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avcodec/dvbsubenc: Check nb_colors before using it

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Avoids a potential overflow when multiplying nb_colors by 6.
Also make the nb_colors check a bit more strict.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This commit is contained in:
Andreas Rheinhardt
2025-04-16 11:03:53 +02:00
parent 3acc3b0b50
commit 3cf21217b5
1 changed files with 5 additions and 6 deletions
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11
libavcodec/dvbsubenc.c
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@ -329,24 +329,23 @@ static int dvbsub_encode(AVCodecContext *avctx, uint8_t *outbuf, int buf_size,
if (h->num_rects) { if (h->num_rects) {
for (clut_id = 0; clut_id < h->num_rects; clut_id++) { for (clut_id = 0; clut_id < h->num_rects; clut_id++) {
if (buf_size < 6 + h->rects[clut_id]->nb_colors * 6)
return AVERROR_BUFFER_TOO_SMALL;
/* CLUT segment */ /* CLUT segment */
if (h->rects[clut_id]->nb_colors <= 4) { if (h->rects[clut_id]->nb_colors <= 4U) {
/* 2 bpp, some decoders do not support it correctly */ /* 2 bpp, some decoders do not support it correctly */
bpp_index = 0; bpp_index = 0;
} else if (h->rects[clut_id]->nb_colors <= 16) { } else if (h->rects[clut_id]->nb_colors <= 16U) {
/* 4 bpp, standard encoding */ /* 4 bpp, standard encoding */
bpp_index = 1; bpp_index = 1;
} else if (h->rects[clut_id]->nb_colors <= 256) { } else if (h->rects[clut_id]->nb_colors <= 256U) {
/* 8 bpp, standard encoding */ /* 8 bpp, standard encoding */
bpp_index = 2; bpp_index = 2;
} else { } else {
return AVERROR(EINVAL); return AVERROR(EINVAL);
} }
if (buf_size < 6 + h->rects[clut_id]->nb_colors * 6)
return AVERROR_BUFFER_TOO_SMALL;
/* CLUT segment */ /* CLUT segment */
*q++ = 0x0f; /* sync byte */ *q++ = 0x0f; /* sync byte */