Re: [PATCH] fuse: do not treat unlimited readdir count as a buffer size

[Miklos Szeredi]

On Tue, 28 Apr 2026 at 04:13, Matthew R. Ochs <mochs@xxxxxxxxxx> wrote:

> For virtiofs, the output kvec is included in the request bounce buffer
> allocated by copy_args_to_argbuf():
>
>   req->argbuf = kmalloc(len, GFP_ATOMIC);

Ugh.   The real bug here is inappropriate use of the bounce buffer.
fuse_readdir_uncached() should instead supply an array of pages.

It's a little more complicated, but would fix this properly: overlayfs
does want to get as much of the directory as possible in one go to be
most efficient.

I'd go with vmalloc -> alloc_pages_bulk, then vm_map_ram() before
parsing the result.

Thanks,
Miklos