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Code Issues Releases Activity

h264: prevent decoding of slice NALs in extradata

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It is not posible to call get_buffer during frame-mt codec
initialization. Libavformat might pass huge amounts of data as
extradata after parsing broken files. The 'extradata' for the fuzzed
sample sample_varPAR_s5374_r001-02.avi is 2.8M large and contains
multiple slices.
This commit is contained in:
Janne Grunau 2012-12-15 22:21:23 +01:00
parent 26e4f0c70f
commit 61c6eef545
2 changed files with 23 additions and 7 deletions
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27
libavcodec/h264.c
View File

@ -954,7 +954,8 @@ fail:
return -1; // free_tables will clean up for us
}
static int decode_nal_units(H264Context *h, const uint8_t *buf, int buf_size);
static int decode_nal_units(H264Context *h, const uint8_t *buf, int buf_size,
int parse_extradata);
static av_cold void common_init(H264Context *h)
{
@ -1001,7 +1002,7 @@ int ff_h264_decode_extradata(H264Context *h)
nalsize = AV_RB16(p) + 2;
if (p - avctx->extradata + nalsize > avctx->extradata_size)
return -1;
if (decode_nal_units(h, p, nalsize) < 0) {
if (decode_nal_units(h, p, nalsize, 1) < 0) {
av_log(avctx, AV_LOG_ERROR,
"Decoding sps %d from avcC failed\n", i);
return -1;
@ -1014,7 +1015,7 @@ int ff_h264_decode_extradata(H264Context *h)
nalsize = AV_RB16(p) + 2;
if (p - avctx->extradata + nalsize > avctx->extradata_size)
return -1;
if (decode_nal_units(h, p, nalsize) < 0) {
if (decode_nal_units(h, p, nalsize, 1) < 0) {
av_log(avctx, AV_LOG_ERROR,
"Decoding pps %d from avcC failed\n", i);
return -1;
@ -1025,7 +1026,7 @@ int ff_h264_decode_extradata(H264Context *h)
h->nal_length_size = (avctx->extradata[4] & 0x03) + 1;
} else {
h->is_avc = 0;
if (decode_nal_units(h, avctx->extradata, avctx->extradata_size) < 0)
if (decode_nal_units(h, avctx->extradata, avctx->extradata_size, 1) < 0)
return -1;
}
return 0;
@ -3708,7 +3709,8 @@ static int execute_decode_slices(H264Context *h, int context_count)
return 0;
}
static int decode_nal_units(H264Context *h, const uint8_t *buf, int buf_size)
static int decode_nal_units(H264Context *h, const uint8_t *buf, int buf_size,
int parse_extradata)
{
MpegEncContext *const s = &h->s;
AVCodecContext *const avctx = s->avctx;
@ -3831,6 +3833,17 @@ static int decode_nal_units(H264Context *h, const uint8_t *buf, int buf_size)
continue;
again:
/* Ignore every NAL unit type except PPS and SPS during extradata
* parsing. Decoding slices is not possible in codec init
* with frame-mt */
if (parse_extradata && HAVE_THREADS &&
(s->avctx->active_thread_type & FF_THREAD_FRAME) &&
(hx->nal_unit_type != NAL_PPS &&
hx->nal_unit_type != NAL_SPS)) {
av_log(avctx, AV_LOG_INFO, "Ignoring NAL unit %d during "
"extradata parsing\n", hx->nal_unit_type);
hx->nal_unit_type = NAL_FF_IGNORE;
}
err = 0;
switch (hx->nal_unit_type) {
case NAL_IDR_SLICE:
@ -3953,6 +3966,8 @@ again:
case NAL_SPS_EXT:
case NAL_AUXILIARY_SLICE:
break;
case NAL_FF_IGNORE:
break;
default:
av_log(avctx, AV_LOG_DEBUG, "Unknown NAL code: %d (%d bits)\n",
hx->nal_unit_type, bit_length);
@ -4049,7 +4064,7 @@ out:
return buf_index;
}
buf_index = decode_nal_units(h, buf, buf_size);
buf_index = decode_nal_units(h, buf, buf_size, 0);
if (buf_index < 0)
return -1;

3
libavcodec/h264.h
View File

@ -112,7 +112,8 @@ enum {
NAL_END_STREAM,
NAL_FILLER_DATA,
NAL_SPS_EXT,
NAL_AUXILIARY_SLICE = 19
NAL_AUXILIARY_SLICE = 19,
NAL_FF_IGNORE = 0xff0f001,
};
/**