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Win32 OTTD2FS/FS2OTTD used from multiple threads but use a static buffer #8713

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JGRennison opened this issue Feb 21, 2021 · 1 comment
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@JGRennison
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@JGRennison JGRennison commented Feb 21, 2021

Version of OpenTTD

master

Expected result

No thread safety issues

Actual result

The OTTD2FS/FS2OTTD functions are used in a wide variety of places in the codebase, including indirectly from non-main threads. (e.g. file scanner thread, network threads when debug output is on, crash logger). Various macros also use these functions (e.g. fopen, MB_TO_WIDE/WIDE_TO_MB, etc.).

On Win32, these methods use a static buffer, and return a pointer to that buffer.
In the event that the method is called from multiple threads in the same general time frame, callers could receive output from a different thread. Theoretically this could result in a buffer over-read if a thread is reading the buffer at the same time as another is in the middle of writing it.

I used TLS to make this go away: JGRennison/OpenTTD-patches@0a61671. std::string conversion could also be an option.

Steps to reproduce

I'm sure there must be a way of automatically detecting this on Windows.

@nielsmh
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@nielsmh nielsmh commented Feb 21, 2021

unix.cpp also appears to use a global iconv instance and global buffers.

nielsmh added a commit to nielsmh/OpenTTD that referenced this issue Feb 21, 2021
nielsmh added a commit to nielsmh/OpenTTD that referenced this issue Feb 21, 2021
nielsmh added a commit to nielsmh/OpenTTD that referenced this issue Feb 21, 2021
nielsmh added a commit to nielsmh/OpenTTD that referenced this issue Feb 21, 2021
nielsmh added a commit to nielsmh/OpenTTD that referenced this issue Feb 21, 2021
nielsmh added a commit to nielsmh/OpenTTD that referenced this issue Feb 23, 2021
nielsmh added a commit to nielsmh/OpenTTD that referenced this issue Apr 2, 2021
@nielsmh nielsmh closed this in e0561db Apr 7, 2021
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2 participants