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avcodec/jpeg2000dec: fix cdef remapping out-of-bounds write (CVE-2025-9951) #124

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avcodec/jpeg2000dec: fix cdef remapping out-of-bounds write (CVE-2025-9951) #124

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34 changes: 22 additions & 12 deletions libavcodec/jpeg2000dec.c
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Original file line number Diff line number Diff line change
Expand Up @@ -271,6 +271,25 @@ static int get_siz(Jpeg2000DecoderContext *s)
return AVERROR_INVALIDDATA;
}

for (i = 0; i < s->ncomponents; i++) {
if (s->cdef[i] < 0) {
for (i = 0; i < s->ncomponents; i++) {
s->cdef[i] = i + 1;
}
if ((s->ncomponents & 1) == 0)
s->cdef[s->ncomponents-1] = 0;
}
}
// after here we no longer have to consider negative cdef

int cdef_used = 0;
for (i = 0; i < s->ncomponents; i++)
cdef_used |= 1<<s->cdef[i];

// Check that the channels we have are what we expect for the number of components
if (cdef_used != ((int[]){0,2,3,14,15})[s->ncomponents])
return AVERROR_INVALIDDATA;

for (i = 0; i < s->ncomponents; i++) { // Ssiz_i XRsiz_i, YRsiz_i
uint8_t x = bytestream2_get_byteu(&s->g);
s->cbps[i] = (x & 0x7f) + 1;
Expand All @@ -283,7 +302,9 @@ static int get_siz(Jpeg2000DecoderContext *s)
av_log(s->avctx, AV_LOG_ERROR, "Invalid sample separation %d/%d\n", s->cdx[i], s->cdy[i]);
return AVERROR_INVALIDDATA;
}
log2_chroma_wh |= s->cdy[i] >> 1 << i * 4 | s->cdx[i] >> 1 << i * 4 + 2;
int i_remapped = s->cdef[i] ? s->cdef[i]-1 : (s->ncomponents-1);

log2_chroma_wh |= s->cdy[i] >> 1 << i_remapped * 4 | s->cdx[i] >> 1 << i_remapped * 4 + 2;
}

s->numXtiles = ff_jpeg2000_ceildiv(s->width - s->tile_offset_x, s->tile_width);
Expand Down Expand Up @@ -2853,17 +2874,6 @@ static int jpeg2000_decode_frame(AVCodecContext *avctx, AVFrame *picture,
if (ret = jpeg2000_read_bitstream_packets(s))
goto end;

for (int x = 0; x < s->ncomponents; x++) {
if (s->cdef[x] < 0) {
for (x = 0; x < s->ncomponents; x++) {
s->cdef[x] = x + 1;
}
if ((s->ncomponents & 1) == 0)
s->cdef[s->ncomponents-1] = 0;
break;
}
}

avctx->execute2(avctx, jpeg2000_decode_tile, picture, NULL, s->numXtiles * s->numYtiles);

jpeg2000_dec_cleanup(s);
Expand Down