[PATCH 03/11] fs: don't allow splice read/write without explicit ops

[Kees Cook]

On Mon, Aug 17, 2020 at 09:32:04AM +0200, Christoph Hellwig wrote:
> default_file_splice_write is the last piece of generic code that uses
> set_fs to make the uaccess routines operate on kernel pointers.  It
> implements a "fallback loop" for splicing from files that do not actually
> provide a proper splice_read method.  The usual file systems and other
> high bandwith instances all provide a ->splice_read, so this just removes
> support for various device drivers and procfs/debugfs files.  If splice
> support for any of those turns out to be important it can be added back
> by switching them to the iter ops and using generic_file_splice_read.
> 
> Signed-off-by: Christoph Hellwig <hch at lst.de>

This seems a bit disruptive? I feel like this is going to make fuzzers
really noisy (e.g. trinity likes to splice random stuff out of /sys and
/proc).

Conceptually, though:

Reviewed-by: Kees Cook <keescook at chromium.org>

-- 
Kees Cook