Re: [PATCH] fuse: Add support for fuse stacked I/O

[Jann Horn]

2016-01-14 0:53 GMT+01:00 Nikhilesh Reddy <reddyn@xxxxxxxxxxxxxx>:
> Add support for filesystem stacked read/write of files
> when enabled through a userspace init option of FUSE_STACKED_IO.
>
> When FUSE_STACKED_IO is enabled all the reads and writes
> to the fuse mount point go directly to the native filesystem
> rather than through the fuse daemon. All requests that aren't
> read/write still go thought the userspace code.

Maybe I missed it, but how does this guard against kernel stack
overflow and how does it interact with the "sb->s_stack_depth >
FILESYSTEM_MAX_STACK_DEPTH" stacking limit that overlayfs and ecryptfs
use?

As far as I can tell from a quick glance, someone could just stack
lots of FUSE files on top of each other and cause kernel stack
overflow that way, and that's nasty.