linux-kernel - Re: [PATCH 24/32] vfs: syscall: Add fsopen() to prepare for superblock creation [ver #9]

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Date:   Thu, 12 Jul 2018 13:25:58 -0700
From:   Andy Lutomirski <luto@...capital.net>
To:     David Howells <dhowells@...hat.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Lutomirski <luto@...nel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Linux API <linux-api@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Jann Horn <jannh@...gle.com>
Subject: Re: [PATCH 24/32] vfs: syscall: Add fsopen() to prepare for superblock creation [ver #9]



> On Jul 12, 2018, at 1:23 PM, David Howells <dhowells@...hat.com> wrote:
> 
> Linus Torvalds <torvalds@...ux-foundation.org> wrote:
> 
>> Don't play games with override_creds. It's wrong.
>> 
>> You have to use file->f_creds - no games, no garbage.
> 
> You missed the point.
> 

> 
> My suggestion was to use override_creds() to impose the appropriate creds at
> the top, be that file->f_creds or fs_context->creds (they would be the same in
> any case).

I think it should be a new syscall and use current’s creds. No override needed.


> Btw, do we protect sysfs, debugfs, tracefs, procfs, etc. writes against
> splice?  Some of the things in debugfs are really icky, allowing you to muck
> directly with hardware.
> 

We try. It has been a perennial source of severe bugs.

This is part of why I’d like to see splice() be an opt in. Also, it’s a major step toward getting rid of set_fs().