linux-kernel - Re: [PATCH 02/11] 9p: fix dentry leak in v9fs_vfs_atomic_open

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Date:	Wed, 18 Sep 2013 10:55:09 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	Linux-Fsdevel <linux-fsdevel@...r.kernel.org>,
	Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"mszeredi@...e.cz" <mszeredi@...e.cz>,
	Eric Van Hensbergen <ericvh@...il.com>,
	"M. Mohan Kumar" <mohan@...ibm.com>, stable@...r.kernel.org
Subject: Re: [PATCH 02/11] 9p: fix dentry leak in v9fs_vfs_atomic_open_dotl()

On Tue, Sep 17, 2013 at 11:23 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
> On Tue, Sep 17, 2013 at 05:36:49PM +0200, Miklos Szeredi wrote:
>> On Tue, Sep 17, 2013 at 1:44 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
>> > On Tue, Sep 17, 2013 at 12:16:56PM +0200, Miklos Szeredi wrote:
>> >
>> >> Just one. This needs to be removed, since this condition is now
>> >> explicitly allowed and later checked for:
>> >>
>> >>     if (WARN_ON(excl && !(*opened & FILE_CREATED)))
>> >>         *opened |= FILE_CREATED;
>> >
>> > D'oh...  Fixed and pushed.
>>
>> Okay, but moving the fsnotify_create()  to after the no-open section
>> is wrong, I think,  It's needed for the case of ->atomic_open() doing
>> lookup/create/no_open too.
>
> What a mess...  It's actually even uglier than that - which dentry should
> we pass to fsnotify_create() in case where finish_no_open() has been given
> a non-NULL dentry other than one we had passed to ->atomic_open()?  I think
> that version in mainline is actually broken in that respect as far as fuse
> is concerned, not that anybody sane could expect ...notify to work on fuse.

Yeah, your version is definitely nicer.  The correctness of the old
version could be argued thus:  if FILE_CREATED was set, then the file
didn't exist before, so there's no sense in reusing or allocating
another dentry.  But yes, the API allows it.

Thanks,
Miklos
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