Re: [FFmpeg-devel] [PATCH 00/22] Deprecate av_uninit

[Nicolas George <george@nsup.org>]

Zhao Zhili (HE12025-04-11):
> From: Zhao Zhili <zhilizhao@tencent.com>
> 
> The macro is meant to suppress false uninitialized warnings. However,
> sometimes these 'false uninitialized warnings' are really undefined
> behavior, and leading to real issue like crash, e.g., ab792634197e.
> 
> For false uninitialized warnings, it can be silenced by initialization,
> and compiler can easily optimize away unnecessary initializations.
> 
> av_uninit shouldn't be used in any case.

NAK, you are hiding the UBs, not fixing the bugs.

If the author of the code put av_uninit, that means they believe the
value will always have been initialized by the part of the code
responsible for it. If that is not true, then it is a bug that can lead
to an exploitable security issue or a silent data corruption.

With your changes, nothing proves that the = 0 you put there is the
right value, the bug is still there: the code expects the value to be
correctly set, but instead there is an arbitrary 0.

At least, with av_uninit, valgrind and fuzzing can find the bugs.

Regards,

-- 
  Nicolas George
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