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

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Message-ID: <202008181239.E51B80265@keescook>
Date:   Tue, 18 Aug 2020 12:39:34 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Christoph Hellwig <hch@....de>
Cc:     Al Viro <viro@...iv.linux.org.uk>,
        Michael Ellerman <mpe@...erman.id.au>, x86@...nel.org,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-arch@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 03/11] fs: don't allow splice read/write without explicit
 ops

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@....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@...omium.org>

-- 
Kees Cook