linux-kernel - Re: [GIT PULL] overlayfs update for 4.18

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Message-ID: <CAJfpeguG9urECaKoeiOBQLNyEFRFieg484ixWhaqtzhrGsASgQ@mail.gmail.com>
Date:   Mon, 11 Jun 2018 10:41:29 +0200
From:   Miklos Szeredi <miklos@...redi.hu>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        overlayfs <linux-unionfs@...r.kernel.org>
Subject: Re: [GIT PULL] overlayfs update for 4.18

On Sun, Jun 10, 2018 at 7:54 AM, Al Viro <viro@...iv.linux.org.uk> wrote:
> On Fri, Jun 08, 2018 at 11:52:08PM -0700, Christoph Hellwig wrote:
>> On Fri, Jun 08, 2018 at 02:13:30PM +0200, Miklos Szeredi wrote:
>> > Hi Linus,
>> >
>> > Please pull from:
>> >
>> >   git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs.git tags/ovl-update-4.18
>> >
>> > This contains two new features:
>> >
>> >  1) Stack file operations: this allows removal of several hacks from the
>> >     VFS, proper interaction of read-only open files with copy-up,
>> >     possibility to implement fs modifying ioctls properly, and others.
>>
>> Which includews all kinds of NAKed or at least non-acked VFS changes.
>
> Umm...  The worst of yours had been ->pre_mmap(), right?  He *did* drop that...
>
>> Please get these through Als tree after proper review first.
>
> OK, summary of sort (see fsdevel thread for details):
>         * path_open() is dubious; why not simply use vfsmount/dentry from the
> right layer when opening an underlying file?  Then it would be vfs_open()...
>         * ovl_mmap() is broken, plain and simple.  Failure ends up leaking
> a layer struct file *and* doing double fput() on overlayfs one.
>         * ovl_mmap() is also trivially DoSable - you can trigger tons and tons
> of reopens, each sticking a new (writable layer) struct file into a vma.
> We *do* want some scheme avoiding once-per-operations reopens in the
> copied-up-after-r/o-open case.  See possible kinda-sorta solution on fsdevel;
> I'm not sure I like it, though.

Al, thanks for the review.

Posted incremental for the ovl_mmap() issues to -fsdevel.  I'm pretty
confident that that addresses your comments.

Linus, would you still pull if Al's satisfied with that resolution?
I can post the fixes (just few liners) after the merge window.

I'm definitely not going to prepare another pull request this cycle if
the old one cannot be pulled.

Thanks,
Miklos