[FFmpeg-devel] [PATCH]lavc/truehd_core: Initialize the last bytes of the output buffer

[Carl Eugen Hoyos]

2019-02-14 22:08 GMT+01:00, James Almer <jamrial at gmail.com>:
> On 2/14/2019 5:59 PM, Carl Eugen Hoyos wrote:
>> 2019-02-12 12:58 GMT+01:00, Carl Eugen Hoyos <ceffmpeg at gmail.com>:
>>> Hi!
>>>
>>> The output of truehd_core is currently undeterministic, the last bytes
>>> are uninitialized, valgrind protests if less than 8 bytes are
>>> initialized.
>>> I believe attached patch is simpler than calculating the necessary
>>> write size at the bottom of the function.
>> New patch attached.
>>
>> Please comment, Carl Eugen
>>
>>
>> 0001-lavc-truehd_core-Initialize-the-last-bytes-of-the-ou.patch
>>
>> From f3e4231af54b7a7664e1a2224cc1223be683f93c Mon Sep 17 00:00:00 2001
>> From: Carl Eugen Hoyos <ceffmpeg at gmail.com>
>> Date: Thu, 14 Feb 2019 21:57:48 +0100
>> Subject: [PATCH] lavc/truehd_core: Initialize the last bytes of the output
>>  buffer.
>>
>> Avoids undeterministic output.
>> ---
>>  libavcodec/truehd_core_bsf.c |    2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/libavcodec/truehd_core_bsf.c b/libavcodec/truehd_core_bsf.c
>> index be021af..4760872 100644
>> --- a/libavcodec/truehd_core_bsf.c
>> +++ b/libavcodec/truehd_core_bsf.c
>> @@ -117,6 +117,8 @@ static int truehd_core_filter(AVBSFContext *ctx,
>> AVPacket *out)
>>          out->size -= reduce * 2;
>>          parity_nibble ^= out->size / 2;
>>
>> +        if (out_size > 8)
>> +            AV_ZERO64(out->data + out_size - 8);
>
> AV_ZERO# may use mmx instructions. It should be safe if no float ops are
> going to be used after it, otherwise an emms_c() will be needed and the
> performance hit may remove any gain you get from not using memset().

New patch with AV_WN64() attached.

Thank you, Carl Eugen
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