Project: gpac (gpac/gpac), language: c++
Vulnerability instance: gpac.cve-2020-35981
Sanitizer: address

================= Bug Report (1/1) ==================
## Source: GitHub Issue
## URL: https://github.com/gpac/gpac/issues/1659
## Description:
Issue: gpac/gpac#1659
Title: A NULL pointer dereference in the function SetupWriters isomedia/isom_store.c:171
State: closed
Created by: Clingto
Created at: 2020-12-15 11:57:41+00:00

Issue Body:
System info:  
Ubuntu 16.04.6 LTS, X64, gcc 5.4.0, gpac (latest master c4f8bc6e and the latest V1.0.1 d8538e8)  

I think it is probably due to an imcomplete fix of  [#1485](https://github.com/gpac/gpac/issues/1485) 

Compile Command:
```
$ CC="gcc -fsanitize=address -g" CXX="g++ -fsanitize=address -g" ./configure --static-mp4box --extra-ldflags="-ldl -g"
$ make
```
Run Command:
```
$ MP4Box -hint $SetupWriters-null-pointer -out /dev/null 
```
POC file:  
https://github.com/Clingto/POC/blob/master/gpac-MP4Box/gpac-c4f8bc6e_poc/SetupWriters-null-pointer

gdb info:
```C
                                               
Program received signal SIGSEGV, Segmentation fault.
0x00000000005570be in SetupWriters ()
(gdb) bt
#0  0x00000000005570be in SetupWriters ()
#1  0x0000000000559c36 in WriteInterleaved ()
#2  0x000000000055a57f in WriteToFile ()
#3  0x000000000054d70f in gf_isom_write ()
#4  0x000000000054d893 in gf_isom_close ()
#5  0x00000000004171c3 in mp4boxMain ()
#6  0x00007ffff6ec7840 in __libc_start_main (main=0x409dc0 <main>, argc=5, argv=0x7fffffffdf78, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fffffffdf68) at ../csu/libc-start.c:291
#7  0x0000000000409df9 in _start ()


```
ASAN info:
```C
ASAN:SIGSEGV
=================================================================
==27206==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000028 (pc 0x000000778288 bp 0x7ffccf34fdd0 sp 0x7ffccf34fd40 T0)
    #0 0x778287 in SetupWriters isomedia/isom_store.c:171
    #1 0x77fd9c in WriteInterleaved isomedia/isom_store.c:1611
    #2 0x7811f2 in WriteToFile isomedia/isom_store.c:1885
    #3 0x75ba6e in gf_isom_write isomedia/isom_read.c:592
    #4 0x75bf43 in gf_isom_close isomedia/isom_read.c:616
    #5 0x42c0c0 in mp4boxMain /opt/data/yyp/fuzzsequence/test/0-day/SRC_asan/applications/mp4box/main.c:6718
    #6 0x7f218ddaf83f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2083f)
    #7 0x417638 in _start (/opt/data/yyp/fuzzsequence/test/0-day/SRC_asan/build/bin/MP4Box+0x417638)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV isomedia/isom_store.c:171 SetupWriters
==27206==ABORTING

```
Addition: This bug was found with our fuzzer, which is based on AFL. Our fuzzer is developed by Yuanpingyu(cfenicey@gmail.com) 、Xiangkun Jia(xiangkun@iscas.ac.cn) 、Marsman1996(lqliuyuwei@outlook.com) and Yanhao.


Build script:
#!/bin/bash -eu
# Minimized build script with only core build commands
set -eu
./configure --static-build --extra-cflags="${CFLAGS}" --extra-ldflags="${CFLAGS}"
make -j$(nproc)

Dockerfile:
FROM hwiwonlee/secb.base:latest
RUN apt-get update && apt-get install -y build-essential pkg-config libz-dev
RUN git clone https://github.com/gpac/gpac gpac
RUN git -C gpac checkout 96170ab9e525ff3db6d28e5ea6c5e6377ed3b9cf
WORKDIR $SRC/gpac
COPY build.sh $SRC/

Additional files:
filename: fuzz_parse.c
content: /* Copyright 2021 Google LLC
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
      http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
#include <stdio.h>
#include <unistd.h>

#include <gpac/internal/isomedia_dev.h>
#include <gpac/constants.h>

int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
    char filename[256];
    sprintf(filename, "/tmp/libfuzzer.%d", getpid());

    FILE *fp = fopen(filename, "wb");
    if (!fp) {
        return 0;
    }
    fwrite(data, size, 1, fp);
    fclose(fp);

    GF_ISOFile *movie = NULL;
    movie = gf_isom_open_file(filename, GF_ISOM_OPEN_READ_DUMP, NULL);
    if (movie != NULL) {
        gf_isom_close(movie);
    }
    unlink(filename);
    return 0;
}