Review Request 127834: ki18n: Fix theoretically possible use-after-free in gettext when using strict ANSI compilers

[Christoph Feck]

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This commit causes compilation failure:

ki18n/src/gettext.h:130:9: error: 'translation_found' was not declared in this scope
ki18n/src/gettext.h:180:9: error: 'translation_found' was not declared in this scope

- Christoph Feck


On May 7, 2016, 4:12 a.m., Michael Pyne wrote:
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> https://git.reviewboard.kde.org/r/127834/
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> (Updated May 7, 2016, 4:12 a.m.)
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> Review request for KDE Frameworks, Localization and Translation (l10n) and Chusslove Illich.
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> Repository: ki18n
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> Description
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> Coverity noted that some of code for message catalog lookup uses some pointer values after they are freed. Even though the use in question is a simple equality comparison against a different (valid) pointer, it is still undefined behavior according to the C (and C++) language specs and is therefore liable to cause miscompilation and who knows what other kinds of problems.
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> This code is not normally enabled, normally a code path that supports variable-length arrays is active, which is not susceptible to this bug.
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> Since VLAs are not supported even in current C++ versions, making VLA support mandatory is not feasible, so instead I opted to move the pointer comparisons to a point in the code where the comparison is valid, and then use the saved result later.
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> I have also reported the bug to GNU Gettext, since upstream still has the error. It is GNU Gettext bug 47847.
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> Diffs
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>   src/gettext.h b06fc90 
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> Diff: https://git.reviewboard.kde.org/r/127834/diff/
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> Testing
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> Code compiles and KDE applications still seem to work fine. I also tested with the changed code path forcibly enabled by disabling VLA support, and things still seemed to work.
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> There's not a lot of autotests to choose from, but the KLocalizedString test still passed.
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> Thanks,
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> Michael Pyne
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