avcodec/webp: Always set pix_fmt

Fixes: out of array access
Fixes: 1434/clusterfuzz-testcase-minimized-6314998085189632
Fixes: 1435/clusterfuzz-testcase-minimized-6483783723253760

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/targets/ffmpeg
Reviewed-by: "Ronald S. Bultje" <rsbultje@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
void inter_predict(VP8Context *s, VP8ThreadData *td, uint8_t *dst[3],
                   VP8Macroblock *mb, int mb_x, int mb_y)
{
    int x_off = mb_x << 4, y_off = mb_y << 4;
    int width = 16 * s->mb_width, height = 16 * s->mb_height;
    ThreadFrame *ref = &s->framep[mb->ref_frame]->tf;
    VP56mv *bmv = mb->bmv;

    switch (mb->partitioning) {
    case VP8_SPLITMVMODE_NONE:
        vp8_mc_part(s, td, dst, ref, x_off, y_off,
                    0, 0, 16, 16, width, height, &mb->mv);
        break;
    case VP8_SPLITMVMODE_4x4: {
        int x, y;
        VP56mv uvmv;

        /* Y */
        for (y = 0; y < 4; y++) {
            for (x = 0; x < 4; x++) {
                vp8_mc_luma(s, td, dst[0] + 4 * y * s->linesize + x * 4,
                            ref, &bmv[4 * y + x],
                            4 * x + x_off, 4 * y + y_off, 4, 4,
                            width, height, s->linesize,
                            s->put_pixels_tab[2]);
            }
        }

        /* U/V */
        x_off  >>= 1;
        y_off  >>= 1;
        width  >>= 1;
        height >>= 1;
        for (y = 0; y < 2; y++) {
            for (x = 0; x < 2; x++) {
                uvmv.x = mb->bmv[2 * y       * 4 + 2 * x    ].x +
                         mb->bmv[2 * y       * 4 + 2 * x + 1].x +
                         mb->bmv[(2 * y + 1) * 4 + 2 * x    ].x +
                         mb->bmv[(2 * y + 1) * 4 + 2 * x + 1].x;
                uvmv.y = mb->bmv[2 * y       * 4 + 2 * x    ].y +
                         mb->bmv[2 * y       * 4 + 2 * x + 1].y +
                         mb->bmv[(2 * y + 1) * 4 + 2 * x    ].y +
                         mb->bmv[(2 * y + 1) * 4 + 2 * x + 1].y;
                uvmv.x = (uvmv.x + 2 + FF_SIGNBIT(uvmv.x)) >> 2;
                uvmv.y = (uvmv.y + 2 + FF_SIGNBIT(uvmv.y)) >> 2;
                if (s->profile == 3) {
                    uvmv.x &= ~7;
                    uvmv.y &= ~7;
                }
                vp8_mc_chroma(s, td, dst[1] + 4 * y * s->uvlinesize + x * 4,
                              dst[2] + 4 * y * s->uvlinesize + x * 4, ref,
                              &uvmv, 4 * x + x_off, 4 * y + y_off, 4, 4,
                              width, height, s->uvlinesize,
                              s->put_pixels_tab[2]);
            }
        }
        break;
    }
    case VP8_SPLITMVMODE_16x8:
        vp8_mc_part(s, td, dst, ref, x_off, y_off,
                    0, 0, 16, 8, width, height, &bmv[0]);
        vp8_mc_part(s, td, dst, ref, x_off, y_off,
                    0, 8, 16, 8, width, height, &bmv[1]);
        break;
    case VP8_SPLITMVMODE_8x16:
        vp8_mc_part(s, td, dst, ref, x_off, y_off,
                    0, 0, 8, 16, width, height, &bmv[0]);
        vp8_mc_part(s, td, dst, ref, x_off, y_off,
                    8, 0, 8, 16, width, height, &bmv[1]);
        break;
    case VP8_SPLITMVMODE_8x8:
        vp8_mc_part(s, td, dst, ref, x_off, y_off,
                    0, 0, 8, 8, width, height, &bmv[0]);
        vp8_mc_part(s, td, dst, ref, x_off, y_off,
                    8, 0, 8, 8, width, height, &bmv[1]);
        vp8_mc_part(s, td, dst, ref, x_off, y_off,
                    0, 8, 8, 8, width, height, &bmv[2]);
        vp8_mc_part(s, td, dst, ref, x_off, y_off,
                    8, 8, 8, 8, width, height, &bmv[3]);
        break;
    }
}

