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From: Miklos Szeredi <miklos@szeredi.hu>
To: Chengguang Xu <cgxu519@mykernel.net>
Cc: overlayfs <linux-unionfs@vger.kernel.org>
Subject: Re: [RFC PATCH 2/2] ovl: enhance write permission check for writable open
Date: Wed, 21 Jul 2021 15:14:42 +0200	[thread overview]
Message-ID: <CAJfpegus1AKdqhLNwgLZA1PyRrUF_4VQuNnGbM+aYOYnSBjsmQ@mail.gmail.com> (raw)
In-Reply-To: <20210424140316.485444-2-cgxu519@mykernel.net>

On Sat, 24 Apr 2021 at 16:04, Chengguang Xu <cgxu519@mykernel.net> wrote:
>
> Check upper file's write permission when open on writable mode.

This should already be done in ovl_open() -> ovl_open_realfile() ->
open_with_fake_path() -> do_dentry_open().

Do you have a test case indicating that the writecount test is not working?

Thanks,
Miklos

>
> NOTE: lower files may be shared between differnt overlayfs instances,
> so we skip the check of lower file to avoid introducing interferes.
>
> Signed-off-by: Chengguang Xu <cgxu519@mykernel.net>
> ---
>  fs/overlayfs/file.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
> index 6e454a294046..1c3c24d07d01 100644
> --- a/fs/overlayfs/file.c
> +++ b/fs/overlayfs/file.c
> @@ -144,12 +144,18 @@ static int ovl_real_fdget(const struct file *file, struct fd *real)
>  static int ovl_open(struct inode *inode, struct file *file)
>  {
>         struct file *realfile;
> +       struct inode *upperinode;
>         int err;
>
>         err = ovl_maybe_copy_up(file_dentry(file), file->f_flags);
>         if (err)
>                 return err;
>
> +       upperinode = ovl_inode_upper(inode);
> +       if (((file->f_mode & FMODE_WRITE) || file->f_flags & O_TRUNC) &&
> +           (upperinode && atomic_read(&upperinode->i_writecount) < 0))
> +               return -ETXTBSY;
> +
>         /* No longer need these flags, so don't pass them on to underlying fs */
>         file->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
>
> --
> 2.27.0
>
>

  reply	other threads:[~2021-07-21 13:14 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-24 14:03 [RFC PATCH 1/2] ovl: skip checking lower file's write permisson on truncate Chengguang Xu
2021-04-24 14:03 ` [RFC PATCH 2/2] ovl: enhance write permission check for writable open Chengguang Xu
2021-07-21 13:14   ` Miklos Szeredi [this message]
2021-04-28 12:18 ` 回复:[RFC PATCH 1/2] ovl: skip checking lower file's write permisson on truncate Chengguang Xu
2021-07-20 14:35 ` [RFC " Miklos Szeredi
2021-07-20 15:19   ` Miklos Szeredi
2021-07-20 16:01     ` Chengguang Xu
2021-07-20 16:01     ` Miklos Szeredi
2021-07-20 16:04       ` Chengguang Xu

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