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

[Nikhilesh Reddy]

On 01/18/2016 07:07 PM, Jann Horn wrote:
> 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.
Hi
Thanks so much for your comment and for catching this.
I have fixed the code to prevent further stacking and will send it out 
in the updated version of the patch ( now called fuse passthrough ).

--
Thanks
Nikhilesh Reddy

Qualcomm Innovation Center, Inc.
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