Re: fuse, get_user_pages, flush_anon_page, aliasing caches and allthat again

[Miklos Szeredi]

> >
> >The root of the problem is that copy_to_user() may cause page faults
> >on the userspace buffer, and the page fault might (in case of a
> >maliciously crafted filesystem) recurse into the filesystem itself.
> 
> Would it be worthwhile to mlock the page? I know that needs root
> privs or some capability, but a static buffer could be put aside when
> fusermount is run.

And how would the kernel ensure, that the buffer supplied by userspace
is mlocked and stays mlocked during the memory copy?  I don't think
that would simplify the kerel side much, and would complicate the
userspace side considerably.

Miklos
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