Memory unsafety in withFilePath in 2.8.2.0

[bgamari]

Your environment

All.

Steps to reproduce

ghci> :set -XOverloadedStrings
ghci> import qualified Data.ByteString.Short as BSS
ghci> import Data.ByteString.Internal (c_strlen)
ghci> BSS.useAsCStringLen "ScriptEnv0.hs" $ \(ptr, len) -> c_strlen ptr >>= \clen -> print (clen, len)

Expected behaviour

(13,13)

Actual behaviour

ghci> :set -XOverloadedStrings
ghci> import qualified Data.ByteString.Short as BSS
ghci> import Data.ByteString.Internal (c_strlen)
ghci> BSS.useAsCStringLen "ScriptEnv0.hs" $ \(ptr, len) -> c_strlen ptr >>= \clen -> print (clen, len)
(13,13)
ghci> BSS.useAsCStringLen "ScriptEnv0.hs" $ \(ptr, len) -> c_strlen ptr >>= \clen -> print (clen, len)
(38,13)
ghci> BSS.useAsCStringLen "ScriptEnv0.hs" $ \(ptr, len) -> c_strlen ptr >>= \clen -> print (clen, len)
(29,13)
ghci> BSS.useAsCStringLen "ScriptEnv0.hs" $ \(ptr, len) -> c_strlen ptr >>= \clen -> print (clen, len)
(38,13)

This is due to https://github.com/haskell/unix/pull/279/files#diff-e155a859a7a42c152728c6296887607bcfe0a7b0213d98573053e137ed8ebb32R157, which incorrectly relies on strlen on a string produced with useCString. This was originally noted in haskell/cabal#9241.

[bgamari]

This is fixed in #294.

[gbaz]

Should the bytestring documentation be updated to more clearly warn about this footgun with the useAsCStringLen function?

[hasufell]

Fixed in #294

@Bodigrim are you making the 2.8.2.1 release?

[Bodigrim]

If you have a moment, please do, otherwise I'll release in the morning.

[hasufell]

https://hackage.haskell.org/package/unix-2.8.2.1

[hasufell]

@bgamari pushed tag for your submodules: https://github.com/haskell/unix/releases/tag/v2.8.2.1