51e60259e1
replaceFile created a temp file, which was guaranteed to not overlap with another temp file. However, makeAnnexLink then deleted that file, in preparation for making the symlink in its place. This caused a race, since some other replaceFile could create a temp file, using the same name! I was able to reproduce the race easily running git-annex add -J10 in a directory with 100 files (all with different contents). Some files would get ingested into the annex, but their annex links would fail to be added. There could be other situations where this same problem could occur. Perhaps when the assistant is adding a file, if the user manually also ran git-annex add. Perhaps in cases not involving adding a file. The new replaceFile makes a temprary directory, which is guaranteed to be unique, and doesn't make a temp file in there. makeAnnexLink can thus create the symlink without problem and the race is avoided. Audited all calls to replaceFile to make sure that the old behavior of providing an empty temp file was not relied on. The general problem of asking for a temp file and deleting it as part of the process of using it could reach beyond replaceFile. Did some quick audits and didn't find other cases of it. Probably only symlink creation stuff would tend to make that mistake, mostly.
42 lines
1.3 KiB
Haskell
42 lines
1.3 KiB
Haskell
{- git-annex file replacing
|
|
-
|
|
- Copyright 2013-2015 Joey Hess <id@joeyh.name>
|
|
-
|
|
- Licensed under the GNU GPL version 3 or higher.
|
|
-}
|
|
|
|
module Annex.ReplaceFile where
|
|
|
|
import Common.Annex
|
|
import Annex.Perms
|
|
import Utility.Tmp
|
|
|
|
{- Replaces a possibly already existing file with a new version,
|
|
- atomically, by running an action.
|
|
-
|
|
- The action is passed the name of temp file, in a temp directory,
|
|
- which it can write to, and once done the temp file is moved into place
|
|
- and anything else in the temp directory is deleted.
|
|
-
|
|
- The action can throw an IO exception, in which case the temp directory
|
|
- will be deleted, and the existing file will be preserved.
|
|
-
|
|
- Throws an IO exception when it was unable to replace the file.
|
|
-}
|
|
replaceFile :: FilePath -> (FilePath -> Annex ()) -> Annex ()
|
|
replaceFile file action = do
|
|
misctmpdir <- fromRepo gitAnnexTmpMiscDir
|
|
void $ createAnnexDirectory misctmpdir
|
|
let basetmp = takeFileName file
|
|
withTmpDirIn misctmpdir basetmp $ \tmpdir -> do
|
|
let tmpfile = tmpdir <> basetmp
|
|
action tmpfile
|
|
liftIO $ replaceFileFrom tmpfile file
|
|
|
|
replaceFileFrom :: FilePath -> FilePath -> IO ()
|
|
replaceFileFrom src dest = go `catchIO` fallback
|
|
where
|
|
go = moveFile src dest
|
|
fallback _ = do
|
|
createDirectoryIfMissing True $ parentDir dest
|
|
go
|