[GHC] #7161: hSetNewlineMode and hSetEncoding can be performed on closed and semi-closed handles

[GHC]

#7161: hSetNewlineMode and hSetEncoding can be performed on closed and semi-closed
handles
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        Reporter:  duncan            |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.0.1
       Component:  Core Libraries    |              Version:  7.6.1-rc1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Changes (by thomie):

 * status:  infoneeded => new
 * cc: ekmett (added)


Old description:

> The `hSetNewlineMode` and `hSetEncoding` functions from
> `GHC/IO/Handle.hs` do not check that the Handle is in an open mode. It is
> possible to use them on closed handles. hSetEncoding on a closed Handle
> triggers a segfault. Similarly, the operations are also both possible on
> semi-closed handles, and given the way hGetContents is implemented, this
> will affect the result of hGetContents which is clearly against the
> intention of the hGetContents/semi-closed stuff.
>
> Both functions use the `withAllHandles__` helper. Unlike similar helpers
> like `wantReadableHandle_` this one doesn't do any handle mode checking.
>
> Additionally, `hSetBuffering` and `hSetBinary` mode also use the
> `withAllHandles__` pattern and don't obviously check for an open handle
> but I've not verified this.

New description:

 The `hSetNewlineMode` and `hSetEncoding` functions from `GHC/IO/Handle.hs`
 do not check that the Handle is in an open mode. It is possible to use
 them on closed handles. hSetEncoding on a closed Handle triggers a
 segfault. Similarly, the operations are also both possible on semi-closed
 handles, and given the way hGetContents is implemented, this will affect
 the result of hGetContents which is clearly against the intention of the
 hGetContents/semi-closed stuff.

 Both functions use the `withAllHandles__` helper. Unlike similar helpers
 like `wantReadableHandle_` this one doesn't do any handle mode checking.

 Additionally, `hSetBuffering` and `hSetBinaryMode` mode also use the
 `withAllHandles__` pattern and don't obviously check for an open handle
 but I've not verified this.

--

Comment:

 With or without segfaults, this could be fixed.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7161#comment:8>
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