Potential DoS in mpeg4video parser

[jmaggard10]

Large zero-filled files can cause libavcodec to allocate very large quantities of RAM.

I ran across this when forked-daapd was scanning a directory that contained large pre-allocated files, but did not yet have any actual data in those files.

Reproduction is easy.

# truncate -s8G badfile.m4v
# ffprobe badfile.m4v

[michael]

You can limit the maximum for a single allocation by using -max_alloc X, most platforms also provide a way to limit the sum of all allocations of a process.
Its certainly possibly to limit the amount of allocated memory for a file of just zeros and maybe we should but, one can always create a file with a arbitrary large or long valid video which would need arbitrary amounts of memory to decode, thus i think theres not much better than a user specified limit that can be done here.

[cehoyos]

If there is an issue, it is not limited to the asp parser but can also be reproduced with at least the vc1, the h264, the hevc and with a little effort with the mpegvideo parser.

[cehoyos]

Please reopen if -max_alloc does not help.