linux-kernel - Re: [PATCH v2 15/30] xfs: Define usercopy region in xfs

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Message-ID: <CAGXu5j+V-U4OTRoOoJNAQA30Em90j0FEUdd=Jt7UPxWUNxO0xg@mail.gmail.com>
Date:   Tue, 29 Aug 2017 11:55:20 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        David Windsor <dave@...lcore.net>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        linux-xfs@...r.kernel.org, Linux-MM <linux-mm@...ck.org>,
        "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH v2 15/30] xfs: Define usercopy region in xfs_inode slab cache

On Tue, Aug 29, 2017 at 1:14 AM, Christoph Hellwig <hch@...radead.org> wrote:
> One thing I've been wondering is wether we should actually just
> get rid of the online area.  Compared to reading an inode from
> disk a single additional kmalloc is negligible, and not having the
> inline data / extent list would allow us to reduce the inode size
> significantly.
>
> Kees/David:  how many of these patches are file systems with some
> sort of inline data?  Given that it's only about 30 patches declaring
> allocations either entirely valid for user copy or not might end up
> being nicer in many ways than these offsets.

9 filesystems use some form of inline data: xfs, vxfs, ufs, orangefs,
exofs, befs, jfs, ext2, and ext4. How much of each slab is whitelisted
varies by filesystem (e.g. ext2/4 uses i_data for other things, but
ufs and orangefs and have a dedicate field for symlink names).

-Kees

-- 
Kees Cook
Pixel Security