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

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Date:	Mon, 16 Sep 2013 21:03:25 +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 Mon, Sep 16, 2013 at 8:19 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
> On Mon, Sep 16, 2013 at 02:51:56PM +0200, Miklos Szeredi wrote:
>> From: Miklos Szeredi <mszeredi@...e.cz>
>>
>> commit b6f4bee02f "fs/9p: Fix atomic_open" fixed the O_EXCL behavior, but
>> results in a dentry leak if v9fs_vfs_lookup() returns non-NULL.
>
> Frankly, I would prefer to deal with that in fs/namei.c:atomic_open()
> instead.  I.e. let it call finish_no_open() as it used to do and
> turn
>                 if (create_error && dentry->d_inode == NULL) {
>                         error = create_error;
>                         goto out;
>                 }
> in fs/namei.c:atomic_open() into
>                 if (!dentry->d_inode) {
>                         if (create_error) {
>                                 error = create_error;
>                                 goto out;
>                         }
>                 } else if ((open_flag & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL)) {
>                         error = -EEXIST;
>                         goto out;
>                 }
>
> rather than try to deal with that crap in each instance of ->atomic_open()...
> Objections?

->atomic_open() could be any one of

 lookup
 lookup+create
 lookup+create+open

If it's the second one then the above is wrong.  Sure, we could check
FILE_CREATED as well, and if file wasn't created yet dentry is
positive then we return EEXIST.  But for that to be correct we need
the last patch in the series, preventing FILE_CREATED from being set
unconditionally.

Thanks,
Miklos
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