations.Read. +func (f *overlayFileOperations) Read(ctx context.Context, file *File, dst usermem.IOSequence, offset int64) (n int64, err error) { + err = f.onTop(ctx, file, func(file *File, ops FileOperations) error { + n, err = ops.Read(ctx, file, dst, offset) + return err // Will overwrite itself. + }) + return +} + +// WriteTo implements FileOperations.WriteTo. +func (f *overlayFileOperations) WriteTo(ctx context.Context, file *File, dst *File, opts SpliceOpts) (n int64, err error) { + err = f.onTop(ctx, file, func(file *File, ops FileOperations) error { + n, err = ops.WriteTo(ctx, file, dst, opts) + return err // Will overwrite itself. + }) + return } // Write implements FileOperations.Write. @@ -257,15 +275,20 @@ func (f *overlayFileOperations) Write(ctx context.Context, file *File, src userm return f.upper.FileOperations.Write(ctx, f.upper, src, offset) } +// ReadFrom implements FileOperations.ReadFrom. +func (f *overlayFileOperations) ReadFrom(ctx context.Context, file *File, src *File, opts SpliceOpts) (n int64, err error) { + // See above; f.upper must be non-nil. + return f.upper.FileOperations.ReadFrom(ctx, f.upper, src, opts) +} + // Fsync implements FileOperations.Fsync. -func (f *overlayFileOperations) Fsync(ctx context.Context, file *File, start, end int64, syncType SyncType) error { - var err error +func (f *overlayFileOperations) Fsync(ctx context.Context, file *File, start, end int64, syncType SyncType) (err error) { f.upperMu.Lock() if f.upper != nil { err = f.upper.FileOperations.Fsync(ctx, f.upper, start, end, syncType) } f.upperMu.Unlock() - if f.lower != nil { + if err == nil && f.lower != nil { // N.B. Fsync on the lower filesystem can cause writes of file // attributes (i.e. access time) despite the fact that we must // treat the lower filesystem as read-only. @@ -277,15 +300,14 @@ func (f *overlayFileOperations) Fsync(ctx context.Context, file *File, start, en } // Flush implements FileOperations.Flush. -func (f *overlayFileOperations) Flush(ctx context.Context, file *File) error { +func (f *overlayFileOperations) Flush(ctx context.Context, file *File) (err error) { // Flush whatever handles we have. - var err error f.upperMu.Lock() if f.upper != nil { err = f.upper.FileOperations.Flush(ctx, f.upper) } f.upperMu.Unlock() - if f.lower != nil { + if err == nil && f.lower != nil { err = f.lower.FileOperations.Flush(ctx, f.lower) } return err @@ -329,6 +351,7 @@ func (*overlayFileOperations) ConfigureMMap(ctx context.Context, file *File, opt if !o.isMappableLocked() { return syserror.ENODEV } + // FIXME(jamieliu): This is a copy/paste of fsutil.GenericConfigureMMap, // which we can't use because the overlay implementation is in package fs, // so depending on fs/fsutil would create a circular dependency. Move |