DAV files may contain a variable length padding in between chunks
filled with 0xff bytes. The current skipping logic is incorrect as it
may skip over DHAV chunks not appearing sequentially in the file.
We now look for the 'DHAV' tag using a byte-by-byte search in order
to handle such situations. Also the dhav->last_good_pos field will
not be updated while skipping unrecognized data.
Fixes: signed integer overflow: 9223372036854775807 + 32768 cannot be represented in type 'long'
Fixes: 27744/clusterfuzz-testcase-minimized-ffmpeg_dem_DHAV_fuzzer-5179319491756032
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
Those are private fields, no reason to have them exposed in a public
header. Since there are some (semi-)public fields located after these,
even though this section is supposed to be private, keep some dummy
padding there until the next major bump to preserve ABI compatibility.
