copyFile opens the file without setting cloexec

[joeyh]

copyFile opens a temporary file without setting the close-on-exec flag. So if another thread execs a process at the same time, the process can inherit an open FD to a temp file. Specifically, in withReplacementFile, it uses OS.openBinaryTempFile.

copyFileWithMetadata and copyFileToHandle had this same problem fixed in commit 0ff4e13

[joeyh]

I've requested that file-io provide a openBinaryTempFileWithCloseOnExec, which would make it easy to fix this problem. haskell/file-io#44

[roman-smrz]

I just want to note that I've also been affected by this behavior. In the end, I needed to replace the copyFile function with custom implementation, as it seems the current version is just not safe to use when executing other programs (at least not without lot of synchronization around).