Guo, Yejun:
>
>
>> -----Original Message-----
>> From: ffmpeg-devel <ffmpeg-devel-boun...@ffmpeg.org> On Behalf Of
>> Andreas Rheinhardt
>> Sent: 2021年2月21日 9:41
>> To: ffmpeg-devel@ffmpeg.org
>> Cc: Andreas Rheinhardt <andreas.rheinha...@gmail.com>
>> Subject: [FFmpeg-devel] [PATCH 1/2] avcodec/movtextenc: Check for too many
>> styles
>>
>> The counter for the number of styles is written on two bytes, ergo anything >
>> UINT16_MAX is invalid. This also fixes a compiler warning because of a
>> tautologically true check on 64bit systems.
>>
>> Signed-off-by: Andreas Rheinhardt <andreas.rheinha...@gmail.com>
>> ---
>> A better solution would be to error out as soon as the byte length of a
>> subtitle
>> exceeds UINT16_MAX; yet for this one would have to modify all of ass_split to
>> allow the callbacks to return errors.
>>
>> libavcodec/movtextenc.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/libavcodec/movtextenc.c b/libavcodec/movtextenc.c index
>> 1bef21e0b9..cf30adbd0a 100644
>> --- a/libavcodec/movtextenc.c
>> +++ b/libavcodec/movtextenc.c
>> @@ -355,7 +355,7 @@ static int mov_text_style_start(MovTextContext *s)
>> StyleBox *tmp;
>>
>> // last style != defaults, end the style entry and start a new one
>> - if (s->count + 1 > SIZE_MAX / sizeof(*s->style_attributes) ||
>> + if (s->count + 1 > FFMIN(SIZE_MAX /
>> + sizeof(*s->style_attributes), UINT16_MAX) ||
>
> hi, logically, I think the result of FFMIN(SIZE_MAX /
> sizeof(*s->style_attributes), UINT16_MAX) is always UINT16_MAX, we may just
> use 's->count + 1 > UINT16_MAX'.
>
And why?
>
>> !(tmp = av_fast_realloc(s->style_attributes,
>>
>> &s->style_attributes_bytes_allocated,
>> (s->count + 1) *
>> sizeof(*s->style_attributes)))) {
>> --
>> 2.27.0
>>
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