linux-kernel - Re: [PATCH 05/14] fs: don't allow kernel reads and writes without iter ops

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Date:   Wed, 14 Oct 2020 06:51:15 +0100
From:   Christoph Hellwig <hch@...radead.org>
To:     Alexander Viro <aviro@...hat.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Eric Biggers <ebiggers@...nel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Christoph Hellwig <hch@....de>,
        Michael Ellerman <mpe@...erman.id.au>,
        the arch/x86 maintainers <x86@...nel.org>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH 05/14] fs: don't allow kernel reads and writes without
 iter ops

On Sat, Oct 10, 2020 at 01:55:24AM +0000, Alexander Viro wrote:
> FWIW, I hadn't pushed that branch out (or merged it into #for-next yet);
> for one thing, uml part (mconsole) is simply broken, for another...
> IMO ##5--8 are asking for kernel_pread() and if you look at binfmt_elf.c,
> you'll see elf_read() being pretty much that.  acct.c, keys and usermode
> parts are asking for kernel_pwrite() as well.
> 
> I've got stuck looking through the drivers/target stuff - it would've
> been another kernel_pwrite() candidate, but it smells like its use of
> filp_open() is really asking for trouble, starting with symlink attacks.
> Not sure - I'm not familiar with the area, but...

Can you just pull in the minimal fix so that the branch gets fixed
for this merge window?  All the cleanups can come later.