void inter_predict(VP8Context *s, VP8ThreadData *td, uint8_t *dst[3],
                   VP8Macroblock *mb, int mb_x, int mb_y)
{
    int x_off = mb_x << 4, y_off = mb_y << 4;
    int width = 16 * s->mb_width, height = 16 * s->mb_height;
    ThreadFrame *ref = &s->framep[mb->ref_frame]->tf;
    VP56mv *bmv = mb->bmv;

    switch (mb->partitioning) {
    case VP8_SPLITMVMODE_NONE:
        vp8_mc_part(s, td, dst, ref, x_off, y_off,
                    0, 0, 16, 16, width, height, &mb->mv);
        break;
    case VP8_SPLITMVMODE_4x4: {
        int x, y;
        VP56mv uvmv;

        /* Y */
        for (y = 0; y < 4; y++) {
            for (x = 0; x < 4; x++) {
                vp8_mc_luma(s, td, dst[0] + 4 * y * s->linesize + x * 4,
                            ref, &bmv[4 * y + x],
                            4 * x + x_off, 4 * y + y_off, 4, 4,
                            width, height, s->linesize,
                            s->put_pixels_tab[2]);
            }
        }

        /* U/V */
        x_off  >>= 1;
        y_off  >>= 1;
        width  >>= 1;
        height >>= 1;
        for (y = 0; y < 2; y++) {
            for (x = 0; x < 2; x++) {
                uvmv.x = mb->bmv[2 * y       * 4 + 2 * x    ].x +
                         mb->bmv[2 * y       * 4 + 2 * x + 1].x +
                         mb->bmv[(2 * y + 1) * 4 + 2 * x    ].x +
                         mb->bmv[(2 * y + 1) * 4 + 2 * x + 1].x;
                uvmv.y = mb->bmv[2 * y       * 4 + 2 * x    ].y +
                         mb->bmv[2 * y       * 4 + 2 * x + 1].y +
                         mb->bmv[(2 * y + 1) * 4 + 2 * x    ].y +
                         mb->bmv[(2 * y + 1) * 4 + 2 * x + 1].y;
                uvmv.x = (uvmv.x + 2 + FF_SIGNBIT(uvmv.x)) >> 2;
                uvmv.y = (uvmv.y + 2 + FF_SIGNBIT(uvmv.y)) >> 2;
                if (s->profile == 3) {
                    uvmv.x &= ~7;
                    uvmv.y &= ~7;
                }
                vp8_mc_chroma(s, td, dst[1] + 4 * y * s->uvlinesize + x * 4,
                              dst[2] + 4 * y * s->uvlinesize + x * 4, ref,
                              &uvmv, 4 * x + x_off, 4 * y + y_off, 4, 4,
                              width, height, s->uvlinesize,
                              s->put_pixels_tab[2]);
            }
        }
        break;
    }
    case VP8_SPLITMVMODE_16x8:
        vp8_mc_part(s, td, dst, ref, x_off, y_off,
                    0, 0, 16, 8, width, height, &bmv[0]);
        vp8_mc_part(s, td, dst, ref, x_off, y_off,
                    0, 8, 16, 8, width, height, &bmv[1]);
        break;
    case VP8_SPLITMVMODE_8x16:
        vp8_mc_part(s, td, dst, ref, x_off, y_off,
                    0, 0, 8, 16, width, height, &bmv[0]);
        vp8_mc_part(s, td, dst, ref, x_off, y_off,
                    8, 0, 8, 16, width, height, &bmv[1]);
        break;
    case VP8_SPLITMVMODE_8x8:
        vp8_mc_part(s, td, dst, ref, x_off, y_off,
                    0, 0, 8, 8, width, height, &bmv[0]);
        vp8_mc_part(s, td, dst, ref, x_off, y_off,
                    8, 0, 8, 8, width, height, &bmv[1]);
        vp8_mc_part(s, td, dst, ref, x_off, y_off,
                    0, 8, 8, 8, width, height, &bmv[2]);
        vp8_mc_part(s, td, dst, ref, x_off, y_off,
                    8, 8, 8, 8, width, height, &bmv[3]);
        break;
    }
}
