[PATCH] os: Make sure big requests have sufficient length.

[Eric Anholt]

Michal Srb <msrb at suse.com> writes:

> Here is a script that can be used to crash X server using a broken big request 
> for PolyLine. It connects to DISPLAY=:1 and doesn't support authentication. 
> Look inside the script for more details.
>
> Other requests could be used to crash X server in similar way, for example 
> SetFontPath.

I noticed this still in my mailbox.  I tried writing an mergeable unit
test for it at:

https://github.com/anholt/xserver/commit/d0e9d732750aa8eb7eeb33adce321f1dfeef265d

but it doesn't manage to crash the server because I can't set the endian
mode using xcb (and xcb, sensibly, doesn't let me get an fd without
doing connection setup on it).

I don't know much about the codepath with the bug, but hopefully this
sparks some discussion.
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