Fixes: Timeout (too long -> 241ms) Fixes: 29083/clusterfuzz-testcase-minimized-ffmpeg_dem_SWF_fuzzer-6273684478230528
The source of the magic number is
A very quick simulation of the best case compression for "compress"
below is not nice written code as i did not expect I or anyone else
would ever see it again
I would have preferred some nicer expression or course, but thats
what it seems to be asymptotically. For smaller amounts of data a
tighter bound is possible but i saw no nice way to consider that
and it seems also overkill to try to do it more fine grained for
just this
main(){
int64_t bits = 0;
int bank = 256;
int bitbank = 8;
for(unsigned i = 0; i<1024*1024*1024*4U-100000;) {
int word_size = bank-255;
i += word_size;
bits += bitbank;
if (!(bank & (bank-1)))
bitbank ++;
bank++;
if (bitbank > 16) {
printf("BEST %f \n", 8.0 * i / bits );
bank = 256;
bitbank = 8;
}
}
}
above assumes i remembered correctly how the algorithm works but the
value was close to what actual compession of zeros gave
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>