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avcodec/dvdsubdec: Check for fully transparent rectangles earlier

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Testcase with large transparent rectangles changes from 67 sec to 3 sec decode time

Fixes: Timeout
Fixes: 8728/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_DVDSUB_fuzzer-5190088756559872

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Michael Niedermayer 2018-06-30 23:34:14 +02:00
parent 06a8d7ff00
commit d24c9e55f6
1 changed files with 14 additions and 7 deletions
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21
libavcodec/dvdsubdec.c
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@ -42,6 +42,7 @@ typedef struct DVDSubContext
uint8_t buf[0x10000];
int buf_size;
int forced_subs_only;
uint8_t used_color[256];
#ifdef DEBUG
int sub_id;
#endif
@ -100,7 +101,7 @@ static int decode_run_8bit(GetBitContext *gb, int *color)
return len;
}
static int decode_rle(uint8_t *bitmap, int linesize, int w, int h,
static int decode_rle(uint8_t *bitmap, int linesize, int w, int h, uint8_t used_color[256],
const uint8_t *buf, int start, int buf_size, int is_8bit)
{
GetBitContext gb;
@ -129,6 +130,7 @@ static int decode_rle(uint8_t *bitmap, int linesize, int w, int h,
len = decode_run_2bit(&gb, &color);
len = FFMIN(len, w - x);
memset(d + x, color, len);
used_color[color] = 1;
x += len;
if (x >= w) {
y++;
@ -370,7 +372,7 @@ static int decode_dvd_subtitles(DVDSubContext *ctx, AVSubtitle *sub_header,
h = 0;
if (w > 0 && h > 1) {
reset_rects(sub_header);
memset(ctx->used_color, 0, sizeof(ctx->used_color));
sub_header->rects = av_mallocz(sizeof(*sub_header->rects));
if (!sub_header->rects)
goto fail;
@ -381,10 +383,10 @@ static int decode_dvd_subtitles(DVDSubContext *ctx, AVSubtitle *sub_header,
bitmap = sub_header->rects[0]->data[0] = av_malloc(w * h);
if (!bitmap)
goto fail;
if (decode_rle(bitmap, w * 2, w, (h + 1) / 2,
if (decode_rle(bitmap, w * 2, w, (h + 1) / 2, ctx->used_color,
buf, offset1, buf_size, is_8bit) < 0)
goto fail;
if (decode_rle(bitmap + w, w * 2, w, h / 2,
if (decode_rle(bitmap + w, w * 2, w, h / 2, ctx->used_color,
buf, offset2, buf_size, is_8bit) < 0)
goto fail;
sub_header->rects[0]->data[1] = av_mallocz(AVPALETTE_SIZE);
@ -448,19 +450,24 @@ static int is_transp(const uint8_t *buf, int pitch, int n,
}
/* return 0 if empty rectangle, 1 if non empty */
static int find_smallest_bounding_rectangle(AVSubtitle *s)
static int find_smallest_bounding_rectangle(DVDSubContext *ctx, AVSubtitle *s)
{
uint8_t transp_color[256] = { 0 };
int y1, y2, x1, x2, y, w, h, i;
uint8_t *bitmap;
int transparent = 1;
if (s->num_rects == 0 || !s->rects || s->rects[0]->w <= 0 || s->rects[0]->h <= 0)
return 0;
for(i = 0; i < s->rects[0]->nb_colors; i++) {
if ((((uint32_t *)s->rects[0]->data[1])[i] >> 24) == 0)
if ((((uint32_t *)s->rects[0]->data[1])[i] >> 24) == 0) {
transp_color[i] = 1;
} else if (ctx->used_color[i])
transparent = 0;
}
if (transparent)
return 0;
y1 = 0;
while (y1 < s->rects[0]->h && is_transp(s->rects[0]->data[0] + y1 * s->rects[0]->linesize[0],
1, s->rects[0]->w, transp_color))
@ -595,7 +602,7 @@ static int dvdsub_decode(AVCodecContext *avctx,
return buf_size;
}
if (!is_menu && find_smallest_bounding_rectangle(sub) == 0)
if (!is_menu && find_smallest_bounding_rectangle(ctx, sub) == 0)
goto no_subtitle;
if (ctx->forced_subs_only && !(sub->rects[0]->flags & AV_SUBTITLE_FLAG_FORCED))