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Fix data race in blob_saver

Browse Source 
After the `BlobSaver` job is submitted, the buffer can be released and
reused by another `FileSaver` even before `BlobSaver.Save` returns. That
FileSaver will the change `buf.Data` leading to wrong backup statistics.

Found by `go test -race ./...`:

WARNING: DATA RACE
Write at 0x00c0000784a0 by goroutine 41:
  github.com/restic/restic/internal/archiver.(*FileSaver).saveFile()
      /home/michael/Projekte/restic/restic/internal/archiver/file_saver.go:176 +0x789
  github.com/restic/restic/internal/archiver.(*FileSaver).worker()
      /home/michael/Projekte/restic/restic/internal/archiver/file_saver.go:242 +0x2af
  github.com/restic/restic/internal/archiver.NewFileSaver.func2()
      /home/michael/Projekte/restic/restic/internal/archiver/file_saver.go:88 +0x5d
  golang.org/x/sync/errgroup.(*Group).Go.func1()
      /home/michael/go/pkg/mod/golang.org/x/sync@v0.0.0-20210220032951-036812b2e83c/errgroup/errgroup.go:57 +0x91

Previous read at 0x00c0000784a0 by goroutine 29:
  github.com/restic/restic/internal/archiver.(*BlobSaver).Save()
      /home/michael/Projekte/restic/restic/internal/archiver/blob_saver.go:57 +0x1dd
  github.com/restic/restic/internal/archiver.(*BlobSaver).Save-fm()
      <autogenerated>:1 +0xac
  github.com/restic/restic/internal/archiver.(*FileSaver).saveFile()
      /home/michael/Projekte/restic/restic/internal/archiver/file_saver.go:191 +0x855
  github.com/restic/restic/internal/archiver.(*FileSaver).worker()
      /home/michael/Projekte/restic/restic/internal/archiver/file_saver.go:242 +0x2af
  github.com/restic/restic/internal/archiver.NewFileSaver.func2()
      /home/michael/Projekte/restic/restic/internal/archiver/file_saver.go:88 +0x5d
  golang.org/x/sync/errgroup.(*Group).Go.func1()
      /home/michael/go/pkg/mod/golang.org/x/sync@v0.0.0-20210220032951-036812b2e83c/errgroup/errgroup.go:57 +0x91
This commit is contained in:
Michael Eischer 2022-07-03 14:47:53 +02:00
parent b6a38d43b3
commit ce89018902
1 changed files with 3 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
internal/archiver/blob_saver.go
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@ -45,6 +45,8 @@ func (s *BlobSaver) TriggerShutdown() {
// Save stores a blob in the repo. It checks the index and the known blobs
// before saving anything. It takes ownership of the buffer passed in.
func (s *BlobSaver) Save(ctx context.Context, t restic.BlobType, buf *Buffer) FutureBlob {
// buf might be freed once the job was submitted, thus calculate the length now
length := len(buf.Data)
ch := make(chan saveBlobResponse, 1)
select {
case s.ch <- saveBlobJob{BlobType: t, buf: buf, ch: ch}:
@ -54,7 +56,7 @@ func (s *BlobSaver) Save(ctx context.Context, t restic.BlobType, buf *Buffer) Fu
return FutureBlob{ch: ch}
}
return FutureBlob{ch: ch, length: len(buf.Data)}
return FutureBlob{ch: ch, length: length}
}
// FutureBlob is returned by SaveBlob and will return the data once it has been processed.