oss-fuzz: heap-buffer-overflow on address 0x606000000060

reproduce with ./build-asan/tests/dav1d_fuzzer clusterfuzz-testcase-minimized-dav1d_fuzzer-5712491695308800

clusterfuzz-testcase-minimized-dav1d_fuzzer-5712491695308800

Error parsing OBU data
=================================================================
==16445==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x606000000060 at pc 0x7f589858cb17 bp 0x7ffc44b25490 sp 0x7ffc44b25480
READ of size 1 at 0x606000000060 thread T0
    #0 0x7f589858cb16 in dav1d_loopfilter_sbrow_16bpc ../src/lf_apply.c:185
    #1 0x7f58985ae493 in dav1d_filter_sbrow_16bpc ../src/recon.c:1459
    #2 0x7f5898501cd6 in dav1d_decode_frame ../src/decode.c:2669
    #3 0x7f5898505157 in dav1d_submit_frame ../src/decode.c:3036
    #4 0x7f58984d08cd in dav1d_parse_obus ../src/obu.c:1088
    #5 0x7f58985b02e7 in dav1d_decode ../src/lib.c:201
    #6 0x558632a86f6d in LLVMFuzzerTestOneInput ../tests/libfuzzer/dav1d_fuzzer.c:82
    #7 0x558632a8673f in main ../tests/libfuzzer/main.c:87
    #8 0x7f5897edcae6 in __libc_start_main (/lib64/libc.so.6+0x21ae6)
    #9 0x558632a86969 in _start (/home/janne/src/dav1d/build-asan/tests/dav1d_fuzzer+0x1969)

0x606000000060 is located 0 bytes to the right of 64-byte region [0x606000000020,0x606000000060) allocated by thread T0 here:
    #0 0x7f589890bd30 in malloc (/usr/lib/gcc/x86_64-pc-linux-gnu/7.3.0/libasan.so.4+0xded30)
    #1 0x7f58984ff97b in dav1d_decode_frame ../src/decode.c:2510

SUMMARY: AddressSanitizer: heap-buffer-overflow ../src/lf_apply.c:185 in dav1d_loopfilter_sbrow_16bpc
Shadow bytes around the buggy address:
  0x0c0c7fff7fb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c0c7fff7fc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c0c7fff7fd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c0c7fff7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c0c7fff7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c0c7fff8000: fa fa fa fa 00 00 00 00 00 00 00 00[fa]fa fa fa
  0x0c0c7fff8010: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c0c7fff8020: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c0c7fff8030: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c0c7fff8040: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c0c7fff8050: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==16445==ABORTING