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avcodec/alsdec: Allow the user to set a maximum prediction order

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The only offical profile i could find (ALS simple profile) has a max of 15 while the bitstream allows 1023
which is very slow.

We do have a fate sample with 1023

Fixes: Timeout
Fixes: 429645375/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ALS_fuzzer-5377900448907264

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
2025-07-22 02:56:27 +02:00
parent 0a108a37e1
commit 0887d2e291
1 changed files with 20 additions and 0 deletions
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20
libavcodec/alsdec.c
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@ -38,6 +38,7 @@
#include "internal.h"
#include "mlz.h"
#include "libavutil/mem.h"
#include "libavutil/opt.h"
#include "libavutil/samplefmt.h"
#include "libavutil/crc.h"
#include "libavutil/softfloat_ieee754.h"
@ -194,6 +195,7 @@ typedef struct ALSChannelData {
typedef struct ALSDecContext {
AVClass *av_class;
AVCodecContext *avctx;
ALSSpecificConfig sconf;
GetBitContext gb;
@ -239,6 +241,7 @@ typedef struct ALSDecContext {
unsigned char *larray; ///< buffer to store the output of masked lz decompression
int *nbits; ///< contains the number of bits to read for masked lz decompression for all samples
int highest_decoded_channel;
int user_max_order; ///< user specified maximum prediction order
} ALSDecContext;
@ -352,6 +355,11 @@ static av_cold int read_specific_config(ALSDecContext *ctx)
skip_bits(&gb, 5); // skip 5 reserved bits
skip_bits1(&gb); // skip aux_data_enabled
if (sconf->max_order > ctx->user_max_order) {
av_log(avctx, AV_LOG_ERROR, "order %d exceeds specified max %d\n", sconf->max_order, ctx->user_max_order);
return AVERROR_INVALIDDATA;
}
// check for ALSSpecificConfig struct
if (als_id != MKBETAG('A','L','S','\0'))
@ -2183,6 +2191,17 @@ static av_cold void flush(AVCodecContext *avctx)
ctx->frame_id = 0;
}
static const AVOption options[] = {
{ "max_order", "Sets the maximum order (ALS simple profile allows max 15)", offsetof(ALSDecContext, user_max_order), AV_OPT_TYPE_INT, { .i64 = 1023 }, 0, 1023, AV_OPT_FLAG_AUDIO_PARAM | AV_OPT_FLAG_DECODING_PARAM },
{ NULL }
};
static const AVClass als_class = {
.class_name = "als",
.item_name = av_default_item_name,
.option = options,
.version = LIBAVUTIL_VERSION_INT,
};
const FFCodec ff_als_decoder = {
.p.name = "als",
@ -2193,6 +2212,7 @@ const FFCodec ff_als_decoder = {
.init = decode_init,
.close = decode_end,
FF_CODEC_DECODE_CB(decode_frame),
.p.priv_class = &als_class,
.flush = flush,
.p.capabilities = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_CHANNEL_CONF,
.caps_internal = FF_CODEC_CAP_INIT_CLEANUP,