Ladybird: "Too many open files" in ImageDecoder when visiting Berkeley Mono website

[awesomekling]

To reproduce, open https://berkeleygraphics.com/typefaces/berkeley-mono/

After a short time, this error shows up:

342154.967 ImageDecoder(1431722): IPC::ConnectionBase::handle_messages: dup: Too many open files (errno=24)

There's a pretty huge GIF animation with 708(!) frames on the page, seems likely to be related :sweat_smile:

[ADKaster]

As mentioned on discord, we apparently create a separate memfd-backed anonymous buffer for each frame of animated gifs when interacting with ImageDecoder.

https://github.com/SerenityOS/serenity/blob/333454456b9150d9efb8697d6d314bb5a6a06108/Userland/Services/ImageDecoder/ImageDecoderServer.ipc#L6

With a 708 frame gif, that means we create 708 file descriptors, just for the one gif on the page. It's not surprising we hit the per-process fd limit that way.

We should refactor the way Gifs or other animated image formats are handled in ImageDecoder to not use so many dang file descriptors.

[nico]

Isn't the ulimit for fds on Linux many thousands?

[ADKaster]

In a bash session on my ubuntu 22.04 machine, it's 1024

$ ulimit -n
1024

[nico]

That's the soft limit though. Could setrlimit that up by 10x as a short-term fix :)

[ADKaster]

With the merging of https://github.com/SerenityOS/serenity/pull/24025 this issue becomes a bit more pressing. The current max number of fds that can be transferred at a time is 64. This limits gifs to 64 frames. The absolute max on linux for SCM_RIGHTS fd passing is 253, according to the man pages.