[FFmpeg-devel] [PATCH 1/2] avcodec: add mvdv video decoder

[Paul B Mahol]

On 11/26/19, Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:
> Am Di., 26. Nov. 2019 um 10:53 Uhr schrieb Paul B Mahol <onemda at gmail.com>:
>>
>> On 11/25/19, Tomas Härdin <tjoppen at acc.umu.se> wrote:
>> > mån 2019-11-25 klockan 22:09 +0100 skrev Paul B Mahol:
>> >> Signed-off-by: Paul B Mahol <onemda at gmail.com>
>> >> +static int decode_mvdv(MidiVidContext *s, AVCodecContext *avctx,
>> >> AVFrame
>> >> *frame)
>> >> +{
>> >> +    GetByteContext *gb = &s->gb;
>> >> +    GetBitContext mask;
>> >> +    GetByteContext idx9;
>> >> +    uint16_t nb_vectors, intra_flag;
>> >> +    const uint8_t *vec;
>> >> +    const uint8_t *mask_start;
>> >> +    uint8_t *skip;
>> >> +    int mask_size;
>> >> +    int idx9bits = 0;
>> >> +    int idx9val = 0;
>> >> +    int num_blocks;
>> >> +
>> >> +    nb_vectors = bytestream2_get_le16(gb);
>> >> +    intra_flag = bytestream2_get_le16(gb);
>> >> +    if (intra_flag) {
>> >> +        num_blocks = (avctx->width / 2) * (avctx->height / 2);
>> >
>> > Will UB if width*height/4 > INT_MAX
>> >
>> >> +    } else {
>> >> +        int skip_linesize;
>> >> +
>> >> +        num_blocks = bytestream2_get_le32(gb);
>> >
>> > Might want to use uint32_t so this doesn't lead to weirdness on 32-bit
>> >
>> >> +        skip_linesize = avctx->width >> 1;
>> >> +        mask_start = gb->buffer_start + bytestream2_tell(gb);
>> >> +        mask_size = (avctx->width >> 5) * (avctx->height >> 2);
>> >
>> > This can also UB
>
>> Nothing of this can actually happen.
>
> Then you could add asserts (and cut your quotes).

Asserts for checking UBs? Non sense.

>
> Carl Eugen
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