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FFmpeg/libavcodec/vp9_superframe_bsf.c
Andreas Rheinhardt c12e8c97b1 avcodec/vp9_superframe_bsf: Check for existence of data before reading it
Packets without data need to be handled specially in order to avoid
undefined reads. Pass these packets through unchanged in case there
are no cached packets* and error out in case there are cached packets:
Returning the packet would mess with the order of the packets;
if one returned the zero-sized packet before the superframe that will
be created from the packets in the cache, the zero-sized packet would
overtake the packets in the cache; if one returned the packet later,
the packets that complete the superframe will overtake the zero-sized
packet.

*: This case e.g. encompasses the scenario of updated extradata
side-data at the end.

Fixes: Out of array read
Fixes: 45722/clusterfuzz-testcase-minimized-ffmpeg_BSF_VP9_SUPERFRAME_fuzzer-5173378975137792

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
2022-03-31 10:48:50 +02:00

232 lines
5.9 KiB
C

/*
* Vp9 invisible (alt-ref) frame to superframe merge bitstream filter
* Copyright (c) 2016 Ronald S. Bultje <rsbultje@gmail.com>
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "libavutil/avassert.h"
#include "bsf.h"
#include "bsf_internal.h"
#include "get_bits.h"
#define MAX_CACHE 8
typedef struct VP9BSFContext {
int n_cache;
AVPacket *cache[MAX_CACHE];
} VP9BSFContext;
static void stats(AVPacket * const *in, int n_in,
unsigned *_max, unsigned *_sum)
{
int n;
unsigned max = 0, sum = 0;
for (n = 0; n < n_in; n++) {
unsigned sz = in[n]->size;
if (sz > max)
max = sz;
sum += sz;
}
*_max = max;
*_sum = sum;
}
static int merge_superframe(AVPacket * const *in, int n_in, AVPacket *out)
{
unsigned max, sum, mag, marker, n, sz;
uint8_t *ptr;
int res;
stats(in, n_in, &max, &sum);
mag = av_log2(max) >> 3;
marker = 0xC0 + (mag << 3) + (n_in - 1);
sz = sum + 2 + (mag + 1) * n_in;
res = av_new_packet(out, sz);
if (res < 0)
return res;
ptr = out->data;
for (n = 0; n < n_in; n++) {
memcpy(ptr, in[n]->data, in[n]->size);
ptr += in[n]->size;
}
#define wloop(mag, wr) \
do { \
for (n = 0; n < n_in; n++) { \
wr; \
ptr += mag + 1; \
} \
} while (0)
// write superframe with marker 110[mag:2][nframes:3]
*ptr++ = marker;
switch (mag) {
case 0:
wloop(mag, *ptr = in[n]->size);
break;
case 1:
wloop(mag, AV_WL16(ptr, in[n]->size));
break;
case 2:
wloop(mag, AV_WL24(ptr, in[n]->size));
break;
case 3:
wloop(mag, AV_WL32(ptr, in[n]->size));
break;
}
*ptr++ = marker;
av_assert0(ptr == &out->data[out->size]);
return 0;
}
static int vp9_superframe_filter(AVBSFContext *ctx, AVPacket *pkt)
{
GetBitContext gb;
VP9BSFContext *s = ctx->priv_data;
int res, invisible, profile, marker, uses_superframe_syntax = 0, n;
res = ff_bsf_get_packet_ref(ctx, pkt);
if (res < 0)
return res;
if (!pkt->size) {
/* In case the cache is empty we can pass side-data-only packets
* through unchanged. Otherwise, such a packet makes no sense. */
if (!s->n_cache)
return 0;
res = AVERROR_INVALIDDATA;
goto done;
}
marker = pkt->data[pkt->size - 1];
if ((marker & 0xe0) == 0xc0) {
int nbytes = 1 + ((marker >> 3) & 0x3);
int n_frames = 1 + (marker & 0x7), idx_sz = 2 + n_frames * nbytes;
uses_superframe_syntax = pkt->size >= idx_sz && pkt->data[pkt->size - idx_sz] == marker;
}
if ((res = init_get_bits8(&gb, pkt->data, pkt->size)) < 0)
goto done;
get_bits(&gb, 2); // frame marker
profile = get_bits1(&gb);
profile |= get_bits1(&gb) << 1;
if (profile == 3) profile += get_bits1(&gb);
if (get_bits1(&gb)) {
invisible = 0;
} else {
get_bits1(&gb); // keyframe
invisible = !get_bits1(&gb);
}
if (uses_superframe_syntax && s->n_cache > 0) {
av_log(ctx, AV_LOG_ERROR,
"Mixing of superframe syntax and naked VP9 frames not supported\n");
res = AVERROR(ENOSYS);
goto done;
} else if ((!invisible || uses_superframe_syntax) && !s->n_cache) {
// passthrough
return 0;
} else if (s->n_cache + 1 >= MAX_CACHE) {
av_log(ctx, AV_LOG_ERROR,
"Too many invisible frames\n");
res = AVERROR_INVALIDDATA;
goto done;
}
av_packet_move_ref(s->cache[s->n_cache++], pkt);
if (invisible) {
return AVERROR(EAGAIN);
}
av_assert0(s->n_cache > 0);
// build superframe
if ((res = merge_superframe(s->cache, s->n_cache, pkt)) < 0)
goto done;
res = av_packet_copy_props(pkt, s->cache[s->n_cache - 1]);
if (res < 0)
goto done;
for (n = 0; n < s->n_cache; n++)
av_packet_unref(s->cache[n]);
s->n_cache = 0;
done:
if (res < 0)
av_packet_unref(pkt);
return res;
}
static int vp9_superframe_init(AVBSFContext *ctx)
{
VP9BSFContext *s = ctx->priv_data;
int n;
// alloc cache packets
for (n = 0; n < MAX_CACHE; n++) {
s->cache[n] = av_packet_alloc();
if (!s->cache[n])
return AVERROR(ENOMEM);
}
return 0;
}
static void vp9_superframe_flush(AVBSFContext *ctx)
{
VP9BSFContext *s = ctx->priv_data;
int n;
// unref cached data
for (n = 0; n < s->n_cache; n++)
av_packet_unref(s->cache[n]);
s->n_cache = 0;
}
static void vp9_superframe_close(AVBSFContext *ctx)
{
VP9BSFContext *s = ctx->priv_data;
int n;
// free cached data
for (n = 0; n < MAX_CACHE; n++)
av_packet_free(&s->cache[n]);
}
static const enum AVCodecID codec_ids[] = {
AV_CODEC_ID_VP9, AV_CODEC_ID_NONE,
};
const FFBitStreamFilter ff_vp9_superframe_bsf = {
.p.name = "vp9_superframe",
.p.codec_ids = codec_ids,
.priv_data_size = sizeof(VP9BSFContext),
.filter = vp9_superframe_filter,
.init = vp9_superframe_init,
.flush = vp9_superframe_flush,
.close = vp9_superframe_close,
};